Terahertz absorption characteristics of guar gum determined via microfluidic technology

Terahertz absorption characteristics of guar gum determined via microfluidic technology | 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 Research Terahertz absorption characteristics of guar gum determined via microfluidic technology Fengxuan Zhang, Guoyang Wang, Haiyun Huang, Menghan Chen, Sijia Zhang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-302211/v2 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Aug, 2021 Read the published version in Journal of the European Optical Society-Rapid Publications → Version 2 posted 15 You are reading this latest preprint version Show more versions Abstract The vibrational energy levels of many biomolecules correspond to the terahertz band; thus, terahertz technology can be used to identify these substances. Moreover, as the biological activity of most biomolecules can be observed only in aqueous solution, the characteristics of such biomolecules must be studied in aqueous solution. In this study, a simple microfluidic chip, a temperature control device and a strong electric field device were designed to study the terahertz absorption characteristics of guar gum for different temperatures, concentrations and electric field exposure durations, thus enabling the use of terahertz technology to analyse the characteristics of guar gum. Materials Chemistry Terahertz Guar gum Microfluidic chip Temperature Concentration Electric field Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Electromagnetic waves in the terahertz (THz) band have a frequency range of 0.1–10 THz and a wavelength range of 0.03–3 mm. Studies have shown that the characteristic vibration modes of many biological macromolecules correspond to the THz band [1]; consequently, THz waves can be used to detect biological molecules [2-6]. Water plays an important role in the function of biomolecules, and thus, most experiments are performed in the solution state. Interactions among hydrated molecules in solution involve multiple biological phenomena [7], which are often denoted as hydration. Based on this principle, Yang et al. measured the spectrum of L-asparagine and L-asparagine monohydrate via THz time domain spectroscopy (THz-TDS) technology. In addition, he also observed dynamic changes in L-asparagine thermal dehydration in real time and found that THz waves are highly sensitive to changes in the crystal structure, the condition of the solution in which the crystal is contained and weak interactions between molecules [8]. Microfluidics, also known as lab-on-a-chip or microfluidic chip technology, enable researchers to precisely control and manipulate micro-scale fluids with submicron structures. Thus, microfluidics have practical value for distinguishing similar substances and detecting trace samples. Fisher et al. [9] measured the optical constants of four nucleotides in the THz band using THz technology and successfully identified these nucleotides. Serita et al. developed a THz microfluidic chip based on a nonlinear optical crystal, comprising an array of several split ring resonators, for the detection of ultra-trace biological samples [10] Baragwanath et al. used THz-TDS to examine a microfluidic chip and found that the time domain spectrum, refractive index and other parameters differed greatly for different concentrations and substances [11]. Thus, THz spectroscopy technology is a powerful tool for distinguishing substances and studying their structures. Guar gum is an emulsifier, curing agent and stabiliser. Guam gum can act as a thickening liquid, can increase viscosity and reduce ice crystal formation, and is used in most processed foods. In this study, THz technology and microfluidic approaches were combined to study the THz absorption characteristics of guar gum for different concentrations, temperatures and electric field treatment durations. The method presented herein provides a feasible approach for rapidly identifying colloids. Properties of guar gum The molecular structure of guar gum is shown in Fig. 1 [12]. Guar gum is extracted from the endosperm of the leguminous plant guar bean as a free-flowing powder. The powder is generally white to light yellowish brown in colour and is nearly odourless. Guar gum is composed of approximately 75%–85% polysaccharide, 5%–6% protein, 2%–3% fibre and 1% ash. Guar gum is a non-ionic neutral polysaccharide, with D-mannose linked by a β-1,4 bond as the main chain and D-galactose linked at the α-1,6 position as the branch chain. In general, the molar ratio of galactose to mannose is 1:2. The spatial structure of the plant is a curled spherical structure, with mannose on the inside and galactose on the outside. The ratio of mannose to galactose varies slightly for different plant varieties. Guar gum [12] is a type of water-soluble natural polymer, which can be quickly hydrated in cold or hot water to obtain a translucent viscous liquid. The viscosity of a guar-gum-containing aqueous solution reflects the molecular weight of guar gum, while the swelling rate reflects the degree of difficulty that is encountered in swelling in guar gum applications. Higher temperatures can accelerate the swelling of guar gum, weaken the hydrogen bonding between molecular chains, increase the elongation of molecular chains and