Hydrophilic PEG-grafted liquid-like surface: sliding or spreading

Hydrophilic PEG-grafted liquid-like surface: sliding or spreading | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hydrophilic PEG-grafted liquid-like surface: sliding or spreading Youfa zhang, Junxu Chen, Pengfei Zhang, Wei Wang, Weilin Deng, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6834931/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Study on counterintuitive hydrophilic liquid-like surface (LLS) remain in a nascent stage despite its exceptional application potential in interfacial engineering. Here, inspired by the inherent wetting heterogeneity of mPEG-silane, for the first time we discover a dynamic wettability switching mechanism in PEG-grafted LLS through solvation-coupled mechanical regulation of PEG brush conformations. Ordered methoxy-terminated brushes enable water droplet sliding (θ ≈ 33°), while disordered ether-exposed configurations induce spreading (θ ≈ 4°). This conformational control allows unprecedented spatial decoupling of condensation modes (dropwise vs filmwise) on homogeneous surfaces, with sliding-state LLS showing increase nucleation efficiency versus PDMS-grafted LLS. Notably, spreading-state surface achieves ultrafast underwater oil detachment (< 0.8 s) through synergistic hydration from dense ether groups and low friction from flexible brushes. Our findings establish molecular conformation engineering as a paradigm for designing multifunctional LLS with applications spanning smart thermal management, microfluidic systems, and novel anti-oil fouling coatings. Physical sciences/Chemistry/Materials chemistry/Soft materials/Polymers Physical sciences/Chemistry/Materials chemistry/Soft materials/Wetting Physical sciences/Chemistry/Materials chemistry/Soft materials/Self-assembly Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Liquid-like surfaces (LLSs), an emerging frontier in surface/interface science 1 , 2 , have garnered increasing attention owing to their exceptional liquid repellency, which does not rely on fragile texture 3 , 4 or low-retention lubricant 5 , 6 . Recent advances have focused primarily on omniphobic LLSs fabricated from materials such as polydimethylsiloxane(PDMS) 7 , 8 , perfluoropolyether(PFPE) 9 , 10 and flexible alkyl chains 11 , with applications spanning anti-fouling 12 , anti-scaling 13 , droplet transport 14 and oil-water separation 15 . However, hydrophilic LLSs remain understudied despite their significant potential. In contrast to omniphobic LLSs, hydrophilic LLSs exhibits counterintuitive wetting behavior, characterized by the coexistence of static hydrophilicity and dynamic hydrophobicity. The predominant approach of fabricating such LLSs in current literature involves the covalent immobilization of poly(ethylene glycol)(PEG) chains, typically methoxy-PEG-silane (mPEG-silane), to silica surfaces 16 . The inherent hydrophilicity of PEG-grafted LLSs originates from ether(-O-) groups in the polymer backbone, which enable strong hydration via hydrogen bonding with water molecules 17 , 18 . Moreover, the synergistic effect of flexible ether groups and terminal methoxy groups reduces the energy barrier for water droplet three-phase contact line motion, enabling ultralow contact angle hysteresis(CAH) 19 . In 2001, Papra et al. 16 first demonstrated ultrathin mPEG-silane-grafted surfaces with CAH below 3°. Following a nearly 20-year gap, Hozumi et al. 20 revitalized PEG-grafted LLS research by developing an innovative PEG-TEOS hybrid film that exhibiting CAH below 5° and good defrosting ability which potentially addresses the water-bridge effect in radiators. Whether the role of TEOS is as a binder or a nano-spacer 21 and the origin of the paradoxical wettability 19 , 22 have likewise been investigated by them. Intriguingly, these systems can achieve near-superhydrophilicity and suppress the coffee-ring effect upon alkaline treatment 23 . Further unprecedented observations include the dropwise condensation capability of PEG-grafted LLSs which exhibit superior heat transfer efficiency compared to conventional hydrophobic LLSs 24 , as well as anti-biofouling performance arising from PEG’s combined slipperiness and hydrophilicity 25 , 26 . These findings underscore the untapped potential of PEG-grafted LLSs, warranting deeper investigation into their latent functionalities. Building on the intrinsic heterogeneous wettability of PEG chains 1 , we demonstrate that PEG-grafted LLS exhibits reversible wettability switching between water droplet sliding and spreading under wet friction and water rinsing(Supplementary Scheme. 1). The Sum frequency generation (SFG) spectroscopy results show that the switching mechanism is mediated by the conformation changes of PEG chains by external forces. Beyond a critical shear force, conformational bending sterically occludes terminal methyl groups while exposes the ether groups, inducing surface reconstruction that promotes droplet spreading. In the absence of solvent plasticization, a mechanically rigid barrier forms that decouples applied shear forces from the chains, suppressing conformational switching. This regime only enhances droplet adhesion during droplet motion without substantially modifying the surface free energy (contact angle). Based on this unique wetting property, reversible switching between dropwise and filmwise condensation on material surfaces can be achieved solely by modulating the conformation of polymer brushes. Remarkably, for the first time we discovered that the densely packed ether groups endows the surface with robust hydration capability 27 – 29 , the reoriented PEG brushes (at spreading state) exhibited spontaneous oil detachment within 0.8s – this exceptional oil-repellency underwater suggests a new paradigm for designing high-performance anti-oilfouling surfaces. Results and discussion Wettability switching phenomena The fabrication of PEG-grafted LLS was accomplished via spin-coating deposition of mPEG-silane (Supplementary Fig. 1) ethanolic dispersions onto oxygen plasma-treated silica substrates, following a standardized protocol 20 . The observed C-O peak shift was consistent with established silanization mechanisms 24 (Supplementary Fig. 2). Systematic screening across PEG molecular weights (350–2000 Da) and concentrations (0.05–20 mM) revealed negligible CAH variations (Supplementary Fig. 3). The 750 Da mPEG-silane (9–12 ethylene oxide units) with 1mM concentration exhibited optimal performance, with minimal CAH (Δθ = 3.2°) and maximal droplet mobility ( v = 0.77 mm/s, 10 µL with tilting 5°), and was therefore selected for further characterization (Supplementary Fig. 4). Unlike previously reported toluene-based immersion methods 16 , 24 , 26 or tetraethyl orthosilicate (TEOS) crosslinking approaches 20 , 21 , 23 , the ethanol-assisted spin-coating technique produced an initially superhydrophilic surface (water contact angle = 3.1° in freshly prepared samples, defined as the spreading state ). This state displayed metastability, undergoing rapid transition to a slippery state upon exposure to water droplet rinsing, which hereafter is designated as the sliding state (Supplementary Fig. 5). SFG results provided molecular-level evidence for interfacial restructuring dynamics (Supplementary Fig. 6): nascent surfaces showed weak methyl signals (–CH₃ at 2875 cm⁻¹), suggesting disordered PEG chains configurations, whereas droplet motion-induced shear promoted chain alignment 30 , 31 , evidenced by intensified methyl signatures. Notably, conventional PEG-grafted LLS fabrication methods fail to achieve this transient superhydrophilicity. We attribute this phenomenon to: (1) centrifugation-induced PEG chains restructuring that preferentially exposes ether groups at the air/solid interface while sterically shielding methyl termini; and (2) stochastic distribution of non-covalently bounded PEG chains. Hydration-induced PEG swelling triggers the transition to a slippery state through conformational reorganization 32 – 36 , wherein water-mediated brush extension exposes methyl termini while shear forces promote their alignment into an ordered interfacial architecture 37 , 38 (Supplementary Fig. 7). The slippery surface obtained after water rinsing demonstrates exceptional stability, maintaining