reduce the viscosity. Notably, guar gum can form a high-viscosity aqueous solution at low concentrations [12] due to entanglement between polymer chains and intramolecular and intermolecular hydrogen bonding. The viscosity of 1% guar gum in aqueous solution is approximately 4000–6000 MPa∙s. In addition, guar gum aqueous solutions exhibit typical winding polymer characteristics, corresponding to the pseudoplastic fluid characteristics of a non-Newtonian fluid, with no yield stress. Because guar gum is widely utilized and exhibits a high viscosity and rheological properties in natural rubber, the THz absorption of guar gum was studied in this work, with guar gum acting as a representative colloid for further experimental research. Experimental system Experimental light path An in-house-built THz-TDS system was employed in this work. The light source is a self-mode-locked fibre femtosecond laser purchased from Peking University, with a central wavelength of 1550 nm, pulse width of 75 fs, pulse repetition rate of 100 MHz and power of 130mW. After passing through a polarising beam splitter prism, the output laser is divided into two beams. One beam is used as the pump light, which is coupled into a fibre-optic photoconductive antenna (BPCA-100-05-10-1550-c-f, BATOP Company) through a mechanical translation stage to generate a THz wave. The other beam is used as a detection beam, which is coupled into another fibre-optic photoconductive antenna (BPCA-180-05-10-1550-c-f of BATOP Company) to detect THz waves. The fabricated microfluidic chip is placed between two off-axis parabolic mirrors. The THz wave emitted by the THz antenna passes through the microfluidic chip filled with guar gum, is received by the detection antenna and is then input into the lock-in amplifier for amplification. Next, the data are collected and processed by a computer. A schematic of the experimental optical path is shown in Fig. 2. Fabrication of the microfluidic chip THz microfluidic chip materials should exhibit high transmittance and allow for ease in processing. Currently, microfluidic chips are generally made of quartz glass, polydimethylsiloxane (PDMS) or polyethylene (PE). However, due to the low transmittance of quartz glass and PDMS for THz waves and the opacity of PE to visible light, these materials do not allow one to observe changes in liquid samples in a channel in real time. The transmittance of the cycloolefin copolymer Zeonor 1420R used in this study exceeds 90% and displays no obvious peaks, as shown in Fig. 3, which is suitable for the preparation of THz microfluidic chips. The microfluidic chip in this study is a sandwich structure, with a 50-μm-thick strongly adhering double-sided adhesive as an interlayer and a concave microfluidic channel carved in the middle. The substrate and cover are composed of Zeonor 1420R material. A diagram of the process for preparing the microfluidic chip is shown in Fig. 4. In this study, we first measured the THz transmission characteristics of the microfluidic chip during continuous heating without liquid injection in order to assess the THz transmission characteristics of the chip under varying temperature. The results show that the transmission characteristics of the chip are not affected by temperature and that there is no leakage phenomenon. Therefore, the chip is suitable for the detection of liquid samples at different temperatures. Temperature control system To control the temperature of the guar gum, a high-precision temperature control system was designed. First, the fabricated microfluidic chip was bonded to a 2-mm-thick iron sheet by using a thermal conductive silica gel. A 6-mm-diameter hole was created on the iron sheet for THz waves to pass through. Second, a temperature sensor was secured to the same side of the iron sheet using thermal conductive silica gel. A circular alumina ceramic heating plate with holes (outer diameter: 40 mm; inner diameter: 10 mm) was glued to the other side of the iron sheet using thermal conductive silica gel in order to heat the microfluidic chip. The heating plate and temperature sensor were controlled by a temperature controller (ST700 intelligent PID temperature controller; temperature adjustment range: 0–400 °C; rated voltage: 220 V; working frequency: 50–60 Hz). The temperature controller, which is shown in Fig. 5, can adjust the temperature with an accuracy of 0.1 °C. External electric field device A schematic diagram of the external electric field device utilised in this experiment is shown in Fig. 6. A high-voltage power supply (dw-p153-05c51) was used to provide power. A uniform electric field was generated by two parallel metal plates, with a magnitude of approximately 2500 V/cm. The microfluidic chip was placed between the two metal plates for electric field treatment; subsequently, the two metal plates were removed, and the transmission of the microfluidic chip was measured by the THz-TDS system. Experiments And Results Temperature characteristics In this experiment, guar gum was prepared by adding 0.01 g guar gum powder to 500 mL deionised water; then, the mixture was stirred evenly and heated in a water bath for 2 min, resulting in 0.002% guar gum solution. When the colloid was irradiated with a laser pen, an obvious Tyndall effect was observed, indicating that the solution was a sol. The microfluidic chip was filled with the guar gum solution and placed between off-axis parabolic mirrors to conduct a transmission test using the THz-TDS system. The transmittance at room temperature (25 °C) was measured first, followed by the transmittance at 30 °C to 70 °C, measured in increments of 10 °C. When the temperature reaches 60 °C, the colloid inside the chip produces bubbles due to the temperature rise, and the measured signal fluctuates. To reduce the influence of bubbles on the measured signal, guar gum solution was continuously injected into the microfluidic chip when bubbles occurred during the heating process, and the solution was injected until the bubbles in the chip were eliminated. In this process, the colloid in the chip heats rapidly. When the guar gum solution reaches the target temperature, there are fewer bubbles in the water, which will not affect the analysis of the measured data. The THz time domain spectrum of guar gum is shown in Fig. 7, and the spectrum obtained by Fourier transform spectroscopy is shown in Fig. 8. The results shown in these figures demonstrate that the THz transmission intensity of guar gum decreases with increasing temperature, indicating that the THz absorption of guar gum increases with increasing temperature in the range of 25 °C–70 °C. Concentration characteristics Three concentrations of guar gum solution (0.1%, 0.3% and 0.4%) were prepared with deionised water. The THz frequency spectra for these solutions are shown in Fig. 9. These results indicate that a higher concentration of guar gum solution corresponds to a lower THz transmission intensity, resulting in a stronger THz absorption. Characteristics under an applied electric field The 0.002% guar gum solution was injected into the microfluidic chip, and the THz spectrum was obtained via the THz-TDS system without an electric field. Then, an electric field of 2500V/cm was applied parallel to the microfluidic chip, and the guar gum solution was placed in the electric field for 5 min. The power supply was then disconnected, the electrode plate was removed, and the THz spectrum was obtained with the THz-TDS system. Next, the microfluidic chip was shaken to return the sample to the original state as much as possible, the sample was placed in the electric field for 10 min, and the THz spectrum was obtained again. The THz spectra obtained in these three measurements are shown in Fig. 10. The results show that the THz transmittance increases with an increasing duration of electric field exposure, implying that the THz absorption intensity of the guar gum solution decreases. Discussion The THz spectra of guar gum solution at varying temperatures show that the THz transmittance decreases with increasing temperature. This result occurs because the outer layer of hydroxyl, alkoxy and oxygen atoms in glycoside bonds in guar gum molecules containing sp 3 hybrid orbitals. The unshared lone electron pairs in the orbitals can combine with partially positively charged hydrogen in the water molecule to form hydrogen bonds through electrostatic attraction [13]. Due to the stretching of guar gum molecules, a variety of groups are fully exposed. The polar groups and polar water molecules interact with each other by hydrogen bonding or dipole forces to form an inner-layer water film. The inner-layer water reacts with the outer-layer water to form an association. The sol molecules with a large volume act as the skeleton, a large amount of water is bound, and free movement of the medium is hindered, resulting in resistance between laminar flows. This resistance is exhibited as apparent viscosity, which causes the solution to display a quantitative viscosity [14]. When the temperature rises, the rate of molecular motion gradually increases, and the aggregates change from large to small. With an increase in absorbed energy, the structure of the system breaks down, and the viscosity decreases. In this process, the oxidative degradation of guar gum molecules leads to hydrogen bond breaking [14], and the THz transmission intensity should be enhanced. However, guar gum solution is a polar liquid in which dipole interactions occur. The absorption coefficient of polar liquids is larger in the THz range approximately 10–100 times that of non-polar liquids [15]. Therefore, the vibration between dipole molecules is the main reason that the THz absorption of guar gum increases with increasing temperature. The THz transmission spectra of guar gum solution for varying concentrations (Fig. 9) show that the transmission intensity of THz waves decreases with increasing concentration; consequently, the THz absorption of guar gum solution increases. This result is due to the existence of hydrogen bonds between the guar gum molecules. An increase in the guar gum concentration leads to a higher number of hydrogen bonds, which in turn increases the absorption of THz waves. In addition, the vibration interactions between dipole molecules in the polar guar gum liquid also contribute to the increased THz absorption [15]. The THz transmission spectra of guar gum solution exposed to an electric field for varying durations (Fig. 10) indicate that a longer exposure to an electric field results in a higher THz transmission intensity for guar gum solution. This result occurs because the applied electric field