consistent contact angles and hysteresis with no significant degradation after 7 days under ambient conditions (20°C, 40% RH) or thermal aging (80°C) (Supplementary Fig. 8). Cyclic wettability switching of PEG-grafted LLS Prior to characterization, PEG-grafted LLS was rinsed (ethanol, 5min) to remove unbound chains, yielding the stable sliding state. Figure 1 a-d depict the operational cycle for achieving the wettability switching: liquid-mediated friction converts sliding to spreading state, while subsequent water rinsing regenerates the initial sliding state (Supplementary Movie 1). Since no chemical reactions are involved, we hypothesize that the aforementioned process is induced by conformational changes in PEG brushes. The abrupt decrease in the contact angle (33.2° to 4.1°) indicates substantial exposure of hydrophilic groups on the surface, suggesting a transition of the PEG brushes from an ordered state to a disordered state with exposed ether groups (Fig. 1 b, d). Subsequently, under uniform hydrodynamic shear forces, the molecular brush can undergo reordering and revert to an organized state. This switching behavior demonstrates broad applicability across PEG chain lengths (350-10000Da) and concentrations (0.05-20 mmol) (Fig. 1 e, f), and the universality is further supported by Fig. 1 g, showing identical switching in surfaces prepared via alternative methods, confirming it as an intrinsic property of PEG-grafted surfaces rather than preparation-dependent. Control experiments with PDMS maintained static wettability (Supplementary Fig. 9) under prolonged friction, validating that molecular wetting heterogeneity is essential for switching behavior. Significantly, the abovementioned switching process is reproducible for over 10 consecutive cycles without performance degradation (Supplementary Fig.10). SFG spectra revealed well-defined methyl (-CH 3 ) signatures at 2875cm − 1 (symmetric stretch), 2960cm − 1 (asymmetric stretch) and 2940cm − 1 (the Fermi resonance peak), indicating an ordered brush structure with interfacial methyl termination (Fig. 2 a). This configuration minimizes surface energy through preferential methyl group exposure 39 . Following wet friction treatment, the surface transitioned to a metastable spreading state. SFG spectra showed enhanced methylene (-CH 2 , symbol of ether groups) signals at 2845cm − 1 (symmetric stretch) and 2915 cm − 1 (asymmetric stretch), characteristic of disordered brush configurations with randomly oriented ether groups as the interface (Fig. 2 b). These results establish that the superhydrophilicity arises from methyl burial and ether groups exposure. Experiments with PEO 40 and hydroxyl-PEG-silane 20 grafted surfaces(almost the same WCA around 35°) confirm terminal groups contribute minimally to the change of WCA. Therefore, the effect preponderantly stems from brush conformational bending that maximizes interfacial exposure of hydratable ether groups. A closed switching cycle is achieved: water rinsing spontaneously reverts the spreading state to sliding state (Fig. 2 c; Supplementary Movie 1). Consistent with SFG data, surface roughness evolution correlates directly with brush disorder, where conformational randomization decreases topographical heterogeneity (Fig. 2 d-f, Supplementary Fig. 11). The spreading state is metastable and exhibits time-dependent wettability evolution, maintaining superhydrophilicity for at least 20 hours in ambient air (Supplementary Fig. 12) before thermodynamically driven methyl group re-exposure occurs (Supplementary Discussion 1). After 70 hours, the water contact angle recovered to 35° (comparable to the initial sliding state) but with elevated hysteresis (CAH = 12°), demonstrating that methyl reorientation alone cannot restore sliding state (Supplementary Fig. 13). Crucially, only external stimuli (e.g., water rinsing) can reorganize the disordered brushes into ordered configurations, restoring liquid-like property. This indicates that the essential coupling between solvation and mechanical forces in the switching mechanism. Mechanism of switchable wettability The wettability switching is predominantly mediated by wet friction, as evidenced by comparative experiments: dry friction (500 cycles) maintained relatively stable contact angles, whereas liquid environments induced complete state transitions within 20 hand-friction cycles (Fig. 3 a, test liquids: water, ethanol and cyclohexane). Notably, cyclohexane – a nonpolar solvent immiscible with water – also triggered wettability switching, confirming that the observed water droplet spreading is not an artifact of residual polar liquids(water/ethanol). Therefore, the wettability switching requires simultaneous solvent exposure and mechanical force application, indicating the solvation of PEG brushes serves as an activation threshold. Under dry friction conditions (despite ambient moisture absorption), the brushes maintain ordered methyl-terminated configurations stabilized by van der Waals interactions 41 . Applied shear/normal forces initially disorder the brush periphery (Fig. 3 b), creating a collapsed rigid layer that limits force propagation deeper into the brush matrix and prevents ether groups exposure. According to Fig. 3 d, dry friction induced a monotonic CAH increase to 12° after 500cycles of hand friction, reflecting liquid-like property loss from rigid barrier formation. Brush entanglement (Supplementary Fig. 14) restricted the chain mobility, impairing contact line accommodation. Water ultrasonication restored the CAH to 6°, demonstrating that dry friction primarily alters brush conformation without permanent damage. Load variation experiments (Fig. 3 e) showed excessive force prevents wettability switching and impairs CAH recovery, confirming that dry friction cannot drive the switching within the surface’s operational force limits. Mechanistically, without solvation, neither effective methyl burial nor ether groups exposure can occur during dry friction, precluding reversible switching. Solvation induces PEG brush swelling 18 : the brush thickness in spreading state exceeding that in sliding state by approximately 1.4 nm (12.9 ± 0.8 nm vs. 11.5 ± 0.7 nm, Supplementary Fig. 15), shifting dominant interactions from intermolecular van der Waals forces to brush-solvent interactions(for water and ethanol: hydrogen-bond). This enables force transmission throughout entire chain (Fig. 3 c), facilitating chain bending and ether groups exposure. However, the extended chain conformation increases steric hindrance (reducing conformational entropy) 42 , 43 , requiring applied forces to exceed a critical threshold for the switching. This explains why wet friction triggers the switching while the sliding state remains stable under ultrasonication(>12h, Fig. 3 f) as well as minimal friction fails to induce the switching (Supplementary Fig. 16) despite solvation effect exists in both conditions. Therefore, we developed a simplified mathematical model based on Alexander-de-Gennes theory 44 , 45 to calculate the critical external stress (shear) required for the wettability switching. The critical shear force \(\:{\tau\:}_{c}\) required for switching from sliding state to spreading should satisfy: $$\:{\tau\:}_{c}\ge\:{C}_{1}\text{sin}{\theta\:}_{c}\:+{C}_{2}\left(\frac{1}{\text{cos}{\theta\:}_{c}\text{sin}{\theta\:}_{c}\:}-\frac{1}{\text{sin}{\theta\:}_{c}\:}\right)+{C}_{3}\frac{1}{\text{sin}{\theta\:}_{c}\:}$$ where \(\:{\theta\:}_{c}\) represents the brush inclination angle relative to the surface normal in the spreading state. Full model derivation and parameter ( \(\:{C}_{i}\) ) values are provided in Supplementary Discussion 2. Steric constraints limit brush alignment to \(\:{\theta\:}_{c}=51.2^\circ\:\) (maximum achievable bending angle) in our model, preventing complete horizontal alignment ( \(\:{\theta\:}_{c}=90^\circ\:\) ). Besides, the spreading state becomes inaccessible at small \(\:{\theta\:}_{c}\) ,yielding impractical \(\:{\tau\:}_{c}\) values ( \(\:{\tau\:}_{c}\ge\:2*{10}^{4}\) kPa). Experimentally measured \(\:{\tau\:}_{c}\) values correspond to \(\:{\theta\:}_{c}=23^\circ\:\sim51.2^\circ\:\) , validating the model’s predictive range. Application of sliding state: dropwise condensation PEG-grafted LLS have been demonstrated to achieve a nearly 500% enhancement in heat transfer efficiency compared to hydrophobic dropwise condensation surfaces, owing to its ultrahigh nucleation rate and flattened droplet morphology 24 . We also found that the condensation properties differ drastically between the sliding and the spreading state. Figure 4 a shows simultaneous coexistence of both states on the adjacent regions of the same surface, and a clear contrast is observed: dropwise condensation dominates in the sliding zone(left), while the spreading region(right) favors filmwise condensation. This spatial decoupling of condensation modes (dropwise vs. filmwise) through molecular brush reorientation alone establishes a new paradigm for controlling phase-change heat transfer on chemically homogeneous surface. Besides, prolonged exposure(240s) to filmwise condensation failed to induce the spreading-to-sliding transition (Supplementary Fig. 17), experimentally aligning with our mechanistic analysis that the transition requires the synergistic action of shear forces and solvation effects, with mere solvation being insufficient. To demonstrate the superiority of PEG-grafted LLS’s condensation performance, we then compared the size distribution difference between the hydrophilic (PEG-grafted) and hydrophobic LLSs (PDMS-grafted). Under steady-state conditions, they both exhibited similar droplet distribution conforming to the Rose-distribution 24 . Furthermore, our findings reveal a pronounced condensation divergence between PEG-grafted and PDMS-grafted surface following droplet coalescence: PEG-grafted surface exhibit immediate re-nucleation on freshly exposed areas, while PDMS-grafted surface shows significant nucleation hysteresis (Fig. 4 b, d). Though ultra-low CAH(<5°) enhances droplet coalescence, direct visualization reveals a greater nucleation rate and suggests the superior heat transfer and water harvesting potential of the PEG-grafted LLS. Figure 4 f displays temporal evolution of droplet size distribution on PEG and PDMS surfaces. Both surfaces exhibit asymptotic decay distributions where small droplets (<50 µm) dominate numerically while large droplets remain scarce, with stable proportional trends. Remarkably, the PEG surface achieves dual-phase enhancement compared to hydrophobic surfaces: 1) higher population density of condensed droplets 2) a greater proportion of ultra-small(<10um) droplets in its size distribution, combing with its outstanding defrosting performance(Supplementary Fig. 18), showing exceptional potential as a cost-effective alternative to expensive hydrophobic modification methods for heat exchangers 20 . Application of spreading state: oil-repellency underwater The PEG-grafted LLS is amphiphilic (Supplementary Scheme. 1, Supplementary Fig. 19) in both sliding and spreading state. As demonstrated by Kota et al. 25 , 26 , it has stronger affinity for water than oil in air in sliding state as the water droplet will penetrate the oil film and then come in contact with the surface (Supplementary Fig. 20). We therefore evaluated the underwater oil-repellency of both states. Remarkably, spreading-state surface spontaneously detach oil(100µL) droplets underwater within 0.8s, even in dry state, while the sliding-state surface merely induce droplet contraction (hemispherical shape) without detachment (Fig. 5 a), and this divergence stems from state-dependent hydration capabilities 46 , 47 . As analyzed before, surface in sliding state exhibits methyl-terminated brush orientation with minimal ether group exposure, whereas the spreading state maximizes it (Supplementary Fig. 21). The SFG signals reveals pronounced signals at 3250 cm − 1 (strong hydrogen-bond) and 3450 cm − 1 (weak hydrogen-bond) 48 exclusively in the spreading state, confirming its superior hydration capability (Fig. 5 b). This enables unprecedented oil detachment kinetics(<2s for 10–120 µL droplets in dry conditions, Supplementary Fig. 22), outperforming conventional sulfonic acid based superhydrophilic coatings 49 (5-12s detachment, Fig. 4 c) and reported materials (Supplementary Table 1). While sulfonate groups typically dominate interfacial hydration design 50 , 51 , the PEG surface in spreading state exhibits superior oil-repellency despite lacking strong dipoles-suggesting a new approach to oil-resistant surfaces via hydration-optimized polymer brushes. Force analysis at the oil droplet’s three-phase contact line during detachment reveals that the upmost oil-repellency of PEG-grafted LLS in spreading state origins from the high hydration capacity enabled by three-dimensionally close-packed ether groups and the low sliding resistance resulting from the flexible brushes. $$\:{\varvec{F}}_{\varvec{d}\varvec{r}\varvec{i}\varvec{v}\varvec{e}}={\varvec{F}}_{\varvec{h}\varvec{y}\varvec{d}\varvec{r}\varvec{a}\varvec{t}\varvec{i}\varvec{o}\varvec{n}}-{\varvec{F}}_{\varvec{f}\varvec{r}\varvec{i}\varvec{c}\varvec{t}\varvec{i}\varvec{o}\varvec{n}}-{\varvec{F}}_{\varvec{s}\varvec{u}\varvec{r}\varvec{f}\varvec{a}\varvec{c}\varvec{e}}$$ The higher \(\:{F}_{hydration}\) together with lower \(\:{F}_{friction}\) contributes a higher \(\:{F}_{drive}\) , thus bringing outstanding oil resistance under water (Supplementary Discussion 3, Fig. 5 d). Besides the superfast detaching velocity, the spreading state demonstrates both universal oil-repellency(Supplementary Fig.23) and robust stability(maintain <1s detachment through ≥8 cycles and 15-85 ℃ temperature variations; Fig. 5 e, f). Therefore, PEG-grafted LLS in spreading state exhibiting both strong hydration capability and low detaching resistance can provide guidance for designing next-generation high-efficiency oil-repellent surfaces. Conclusion In conclusion, hydrophilic LLSs have demonstrated many unique properties with broad application potential distinct from the extensively studied omniphobic LLSs. As a key material for fabricating such surfaces, polyethylene glycol (PEG) has been widely utilized in biomedical and chemical engineering fields, yet some of its unique physicochemical properties still require further exploration. In our study, we reveal a novel mechanism for regulating surface wettability through molecular conformation transition of PEG-grafted LLS. Three fundamental breakthroughs have been achieved: First, reversible wettability switching has been discovered to be mediated by solvent-assisted conformational transitions of PEG brushes, enabling cyclic switching between droplet spreading (contact angle ≈ 4°) and sliding (contact angle ≈ 35°) states through simple wet friction/water rinsing. Second, a novel condensation modulation paradigm has been established, allowing the simultaneous coexistence of dropwise and filmwise condensation on chemically homogeneous surfaces through local brush reorientation. Third, a design strategy for developing next-generation oil-repellent surfaces is proposed, our analysis displays that the ultra-fast oil detaching performance (< 0.8 s) of PEG-grafted LLS stems from the synergistic combination of hydration capability and surface smoothness. Key mechanistic insights from SFG spectroscopy demonstrate that external shear forces under solvation induce PEG chains' bending, triggering interfacial transition from methyl-terminated ordered arrays to ether group-enriched disordered configurations. The technological implications extend beyond fundamental surface science, offering new insights for: 1) Smart thermal management systems with spatially programmable condensation modes, 2) High-efficiency anti-oil fouling coatings, and 3) Wettability-switchable platforms for microfluidics. However, challenges remain in achieving long-term stability, particularly concerning the stabilization of the metastable spreading state and the development of oxidation-resistant alternatives to PEG. References Chen L, Huang S, Ras RHA, Tian X (2023) Omniphobic liquid-like surfaces. 