can reduce hydrogen bonding and increase the diffusion coefficient of water molecules [16]. Therefore, it can be preliminarily concluded that the external electric field reduces the effect of hydrogen bonds in the sample, which increases the THz transmission; thus, the THz absorption intensity decreases as the duration of external electric field exposure increases. Conclusion In this paper, a new method for fabricating a THz microfluidic chip is proposed. A double-sided adhesive was used as the channel interlayer of the microfluidic chip, which greatly shortens the fabrication time and resolves the issue of chip leakage. A high-precision temperature control system was designed to control the temperature of guar gum solution, and a high-voltage power supply was used to provide a strong electric field. The THz transmission characteristics of guar gum solution were measured for different temperatures, concentrations and electric field exposure durations via a THz-TDS system, which indirectly reflected the THz absorption characteristics of guar gum. The results show that the transmission intensity of THz waves in guar gum solution decreases with increasing temperature and concentration. This phenomenon was attributed to the viscosity of guar gum, the number of hydrogen bonds in solution and the vibration of dipole molecules. In addition, as the duration of electric field exposure increased, the THz transmittance of the guar gum solution increased, which was attributed to hydrogen bonds. This study expands the potential applications for THz technology and lays a foundation for the study of colloidal properties using THz methods. Abbreviations PBS: polarisation beam splitter; PCA: Photoconductive Antenna; PID: Proportion Integration Differentiation. Declarations Acknowledgment The authors would like to thank ‘enago’ for providing English touch up. Authors’ contributions All authors contributed to the theoretical analysis, calculations, experiment and preparation of the manuscript. Funding This work was supported by the National Natural Science Foundation of China under Grant No. 61575131. Availability of data and materials Information about data was detailed in the article. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Author details 1 Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing 100048, China . 2 Beijing Key Laboratory of Terahertz Spectroscopy and Imaging, Beijing 100048, China . 3 Beijing Advanced Innovation Center for Imaging Theory and Technology, Beijing 100048, China . 4 Department of Physics, Capital Normal University, Beijing 100048, China. References Gu,H., Shi,C., Wu,X., Peng,Y.: Molecular methylation detection based on terahertz metamaterial technology . Analyst. 145 (20), 6705-6712 (2020) Zhou,R., Wang,C., Xu,W., Xie,L.: Biological applications of terahertz technology based on nanomaterials and nanostructures. Nanoscale. 11(8), 3445-3457 (2019) Ma,Y., Huang,H., Hao,S., Qiu,K., Zheng,Z.: Insights into the water status in hydrous minerals using terahertz time-domain spectroscopy. Sci. Rep. 9 (1), 9265 (2019) Gallerano,G., Doria,A., Giovenale,E.: Photopolymer fiber fiber based on fiber fiber fiber. J. Opt. 4 (1), 17-24 (2014) Bennett,D., Taylor,Z.,Tewari,P., Sung,S., Maccabi,A., Singh,R.: Assessment of Corneal Hydration in the Terahertz band. J. Bio. Opt. 17 (9), 097008 (2012) Shiraga,K., Ogawa,Y., Kondo,N., Irisawa,A., Imamura,M.: Hydration of saccharides via attenuated terahertz temporal-domain reflection spectroscopy. Food Chem. 140 (2) , 315 (2013) Duponchel,L., Laurette,S., Hatirnaz,B., Treizebre,A., Affouard,F., Bocquet,B.: Terahertz microfluidic sensor for in situ exploration of hydration shell of molecules. Chemometr Intell LAB. 123 28-35 (2013) Yang,J., Li,S., Zhao,H., Zhang,J., Yang,N., Jing,D., Wang,C., Han,J.: Terahertz spectroscopy of L-asparagine and its monohydrate. Acta Physica Sinica. 63 (13) 105-111 (2014) Fischer,B., Walther,M., Jepsen,P.: Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy. Phys. Med. Biol. 47 (21), 3807 (2002) Serita,K., Tonouchi,M.: A Terahertz Microfluidic Chip for Ultra-trace Biosensing.Nippon Laser Igakkaishi. 39(4), 329-334 (2019) Baragwanath,A., Swift,G., Dai,D., Gallant,A., Chamberlain,J.: Silicon based microfluidic cell for terahertz frequencies. Jpn J Appl Phys. 108(1) 013102-013102-8 (2010) Wang,X.: Preparation of Modified Guar Gum and Its Application in Reactive Dye Printing of Cotton Fabrics. Zhejiang Sci-Tech University (2017) Xie,J., Liu,S., Gu,Z.: Study on factors affecting the rheological properties of guar gum. Guangzhou Food Industry Science and Technology. 1007-2764 (2004) Wu,X.: Preparation of Guar gum modified adhesive and its application in textile field. Suzhou University(2018) Son,J.: Terahertz Biomedical Science and Technology. CRC Press. 347-350 (2014) Yang,Z., Chai,Z., Zhang,H.: Effect of electric field on water diffusion on kaolinite surface. Meitan Xuebao. 