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Supplementary Files SupplementaryMovie2oilrepellencyunderwaterinspreadingstate.mov Underwater oil repellency of PEG-grafted LLS in spreading state SupplementaryMovie3detachinghexadecane.mov Detaching hexadecane SupplementaryMovie1wettabilityswitchingphenomenon.mov Reversible wettability switching phenomenon SupplementaryMovie4dropletsliding.mov Droplet sliding SupplementaryInformation.docx Hydrophilic PEG-grafted liquid-like surface: sliding or spreading Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIiWNgGAWjYDAC5gNsIEoOwmMjRgtbAliZMelaEhuI1mJwjP3Zg587atPnt/cYMHwoO8zAP7uBkBaGdMPeM8dzN5w5Y8A449xhBok7Bwhoud9wTIK37VjuBokcA2betsMMBhIJhGxhbJP823YsXX7+GwPmv8RpYWaT5m2rSWC4wWPAzEiMFsljbGzSsm0HDDecSSs42HMunUfiBgEtfMAQk3zbVicv335444MfZdZy/DMIaFE4AKYOg0kQmwe/eiCQbwBTdQQVjoJRMApGwQgGAEvfRCczticqAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-3225-5502","institution":"Southeast University","correspondingAuthor":true,"prefix":"","firstName":"Youfa","middleName":"","lastName":"zhang","suffix":""},{"id":469240959,"identity":"23f7d4c3-80f4-47ea-b0c8-52582a1d64a4","order_by":1,"name":"Junxu Chen","email":"","orcid":"","institution":"Southeast University","correspondingAuthor":false,"prefix":"","firstName":"Junxu","middleName":"","lastName":"Chen","suffix":""},{"id":469240960,"identity":"4d32042b-3af8-450d-972f-a69e36cac3bc","order_by":2,"name":"Pengfei Zhang","email":"","orcid":"","institution":"Southeast University","correspondingAuthor":false,"prefix":"","firstName":"Pengfei","middleName":"","lastName":"Zhang","suffix":""},{"id":469240961,"identity":"1e14f3b8-0a25-4f30-847c-6219c7a4855e","order_by":3,"name":"Wei Wang","email":"","orcid":"","institution":"Nanjing Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Wang","suffix":""},{"id":469240962,"identity":"ef7d2c6d-0b99-4c0a-87af-1af30c8a2fe2","order_by":4,"name":"Weilin Deng","email":"","orcid":"","institution":"Xinjiang University","correspondingAuthor":false,"prefix":"","firstName":"Weilin","middleName":"","lastName":"Deng","suffix":""},{"id":469240963,"identity":"1d27caf7-b4d5-4bf6-b5dd-8d3d401daf9b","order_by":5,"name":"Xinquan Yu","email":"","orcid":"","institution":"Southeast University","correspondingAuthor":false,"prefix":"","firstName":"Xinquan","middleName":"","lastName":"Yu","suffix":""},{"id":469240964,"identity":"ec6331a3-adb6-4494-ae22-519d9a70b7e3","order_by":6,"name":"Xiaofeng Han","email":"","orcid":"","institution":"Southeast University","correspondingAuthor":false,"prefix":"","firstName":"Xiaofeng","middleName":"","lastName":"Han","suffix":""}],"badges":[],"createdAt":"2025-06-06 08:05:55","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6834931/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6834931/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84867539,"identity":"5474e730-26ce-417f-ba77-fb22a5a241b3","added_by":"auto","created_at":"2025-06-18 08:33:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":190918,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eWettability switching behavior of PEG-grafted LLS. a, b \u003c/strong\u003eOptic images of droplet movement on surface in sliding and spreading state. \u003cstrong\u003ec, d, \u003c/strong\u003eIllustration of conformational changes of the PEG brushes during wettability switching and the WCA of the sliding and spreading state. \u003cstrong\u003ee, f, g, \u003c/strong\u003ePEG-grafted surfaces with varying chain length(e), concentrations(f), and alternative preparation methods(g) all showing the wettability switching behavior.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/64f2a47046a83337e21b6545.png"},{"id":84867538,"identity":"7d25c928-daed-436b-8bb2-10b961e40694","added_by":"auto","created_at":"2025-06-18 08:33:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":271591,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSFG signals difference of methyl and methylene groups and the change of surface roughness in each state. a, d, \u003c/strong\u003eBefore wet friction (sliding state),\u003cstrong\u003e b, e, \u003c/strong\u003eAfter wet friction (spreading state) and \u003cstrong\u003ec, f, \u003c/strong\u003eAfter water rinsing (sliding state).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/bac155fe7ea010413edaf8f4.png"},{"id":84867189,"identity":"410a5d2c-fb7a-42bd-98e3-247116d4b8b1","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":164862,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eWettability switching mechanism: conjecture, evidence, and model. a, \u003c/strong\u003eThe change of WCA during the dry friction and wet friction.\u003cstrong\u003e b, \u003c/strong\u003eRigid barrier formation during dry friction, preventing conformational changes. \u003cstrong\u003ec, \u003c/strong\u003eSolvation-induced brush extension during wet friction, enabling force transmission and chain orientation.\u003cstrong\u003e d, \u003c/strong\u003eCAH and SA changes during dry friction\u003cstrong\u003e. e, \u003c/strong\u003eLoad-dependent CAH evolution showing irreversible changes at high forces.\u003cstrong\u003e f, \u003c/strong\u003eStability of the sliding state under 12h ethanol ultrasonication.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/866d64b3b83e9bb3e1dfc809.png"},{"id":84867194,"identity":"4ea83dad-b6d4-4ebc-bbcf-b4ec65dd9006","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":754481,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison of condensation characteristics. a, \u003c/strong\u003eSpatially decoupled condensation modes on PEG-grafted surface: dropwise condensation in sliding state(left) versus filmwise condensation in the spreading state(right).\u003cstrong\u003e b, c, d, e, \u003c/strong\u003eCondensation morphology comparison. Optical (b, c) and microscopic (d, e) photographs of condensation on the PEG-grafted (b, d) and PDMS-grafted surfaces (c, e).\u003cstrong\u003e f, \u003c/strong\u003eDroplet size distribution analysis of PEG-grafted and PDMS-grafted surfaces during the condensation.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/0fc63b5882f8fc4e992925de.png"},{"id":84867540,"identity":"f9cc05af-834c-480c-ba27-af960a59a82d","added_by":"auto","created_at":"2025-06-18 08:33:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":299695,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOil detaching performance of the PEG-grafted surface at spreading state.\u003c/strong\u003e \u003cstrong\u003e​a​\u003c/strong\u003e​, Spreading state enables ultrafast oil detachment (0.8 s) versus adhesive sliding state (\u0026gt;20 s retention). \u003cstrong\u003eb​\u003c/strong\u003e​, SFG spectra contrast showing enhanced hydrogen-bonded water signals (3250/3450 cm⁻¹) in spreading state. \u003cstrong\u003ec​\u003c/strong\u003e​, Superior dry-state performance to sulfonic-rich coatings (1 s vs 5–12 s detachment). \u003cstrong\u003ed​\u003c/strong\u003e​, Analysis of the principle of rapid oil detachment. \u003cstrong\u003ee\u003c/strong\u003e,\u003cstrong\u003e f​\u003c/strong\u003e​, Robust stability demonstrated through (e) ≥8 switching cycles and (f) 15–85°C operation.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/03860946ae1864b6106f974a.png"},{"id":84868705,"identity":"f45426ff-2e68-46dd-b0a0-73c9f3813582","added_by":"auto","created_at":"2025-06-18 08:41:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2193954,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/e45e1b11-e4f1-4844-b32c-d225dabeaf43.pdf"},{"id":84867188,"identity":"f8f7281c-c3a6-40dc-b469-8bfd2132c65c","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"mov","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1804869,"visible":true,"origin":"","legend":"Underwater oil repellency of PEG-grafted LLS in spreading state","description":"","filename":"SupplementaryMovie2oilrepellencyunderwaterinspreadingstate.mov","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/83de1f6f1a0591e7e28aa948.mov"},{"id":84867192,"identity":"480c618e-1c03-4d00-b4c3-b601f62c2ec2","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"mov","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":8668405,"visible":true,"origin":"","legend":"Detaching hexadecane","description":"","filename":"SupplementaryMovie3detachinghexadecane.mov","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/a92284a172b46558b00db9c5.mov"},{"id":84867198,"identity":"ba7ff280-6f1c-486d-88f4-1c10f82a430f","added_by":"auto","created_at":"2025-06-18 08:25:23","extension":"mov","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":66769260,"visible":true,"origin":"","legend":"\u003cp\u003eReversible wettability switching phenomenon\u003c/p\u003e","description":"","filename":"SupplementaryMovie1wettabilityswitchingphenomenon.mov","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/b3e10c1de49496d65b03da88.mov"},{"id":84867196,"identity":"491bf97f-9222-4cef-9032-c8117b29e988","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"mov","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":3137575,"visible":true,"origin":"","legend":"Droplet sliding","description":"","filename":"SupplementaryMovie4dropletsliding.mov","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/5d61f8a8c10375167315cb85.mov"},{"id":84867195,"identity":"5955fee3-1d37-4fc9-95d4-c23634500a74","added_by":"auto","created_at":"2025-06-18 08:25:22","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":5240017,"visible":true,"origin":"","legend":"Hydrophilic PEG-grafted liquid-like surface: sliding or spreading","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6834931/v1/eaef7bbe4ebe5ad6647afab8.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Hydrophilic PEG-grafted liquid-like surface: sliding or spreading","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLiquid-like surfaces (LLSs), an emerging frontier in surface/interface science\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, have garnered increasing attention owing to their exceptional liquid repellency, which does not rely on fragile texture\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e or low-retention lubricant\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Recent advances have focused primarily on omniphobic LLSs fabricated from materials such as polydimethylsiloxane(PDMS)\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, perfluoropolyether(PFPE)\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e and flexible alkyl chains\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, with applications spanning anti-fouling\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, anti-scaling\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e, droplet transport\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e and oil-water separation\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. However, hydrophilic LLSs remain understudied despite their significant potential.\u003c/p\u003e \u003cp\u003eIn contrast to omniphobic LLSs, hydrophilic LLSs exhibits counterintuitive wetting behavior, characterized by the coexistence of static hydrophilicity and dynamic hydrophobicity. The predominant approach of fabricating such LLSs in current literature involves the covalent immobilization of poly(ethylene glycol)(PEG) chains, typically methoxy-PEG-silane (mPEG-silane), to silica surfaces\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. The inherent hydrophilicity of PEG-grafted LLSs originates from ether(-O-) groups in the polymer backbone, which enable strong hydration via hydrogen bonding with water molecules\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Moreover, the synergistic effect of flexible ether groups and terminal methoxy groups reduces the energy barrier for water droplet three-phase contact line motion, enabling ultralow contact angle hysteresis(CAH) \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. In 2001, Papra et al.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e first demonstrated ultrathin mPEG-silane-grafted surfaces with CAH below 3\u0026deg;. Following a nearly 20-year gap, Hozumi et al.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e revitalized PEG-grafted LLS research by developing an innovative PEG-TEOS hybrid film that exhibiting CAH below 5\u0026deg; and good defrosting ability which potentially addresses the water-bridge effect in radiators. Whether the role of TEOS is as a binder or a nano-spacer\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e and the origin of the paradoxical wettability\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e have likewise been investigated by them. Intriguingly, these systems can achieve near-superhydrophilicity and suppress the coffee-ring effect upon alkaline treatment\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Further unprecedented observations include the dropwise condensation capability of PEG-grafted LLSs which exhibit superior heat transfer efficiency compared to conventional hydrophobic LLSs\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, as well as anti-biofouling performance arising from PEG\u0026rsquo;s combined slipperiness and hydrophilicity\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. These findings underscore the untapped potential of PEG-grafted LLSs, warranting deeper investigation into their latent functionalities.\u003c/p\u003e \u003cp\u003eBuilding on the intrinsic heterogeneous wettability of PEG chains\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, we demonstrate that PEG-grafted LLS exhibits reversible wettability switching between water droplet sliding and spreading under wet friction and water rinsing(Supplementary Scheme. 1). The Sum frequency generation (SFG) spectroscopy results show that the switching mechanism is mediated by the conformation changes of PEG chains by external forces. Beyond a critical shear force, conformational bending sterically occludes terminal methyl groups while exposes the ether groups, inducing surface reconstruction that promotes droplet spreading. In the absence of solvent plasticization, a mechanically rigid barrier forms that decouples applied shear forces from the chains, suppressing conformational switching. This regime only enhances droplet adhesion during droplet motion without substantially modifying the surface free energy (contact angle). Based on this unique wetting property, reversible switching between dropwise and filmwise condensation on material surfaces can be achieved solely by modulating the conformation of polymer brushes. Remarkably, for the first time we discovered that the densely packed ether groups endows the surface with robust hydration capability\u003csup\u003e\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e, the reoriented PEG brushes (at spreading state) exhibited spontaneous oil detachment within 0.8s \u0026ndash; this exceptional oil-repellency underwater suggests a new paradigm for designing high-performance anti-oilfouling surfaces.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eWettability switching phenomena\u003c/h2\u003e \u003cp\u003eThe fabrication of PEG-grafted LLS was accomplished via spin-coating deposition of mPEG-silane (Supplementary Fig.\u0026nbsp;1) ethanolic dispersions onto oxygen plasma-treated silica substrates, following a standardized protocol\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. The observed C-O peak shift was consistent with established silanization mechanisms\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e(Supplementary Fig.\u0026nbsp;2). Systematic screening across PEG molecular weights (350\u0026ndash;2000 Da) and concentrations (0.05\u0026ndash;20 mM) revealed negligible CAH variations (Supplementary Fig.\u0026nbsp;3). The 750 Da mPEG-silane (9\u0026ndash;12 ethylene oxide units) with 1mM concentration exhibited optimal performance, with minimal CAH (Δθ\u0026thinsp;=\u0026thinsp;3.2\u0026deg;) and maximal droplet mobility ( \u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.77 mm/s, 10 \u0026micro;L with tilting 5\u0026deg;), and was therefore selected for further characterization (Supplementary Fig.\u0026nbsp;4).\u003c/p\u003e \u003cp\u003eUnlike previously reported toluene-based immersion methods\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e or tetraethyl orthosilicate (TEOS) crosslinking approaches\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, the ethanol-assisted spin-coating technique produced an initially superhydrophilic surface (water contact angle\u0026thinsp;=\u0026thinsp;3.1\u0026deg; in freshly prepared samples, defined as the \u003cb\u003espreading state\u003c/b\u003e). This state displayed metastability, undergoing rapid transition to a slippery state upon exposure to water droplet rinsing, which hereafter is designated as the \u003cb\u003esliding state\u003c/b\u003e (Supplementary Fig.\u0026nbsp;5).\u003c/p\u003e \u003cp\u003eSFG results provided molecular-level evidence for interfacial restructuring dynamics (Supplementary Fig.