11(2020) Cite Share Download PDF Status: Published Journal Publication published 11 Aug, 2021 Read the published version in Journal of the European Optical Society-Rapid Publications → Version 2 posted Editorial decision: Major revision 19 May, 2021 Review # 4 received at journal 18 May, 2021 Review # 2 received at journal 07 May, 2021 Review # 3 received at journal 03 May, 2021 Reviewer # 4 agreed at journal 20 Apr, 2021 Reviewer # 3 agreed at journal 19 Apr, 2021 Review # 1 received at journal 19 Apr, 2021 Reviewer # 2 agreed at journal 18 Apr, 2021 Reviews received at journal 18 Apr, 2021 Reviewers invited by journal 18 Apr, 2021 Reviewer # 1 agreed at journal 18 Apr, 2021 Editor invited by journal 15 Apr, 2021 Editor assigned by journal 14 Apr, 2021 Submission checks completed at journal 14 Apr, 2021 First submitted to journal 08 Mar, 2021 You are reading this latest preprint version Show more versions 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-302211","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research","associatedPublications":[],"authors":[{"id":22114978,"identity":"6e93ea88-c6b5-41bc-a59d-a827afd6f113","order_by":0,"name":"Fengxuan Zhang","email":"","orcid":"https://orcid.org/0000-0003-3968-0800","institution":"Capital Normal University","correspondingAuthor":false,"prefix":"","firstName":"Fengxuan","middleName":"","lastName":"Zhang","suffix":""},{"id":22114979,"identity":"4afc6f66-4564-42f7-b2f9-7fd51bbe2b7e","order_by":1,"name":"Guoyang Wang","email":"","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":false,"prefix":"","firstName":"Guoyang","middleName":"","lastName":"Wang","suffix":""},{"id":22114980,"identity":"cbc63376-e480-4178-8d4d-ea783819e12c","order_by":2,"name":"Haiyun Huang","email":"","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":false,"prefix":"","firstName":"Haiyun","middleName":"","lastName":"Huang","suffix":""},{"id":22114981,"identity":"375a0c24-2c1a-4cab-ad70-4efecca5f9ab","order_by":3,"name":"Menghan Chen","email":"","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":false,"prefix":"","firstName":"Menghan","middleName":"","lastName":"Chen","suffix":""},{"id":22114982,"identity":"1c0b9028-d58a-4863-9766-ddda5fc35e5f","order_by":4,"name":"Sijia Zhang","email":"","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":false,"prefix":"","firstName":"Sijia","middleName":"","lastName":"Zhang","suffix":""},{"id":22114983,"identity":"4db69383-36f1-42de-87d6-de4ed1bab185","order_by":5,"name":"Bo Su","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIiWNgGAWjYFACHgbmv39sYGwitTDwNqSRruUwCVrkZ+QefCC547y8uUQC44O3bQzy5oS0GNzISzYwPHPbcOeMBGbDuW0MhjsbCGmRyDGTSGC7nWBwI4FNmreNIcHgAEGHAbUcYDsH0sL+mygtDDdyzCQb2w6AbWEmSovBmXfJxgxnkg03nHnYLDnnnIThBoIOa889+Jihwk7e4HjywQ9vymzkCTsMARgbgIQE8epHwSgYBaNgFOAGAOYMPc2gniwRAAAAAElFTkSuQmCC","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":true,"prefix":"","firstName":"Bo","middleName":"","lastName":"Su","suffix":""},{"id":22114984,"identity":"fd86948a-8d24-455b-b6f6-b3dcf83e58d9","order_by":6,"name":"Cunlin Zhang","email":"","orcid":"","institution":"Capital Normal University Department of Physics","correspondingAuthor":false,"prefix":"","firstName":"Cunlin","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2021-03-06 10:29:05","currentVersionCode":2,"declarations":"","doi":"10.21203/rs.3.rs-302211/v2","doiUrl":"https://doi.org/10.21203/rs.3.rs-302211/v2","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s41476-021-00162-x","type":"published","date":"2021-08-11T15:01:20+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":8181238,"identity":"d6645196-77c7-4034-b6df-0353eb1a8aef","added_by":"auto","created_at":"2021-04-19 19:27:38","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":31882,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/0e67732b781ad58efa619c95.jpg"},{"id":8180821,"identity":"c9d8b151-8f99-4e1d-8dfd-d0969b08beae","added_by":"auto","created_at":"2021-04-19 19:21:38","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":27930,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/53d42319dd064bef4d069f4a.jpg"},{"id":8180673,"identity":"72899423-d3aa-4490-953e-4fcbdac9cd41","added_by":"auto","created_at":"2021-04-19 19:18:38","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":29275,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/89232febaee560a72dfc6e94.jpg"},{"id":8180820,"identity":"fac900b3-42c0-4c67-85c8-d602bf75262e","added_by":"auto","created_at":"2021-04-19 19:21:38","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":20671,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/045dfd8461f7c641322c06da.jpg"},{"id":8180841,"identity":"635c3659-aef9-42eb-afe0-c1caa687421f","added_by":"auto","created_at":"2021-04-19 19:21:46","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":25577,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/6573690224f9f75ab250a528.jpg"},{"id":8180825,"identity":"7cade70f-3f15-4df3-a0e5-121bd67e1f5d","added_by":"auto","created_at":"2021-04-19 19:21:38","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":25876,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/15e502f080d906bf77611ba7.jpg"},{"id":8180899,"identity":"550f3aaa-5adc-4516-98b0-0f038cae6000","added_by":"auto","created_at":"2021-04-19 19:24:38","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":38752,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/179d839f3bdcc8b2725a0263.jpg"},{"id":8180680,"identity":"54f19b0d-d1e0-44c3-bee2-773ac565fe87","added_by":"auto","created_at":"2021-04-19 19:18:38","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":39248,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/ea8c9dedb3f3798f9868ed88.jpg"},{"id":8180676,"identity":"5d4a1781-e8e3-4f85-b2b8-c6d0bcc1705a","added_by":"auto","created_at":"2021-04-19 