\u0026nbsp;6): nascent surfaces showed weak methyl signals (\u0026ndash;CH₃ at 2875 cm⁻\u0026sup1;), suggesting disordered PEG chains configurations, whereas droplet motion-induced shear promoted chain alignment\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e, evidenced by intensified methyl signatures. Notably, conventional PEG-grafted LLS fabrication methods fail to achieve this transient superhydrophilicity. We attribute this phenomenon to: (1) centrifugation-induced PEG chains restructuring that preferentially exposes ether groups at the air/solid interface while sterically shielding methyl termini; and (2) stochastic distribution of non-covalently bounded PEG chains. Hydration-induced PEG swelling triggers the transition to a slippery state through conformational reorganization\u003csup\u003e\u003cspan additionalcitationids=\"CR33 CR34 CR35\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e, wherein water-mediated brush extension exposes methyl termini while shear forces promote their alignment into an ordered interfacial architecture\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e (Supplementary Fig.\u0026nbsp;7).\u003c/p\u003e \u003cp\u003eThe slippery surface obtained after water rinsing demonstrates exceptional stability, maintaining consistent contact angles and hysteresis with no significant degradation after 7 days under ambient conditions (20\u0026deg;C, 40% RH) or thermal aging (80\u0026deg;C) (Supplementary Fig.\u0026nbsp;8).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCyclic wettability switching of PEG-grafted LLS\u003c/h3\u003e\n\u003cp\u003ePrior to characterization, PEG-grafted LLS was rinsed (ethanol, 5min) to remove unbound chains, yielding the stable sliding state. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-d depict the operational cycle for achieving the wettability switching: liquid-mediated friction converts sliding to spreading state, while subsequent water rinsing regenerates the initial sliding state (Supplementary Movie 1). Since no chemical reactions are involved, we hypothesize that the aforementioned process is induced by conformational changes in PEG brushes. The abrupt decrease in the contact angle (33.2\u0026deg; to 4.1\u0026deg;) indicates substantial exposure of hydrophilic groups on the surface, suggesting a transition of the PEG brushes from an ordered state to a disordered state with exposed ether groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, d). Subsequently, under uniform hydrodynamic shear forces, the molecular brush can undergo reordering and revert to an organized state.\u003c/p\u003e \u003cp\u003eThis switching behavior demonstrates broad applicability across PEG chain lengths (350-10000Da) and concentrations (0.05-20 mmol) (Fig. \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee, f), and the universality is further supported by Fig. \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg, showing identical switching in surfaces prepared via alternative methods, confirming it as an intrinsic property of PEG-grafted surfaces rather than preparation-dependent. Control experiments with PDMS maintained static wettability (Supplementary Fig. 9) under prolonged friction, validating that molecular wetting heterogeneity is essential for switching behavior. Significantly, the abovementioned switching process is reproducible for over 10 consecutive cycles without performance degradation (Supplementary Fig.10).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSFG spectra revealed well-defined methyl (-CH\u003csub\u003e3\u003c/sub\u003e) signatures at 2875cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (symmetric stretch), 2960cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(asymmetric stretch) and 2940cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(the Fermi resonance peak), indicating an ordered brush structure with interfacial methyl termination (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). This configuration minimizes surface energy through preferential methyl group exposure\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. Following wet friction treatment, the surface transitioned to a metastable spreading state. SFG spectra showed enhanced methylene (-CH\u003csub\u003e2\u003c/sub\u003e, symbol of ether groups) signals at 2845cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(symmetric stretch) and 2915 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (asymmetric stretch), characteristic of disordered brush configurations with randomly oriented ether groups as the interface (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). These results establish that the superhydrophilicity arises from methyl burial and ether groups exposure. Experiments with PEO\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e and hydroxyl-PEG-silane\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e grafted surfaces(almost the same WCA around 35\u0026deg;) confirm terminal groups contribute minimally to the change of WCA. Therefore, the effect preponderantly stems from brush conformational bending that maximizes interfacial exposure of hydratable ether groups. A closed switching cycle is achieved: water rinsing spontaneously reverts the spreading state to sliding state (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec; Supplementary Movie 1). Consistent with SFG data, surface roughness evolution correlates directly with brush disorder, where conformational randomization decreases topographical heterogeneity (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed-f, Supplementary Fig.\u0026nbsp;11).\u003c/p\u003e \u003cp\u003eThe spreading state is metastable and exhibits time-dependent wettability evolution, maintaining superhydrophilicity for at least 20 hours in ambient air (Supplementary Fig.\u0026nbsp;12) before thermodynamically driven methyl group re-exposure occurs (Supplementary Discussion 1). After 70 hours, the water contact angle recovered to 35\u0026deg; (comparable to the initial sliding state) but with elevated hysteresis (CAH\u0026thinsp;=\u0026thinsp;12\u0026deg;), demonstrating that methyl reorientation alone cannot restore sliding state (Supplementary Fig.\u0026nbsp;13). Crucially, only external stimuli (e.g., water rinsing) can reorganize the disordered brushes into ordered configurations, restoring liquid-like property. This indicates that the essential coupling between solvation and mechanical forces in the switching mechanism.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eMechanism of switchable wettability\u003c/h3\u003e\n\u003cp\u003eThe wettability switching is predominantly mediated by wet friction, as evidenced by comparative experiments: dry friction (500 cycles) maintained relatively stable contact angles, whereas liquid environments induced complete state transitions within 20 hand-friction cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, test liquids: water, ethanol and cyclohexane). Notably, cyclohexane \u0026ndash; a nonpolar solvent immiscible with water \u0026ndash; also triggered wettability switching, confirming that the observed water droplet spreading is not an artifact of residual polar liquids(water/ethanol). Therefore, the wettability switching requires simultaneous solvent exposure and mechanical force application, indicating the solvation of PEG brushes serves as an activation threshold. Under dry friction conditions (despite ambient moisture absorption), the brushes maintain ordered methyl-terminated configurations stabilized by van der Waals interactions\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Applied shear/normal forces initially disorder the brush periphery (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), creating a collapsed rigid layer that limits force propagation deeper into the brush matrix and prevents ether groups exposure.\u003c/p\u003e \u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, dry friction induced a monotonic CAH increase to 12\u0026deg; after 500cycles of hand friction, reflecting liquid-like property loss from rigid barrier formation. Brush entanglement (Supplementary Fig.\u0026nbsp;14) restricted the chain mobility, impairing contact line accommodation. Water ultrasonication restored the CAH to 6\u0026deg;, demonstrating that dry friction primarily alters brush conformation without permanent damage. Load variation experiments (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee) showed excessive force prevents wettability switching and impairs CAH recovery, confirming that dry friction cannot drive the switching within the surface\u0026rsquo;s operational force limits. Mechanistically, without solvation, neither effective methyl burial nor ether groups exposure can occur during dry friction, precluding reversible switching.\u003c/p\u003e \u003cp\u003eSolvation induces PEG brush swelling\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e: the brush thickness in spreading state exceeding that in sliding state by approximately 1.4 nm (12.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8 nm vs. 11.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7 nm, Supplementary Fig.\u0026nbsp;15), shifting dominant interactions from intermolecular van der Waals forces to brush-solvent interactions(for water and ethanol: hydrogen-bond). This enables force transmission throughout entire chain (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec), facilitating chain bending and ether groups exposure. However, the extended chain conformation increases steric hindrance (reducing conformational entropy)\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e, requiring applied forces to exceed a critical threshold for the switching. This explains why wet friction triggers the switching while the sliding state remains stable under ultrasonication(\u0026gt;12h, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef) as well as minimal friction fails to induce the switching (Supplementary Fig.\u0026nbsp;16) despite solvation effect exists in both conditions. Therefore, we developed a simplified mathematical model based on Alexander-de-Gennes theory\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e to calculate the critical external stress (shear) required for the wettability switching.\u003c/p\u003e \u003cp\u003eThe critical shear force \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e required for switching from sliding state to spreading should satisfy:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\tau\\:}_{c}\\ge\\:{C}_{1}\\text{sin}{\\theta\\:}_{c}\\:+{C}_{2}\\left(\\frac{1}{\\text{cos}{\\theta\\:}_{c}\\text{sin}{\\theta\\:}_{c}\\:}-\\frac{1}{\\text{sin}{\\theta\\:}_{c}\\:}\\right)+{C}_{3}\\frac{1}{\\text{sin}{\\theta\\:}_{c}\\:}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\theta\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e represents the brush inclination angle relative to the surface normal in the spreading state. Full model derivation and parameter (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{C}_{i}\\)\u003c/span\u003e\u003c/span\u003e) values are provided in Supplementary Discussion 2.\u003c/p\u003e \u003cp\u003eSteric constraints limit brush alignment to \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\theta\\:}_{c}=51.2^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e (maximum achievable bending angle) in our model, preventing complete horizontal alignment (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\theta\\:}_{c}=90^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e). Besides, the spreading state becomes inaccessible at small \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\theta\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e ,yielding impractical \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e values (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{c}\\ge\\:2*{10}^{4}\\)\u003c/span\u003e\u003c/span\u003e kPa). Experimentally measured \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e values correspond to \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\theta\\:}_{c}=23^\\circ\\:\\sim51.2^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e, validating the model\u0026rsquo;s predictive range.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eApplication of sliding state: dropwise condensation\u003c/h3\u003e\n\u003cp\u003ePEG-grafted LLS have been demonstrated to achieve a nearly 500% enhancement in heat transfer efficiency compared to hydrophobic dropwise condensation surfaces, owing to its ultrahigh nucleation rate and flattened droplet morphology\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. We also found that the condensation properties differ drastically between the sliding and the spreading state. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea shows simultaneous coexistence of both states on the adjacent regions of the same surface, and a clear contrast is observed: dropwise condensation dominates in the sliding zone(left), while the spreading region(right) favors filmwise condensation. This spatial decoupling of condensation modes (dropwise vs. filmwise) through molecular brush reorientation alone establishes a new paradigm for controlling phase-change heat transfer on chemically homogeneous surface. Besides, prolonged exposure(240s) to filmwise condensation failed to induce the spreading-to-sliding transition (Supplementary Fig.\u0026nbsp;17), experimentally aligning with our mechanistic analysis that the transition requires the synergistic action of shear forces and solvation effects, with mere solvation being insufficient.\u003c/p\u003e \u003cp\u003eTo demonstrate the superiority of PEG-grafted LLS\u0026rsquo;s condensation performance, we then compared the size distribution difference between the hydrophilic (PEG-grafted) and hydrophobic LLSs (PDMS-grafted). Under steady-state conditions, they both exhibited similar droplet distribution conforming to the Rose-distribution\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Furthermore, our findings reveal a pronounced condensation divergence between PEG-grafted and PDMS-grafted surface following droplet coalescence: PEG-grafted surface exhibit immediate re-nucleation on freshly exposed areas, while PDMS-grafted surface shows significant nucleation hysteresis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, d). Though ultra-low CAH(\u0026lt;5\u0026deg;) enhances droplet coalescence, direct visualization reveals a greater nucleation rate and suggests the superior heat transfer and water harvesting potential of the PEG-grafted LLS. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef displays temporal evolution of droplet size distribution on PEG and PDMS surfaces. Both surfaces exhibit asymptotic decay distributions where small droplets (\u0026lt;50 \u0026micro;m) dominate numerically while large droplets remain scarce, with stable proportional trends. Remarkably, the PEG surface achieves dual-phase enhancement compared to hydrophobic surfaces: 1) higher population density of condensed droplets 2) a greater proportion of ultra-small(\u0026lt;10um) droplets in its size distribution, combing with its outstanding defrosting performance(Supplementary Fig.\u0026nbsp;18), showing exceptional potential as a cost-effective alternative to expensive hydrophobic modification methods for heat exchangers\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eApplication of spreading state: oil-repellency underwater\u003c/h3\u003e\n\u003cp\u003eThe PEG-grafted LLS is amphiphilic (Supplementary Scheme. 1, Supplementary Fig.\u0026nbsp;19) in both sliding and spreading state. As demonstrated by Kota et al.\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, it has stronger affinity for water than oil in air in sliding state as the water droplet will penetrate the oil film and then come in contact with the surface (Supplementary Fig.\u0026nbsp;20). We therefore evaluated the underwater oil-repellency of both states.\u003c/p\u003e \u003cp\u003eRemarkably, spreading-state surface spontaneously detach oil(100\u0026micro;L) droplets underwater within 0.8s, even in dry state, while the sliding-state surface merely induce droplet contraction (hemispherical shape) without detachment (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea), and this divergence stems from state-dependent hydration capabilities\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. As analyzed before, surface in sliding state exhibits methyl-terminated brush orientation with minimal ether group exposure, whereas the spreading state maximizes it (Supplementary Fig.