19:18:38","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":32945,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/8df6b3418c5cd928bce7873a.jpg"},{"id":8181929,"identity":"ee26f356-c4c7-4f2e-b68e-ddb535fa432f","added_by":"auto","created_at":"2021-04-19 19:30:38","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":34725,"visible":true,"origin":"","legend":"(see figure file for caption) ","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/6ac55ca01d8ea70cb8c4e6bf.jpg"},{"id":13687211,"identity":"67319be7-7d8b-4e93-98b7-db901c172e2b","added_by":"auto","created_at":"2021-09-17 12:18:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":475337,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-302211/v2/ea9351e2-e325-4a45-970d-0f66a0530ad3.pdf"}],"financialInterests":"","formattedTitle":"Terahertz absorption characteristics of guar gum determined via microfluidic technology","fulltext":[{"header":"Introduction","content":"\u003cp\u003eElectromagnetic waves in the terahertz (THz) band have a frequency range of 0.1\u0026ndash;10 THz and a wavelength range of 0.03\u0026ndash;3 mm. Studies have shown that the characteristic vibration modes of many biological macromolecules correspond to the THz band [1]; consequently, THz waves can be used to detect biological molecules [2-6]. Water plays an important role in the function of biomolecules, and thus, most experiments are performed in the solution state. Interactions among hydrated molecules in solution involve multiple biological phenomena [7], which are often denoted as hydration. Based on this principle, Yang et al. measured the spectrum of L-asparagine and L-asparagine monohydrate via THz time domain spectroscopy (THz-TDS) technology. In addition, he also observed dynamic changes in L-asparagine thermal dehydration in real time and found that THz waves are highly sensitive to changes in the crystal structure, the condition of the solution in which the crystal is contained and weak interactions between molecules [8]. Microfluidics, also known as lab-on-a-chip or microfluidic chip technology, enable researchers to precisely control and manipulate micro-scale fluids with submicron structures. Thus, microfluidics have practical value for distinguishing similar substances and detecting trace samples. Fisher et al. [9] measured the optical constants of four nucleotides in the THz band using THz technology and successfully identified these nucleotides. Serita et al. developed a THz microfluidic chip based on a nonlinear optical crystal, comprising an array of several split ring resonators, for the detection of ultra-trace biological samples [10] Baragwanath et al. used THz-TDS to examine a microfluidic chip and found that the time domain spectrum, refractive index and other parameters differed greatly for different concentrations and substances [11]. Thus, THz spectroscopy technology is a powerful tool for distinguishing substances and studying their structures.\u003c/p\u003e\n\u003cp\u003eGuar gum is an emulsifier, curing agent and stabiliser. Guam gum can act as a thickening liquid, can increase viscosity and reduce ice crystal formation, and is used in most processed foods. In this study, THz technology and microfluidic approaches were combined to study the THz absorption characteristics of guar gum for different concentrations, temperatures and electric field treatment durations. The method presented herein provides a feasible approach for rapidly identifying colloids.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eProperties of guar gum\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe molecular structure of guar gum is shown in Fig. 1 [12]. Guar gum is extracted from the endosperm of the leguminous plant guar bean as a free-flowing powder. The powder is generally white to light yellowish brown in colour and is nearly odourless. Guar gum is composed of approximately 75%\u0026ndash;85% polysaccharide, 5%\u0026ndash;6% protein, 2%\u0026ndash;3% fibre and 1% ash.\u003c/p\u003e\n\u003cp\u003eGuar gum is a non-ionic neutral polysaccharide, with D-mannose linked by a \u0026beta;-1,4 bond as the main chain and D-galactose linked at the \u0026alpha;-1,6 position as the branch chain. In general, the molar ratio of galactose to mannose is 1:2. The spatial structure of the plant is a curled spherical structure, with mannose on the inside and galactose on the outside. The ratio of mannose to galactose varies slightly for different plant varieties.\u003c/p\u003e\n\u003cp\u003eGuar gum [12] is a type of water-soluble natural polymer, which can be quickly hydrated in cold or hot water to obtain a translucent viscous liquid. The viscosity of a guar-gum-containing aqueous solution reflects the molecular weight of guar gum, while the swelling rate reflects the degree of difficulty that is encountered in swelling in guar gum applications. Higher temperatures can accelerate the swelling of guar gum, weaken the hydrogen bonding between molecular chains, increase the elongation of molecular chains and reduce the viscosity.\u003c/p\u003e\n\u003cp\u003eNotably, guar gum can form a high-viscosity aqueous solution at low concentrations [12] due to entanglement between polymer chains and intramolecular and intermolecular hydrogen bonding. The viscosity of 1% guar gum in aqueous solution is approximately 4000\u0026ndash;6000 MPa∙s. In addition, guar gum aqueous solutions exhibit typical winding polymer characteristics, corresponding to the pseudoplastic fluid characteristics of a non-Newtonian fluid, with no yield stress. Because guar gum is widely utilized and exhibits a high viscosity and rheological properties in natural rubber, the THz absorption of guar gum was studied in this work, with guar gum acting as a representative colloid for further experimental research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExperimental system\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExperimental light path\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn in-house-built THz-TDS system was employed in this work. The light source is a self-mode-locked fibre femtosecond laser purchased from Peking University, with a central wavelength of 1550 nm, pulse width of 75 fs, pulse repetition rate of 100 MHz and power of 130mW. After passing through a polarising beam splitter prism, the output laser is divided into two beams. One beam is used as the pump light, which is coupled into a fibre-optic photoconductive antenna (BPCA-100-05-10-1550-c-f, BATOP Company) through a mechanical translation stage to generate a THz wave. The other beam is used as a detection beam, which is coupled into another fibre-optic photoconductive antenna (BPCA-180-05-10-1550-c-f of BATOP Company) to detect THz waves. The fabricated microfluidic chip is placed between two off-axis parabolic mirrors. The THz wave emitted by the THz antenna passes through the microfluidic chip filled with guar gum, is received by the detection antenna and is then input into the lock-in amplifier for amplification. Next, the data are collected and processed by a computer. A schematic of the experimental optical path is shown in Fig. 2.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFabrication of \u003c/strong\u003e\u003cstrong\u003ethe \u003c/strong\u003e\u003cstrong\u003emicrofluidic chip\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTHz microfluidic chip materials should exhibit high transmittance and allow for ease in processing. Currently, microfluidic chips are generally made of quartz glass, polydimethylsiloxane (PDMS) or polyethylene (PE). However, due to the low transmittance of quartz glass and PDMS for THz waves and the opacity of PE to visible light, these materials do not allow one to observe changes in liquid samples in a channel in real time. The transmittance of the cycloolefin copolymer Zeonor 1420R used in this study exceeds 90% and displays no obvious peaks, as shown in Fig. 3, which is suitable for the preparation of THz microfluidic chips.\u003c/p\u003e\n\u003cp\u003eThe microfluidic chip in this study is a sandwich structure, with a 50-\u0026mu;m-thick strongly adhering double-sided adhesive as an interlayer and a concave microfluidic channel carved in the middle. The substrate and cover are composed of Zeonor 1420R material. A diagram of the process for preparing the microfluidic chip is shown in Fig. 4. In this study, we first measured the THz transmission characteristics of the microfluidic chip during continuous heating without liquid injection in order to assess the THz transmission characteristics of the chip under varying temperature. The results show that the transmission characteristics of the chip are not affected by temperature and that there is no leakage phenomenon. Therefore, the chip is suitable for the detection of liquid samples at different temperatures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTemperature control system\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo control the temperature of the guar gum, a high-precision temperature control system was designed. First, the fabricated microfluidic chip was bonded to a 2-mm-thick iron sheet by using a thermal conductive silica gel. A 6-mm-diameter hole was created on the iron sheet for THz waves to pass through. Second, a temperature sensor was secured to the same side of the iron sheet using thermal conductive silica gel. A circular alumina ceramic heating plate with holes (outer diameter: 40 mm; inner diameter: 10 mm) was glued to the other side of the iron sheet using thermal conductive silica gel in order to heat the microfluidic chip. The heating plate and temperature sensor were controlled by a temperature controller (ST700 intelligent PID temperature controller; temperature adjustment range: 0\u0026ndash;400 \u0026deg;C; rated voltage: 220 V; working frequency: 50\u0026ndash;60 Hz). The temperature controller, which is shown in Fig. 5, can adjust the temperature with an accuracy of 0.1 \u0026deg;C.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExternal electric field device\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA schematic diagram of the external electric field device utilised in this experiment is shown in Fig. 6. A high-voltage power supply (dw-p153-05c51) was used to provide power. A uniform electric field was generated by two parallel metal plates, with a magnitude of approximately 2500 V/cm. The microfluidic chip was placed between the two metal plates for electric field treatment; subsequently, the two metal plates were removed, and the transmission of the microfluidic chip was measured by the THz-TDS system.