\u0026nbsp;21). The SFG signals reveals pronounced signals at 3250 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (strong hydrogen-bond) and 3450 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(weak hydrogen-bond)\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e exclusively in the spreading state, confirming its superior hydration capability (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). This enables unprecedented oil detachment kinetics(\u0026lt;2s for 10\u0026ndash;120 \u0026micro;L droplets in dry conditions, Supplementary Fig.\u0026nbsp;22), outperforming conventional sulfonic acid based superhydrophilic coatings\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e (5-12s detachment, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) and reported materials (Supplementary Table\u0026nbsp;1). While sulfonate groups typically dominate interfacial hydration design\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e,\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e, the PEG surface in spreading state exhibits superior oil-repellency despite lacking strong dipoles-suggesting a new approach to oil-resistant surfaces via hydration-optimized polymer brushes.\u003c/p\u003e \u003cp\u003eForce analysis at the oil droplet\u0026rsquo;s three-phase contact line during detachment reveals that the upmost oil-repellency of PEG-grafted LLS in spreading state origins from the high hydration capacity enabled by three-dimensionally close-packed ether groups and the low sliding resistance resulting from the flexible brushes.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{\\varvec{F}}_{\\varvec{d}\\varvec{r}\\varvec{i}\\varvec{v}\\varvec{e}}={\\varvec{F}}_{\\varvec{h}\\varvec{y}\\varvec{d}\\varvec{r}\\varvec{a}\\varvec{t}\\varvec{i}\\varvec{o}\\varvec{n}}-{\\varvec{F}}_{\\varvec{f}\\varvec{r}\\varvec{i}\\varvec{c}\\varvec{t}\\varvec{i}\\varvec{o}\\varvec{n}}-{\\varvec{F}}_{\\varvec{s}\\varvec{u}\\varvec{r}\\varvec{f}\\varvec{a}\\varvec{c}\\varvec{e}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe higher \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{F}_{hydration}\\)\u003c/span\u003e\u003c/span\u003e together with lower \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{F}_{friction}\\)\u003c/span\u003e\u003c/span\u003e contributes a higher \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{F}_{drive}\\)\u003c/span\u003e\u003c/span\u003e, thus bringing outstanding oil resistance under water (Supplementary Discussion 3, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBesides the superfast detaching velocity, the spreading state demonstrates both universal oil-repellency(Supplementary Fig.23) and robust stability(maintain \u0026lt;1s detachment through \u0026ge;8 cycles and 15-85 ℃ temperature variations; Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee, f). Therefore, PEG-grafted LLS in spreading state exhibiting both strong hydration capability and low detaching resistance can provide guidance for designing next-generation high-efficiency oil-repellent surfaces.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, hydrophilic LLSs have demonstrated many unique properties with broad application potential distinct from the extensively studied omniphobic LLSs. As a key material for fabricating such surfaces, polyethylene glycol (PEG) has been widely utilized in biomedical and chemical engineering fields, yet some of its unique physicochemical properties still require further exploration. In our study, we reveal a novel mechanism for regulating surface wettability through molecular conformation transition of PEG-grafted LLS. Three fundamental breakthroughs have been achieved: First, reversible wettability switching has been discovered to be mediated by solvent-assisted conformational transitions of PEG brushes, enabling cyclic switching between droplet spreading (contact angle\u0026thinsp;\u0026asymp;\u0026thinsp;4\u0026deg;) and sliding (contact angle\u0026thinsp;\u0026asymp;\u0026thinsp;35\u0026deg;) states through simple wet friction/water rinsing. Second, a novel condensation modulation paradigm has been established, allowing the simultaneous coexistence of dropwise and filmwise condensation on chemically homogeneous surfaces through local brush reorientation. Third, a design strategy for developing next-generation oil-repellent surfaces is proposed, our analysis displays that the ultra-fast oil detaching performance (\u0026lt;\u0026thinsp;0.8 s) of PEG-grafted LLS stems from the synergistic combination of hydration capability and surface smoothness.\u003c/p\u003e \u003cp\u003eKey mechanistic insights from SFG spectroscopy demonstrate that external shear forces under solvation induce PEG chains' bending, triggering interfacial transition from methyl-terminated ordered arrays to ether group-enriched disordered configurations. The technological implications extend beyond fundamental surface science, offering new insights for: 1) Smart thermal management systems with spatially programmable condensation modes, 2) High-efficiency anti-oil fouling coatings, and 3) Wettability-switchable platforms for microfluidics. However, challenges remain in achieving long-term stability, particularly concerning the stabilization of the metastable spreading state and the development of oxidation-resistant alternatives to PEG.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen L, Huang S, Ras RHA, Tian X (2023) Omniphobic liquid-like surfaces. Nat Rev Chem 7:123\u0026ndash;137\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheng X, Zhao R, Wang S, Meng J (2024) Liquid-Like Surfaces with Enhanced De-Wettability and Durability: From Structural Designs to Potential Applications. Adv Mater 36:2407315\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang S, Liu K, Yao X, Jiang L (2015) Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications. 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Angew Chem Int Ed 59:14466\u0026ndash;14472\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6834931/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6834931/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eStudy on counterintuitive hydrophilic liquid-like surface (LLS) remain in a nascent stage despite its exceptional application potential in interfacial engineering. Here, inspired by the inherent wetting heterogeneity of mPEG-silane, for the first time we discover a dynamic wettability switching mechanism in PEG-grafted LLS through solvation-coupled mechanical regulation of PEG brush conformations. Ordered methoxy-terminated brushes enable water droplet sliding (θ\u0026thinsp;\u0026asymp;\u0026thinsp;33\u0026deg;), while disordered ether-exposed configurations induce spreading (θ\u0026thinsp;\u0026asymp;\u0026thinsp;4\u0026deg;). This conformational control allows unprecedented spatial decoupling of condensation modes (dropwise vs filmwise) on homogeneous surfaces, with sliding-state LLS showing increase nucleation efficiency versus PDMS-grafted LLS. Notably, spreading-state surface achieves ultrafast underwater oil detachment (\u0026lt;\u0026thinsp;0.8 s) through synergistic hydration from dense ether groups and low friction from flexible brushes. Our findings establish molecular conformation engineering as a paradigm for designing multifunctional LLS with applications spanning smart thermal management, microfluidic systems, and novel anti-oil fouling coatings.\u003c/p\u003e","manuscriptTitle":"Hydrophilic PEG-grafted liquid-like surface: sliding or spreading","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-18 08:25:17","doi":"10.21203/rs.3.rs-6834931/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2cd2620b-b88c-4dc7-91da-4fcfb41c30cc","owner":[],"postedDate":"June 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":49820020,"name":"Physical sciences/Chemistry/Materials chemistry/Soft materials/Polymers"},{"id":49820021,"name":"Physical sciences/Chemistry/Materials chemistry/Soft materials/Wetting"},{"id":49820022,"name":"Physical sciences/Chemistry/Materials chemistry/Soft materials/Self-assembly"}],"tags":[],"updatedAt":"2025-06-18T08:25:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-18 08:25:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6834931","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6834931","identity":"rs-6834931","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}