\u003c/p\u003e"},{"header":"Experiments And Results","content":"\u003cp\u003e\u003cstrong\u003eTemperature characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this experiment, guar gum was prepared by adding 0.01 g guar gum powder to 500 mL deionised water; then, the mixture was stirred evenly and heated in a water bath for 2 min, resulting in 0.002% guar gum solution. When the colloid was irradiated with a laser pen, an obvious Tyndall effect was observed, indicating that the solution was a sol. The microfluidic chip was filled with the guar gum solution and placed between off-axis parabolic mirrors to conduct a transmission test using the THz-TDS system. The transmittance at room temperature (25 \u0026deg;C) was measured first, followed by the transmittance at 30 \u0026deg;C to 70 \u0026deg;C, measured in increments of 10 \u0026deg;C. When the temperature reaches 60 \u0026deg;C, the colloid inside the chip produces bubbles due to the temperature rise, and the measured signal fluctuates. To reduce the influence of bubbles on the measured signal, guar gum solution was continuously injected into the microfluidic chip when bubbles occurred during the heating process, and the solution was injected until the bubbles in the chip were eliminated. In this process, the colloid in the chip heats rapidly. When the guar gum solution reaches the target temperature, there are fewer bubbles in the water, which will not affect the analysis of the measured data. The THz time domain spectrum of guar gum is shown in Fig. 7, and the spectrum obtained by Fourier transform spectroscopy is shown in Fig. 8. The results shown in these figures demonstrate that the THz transmission intensity of guar gum decreases with increasing temperature, indicating that the THz absorption of guar gum increases with increasing temperature in the range of 25 \u0026deg;C\u0026ndash;70 \u0026deg;C.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConcentration characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree concentrations of guar gum solution (0.1%, 0.3% and 0.4%) were prepared with deionised water. The THz frequency spectra for these solutions are shown in Fig. 9. These results indicate that a higher concentration of guar gum solution corresponds to a lower THz transmission intensity, resulting in a stronger THz absorption.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacteristics \u003c/strong\u003e\u003cstrong\u003eunder an\u003c/strong\u003e\u003cstrong\u003e applied electric field\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe 0.002% guar gum solution was injected into the microfluidic chip, and the THz spectrum was obtained via the THz-TDS system without an electric field. Then, an electric field of 2500V/cm was applied parallel to the microfluidic chip, and the guar gum solution was placed in the electric field for 5 min. The power supply was then disconnected, the electrode plate was removed, and the THz spectrum was obtained with the THz-TDS system. Next, the microfluidic chip was shaken to return the sample to the original state as much as possible, the sample was placed in the electric field for 10 min, and the THz spectrum was obtained again. The THz spectra obtained in these three measurements are shown in Fig. 10. The results show that the THz transmittance increases with an increasing duration of electric field exposure, implying that the THz absorption intensity of the guar gum solution decreases.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe THz spectra of guar gum solution at varying temperatures show that the THz transmittance decreases with increasing temperature. This result occurs because the outer layer of hydroxyl, alkoxy and oxygen atoms in glycoside bonds in guar gum molecules containing sp\u003csup\u003e3\u003c/sup\u003e hybrid orbitals. The unshared lone electron pairs in the orbitals can combine with partially positively charged hydrogen in the water molecule to form hydrogen bonds through electrostatic attraction [13]. Due to the stretching of guar gum molecules, a variety of groups are fully exposed. The polar groups and polar water molecules interact with each other by hydrogen bonding or dipole forces to form an inner-layer water film. The inner-layer water reacts with the outer-layer water to form an association. The sol molecules with a large volume act as the skeleton, a large amount of water is bound, and free movement of the medium is hindered, resulting in resistance between laminar flows. This resistance is exhibited as apparent viscosity, which causes the solution to display a quantitative viscosity [14]. When the temperature rises, the rate of molecular motion gradually increases, and the aggregates change from large to small. With an increase in absorbed energy, the structure of the system breaks down, and the viscosity decreases. In this process, the oxidative degradation of guar gum molecules leads to hydrogen bond breaking [14], and the THz transmission intensity should be enhanced. However, guar gum solution is a polar liquid in which dipole interactions occur. The absorption coefficient of polar liquids is larger in the THz range approximately 10\u0026ndash;100 times that of non-polar liquids [15]. Therefore, the vibration between dipole molecules is the main reason that the THz absorption of guar gum increases with increasing temperature.\u003c/p\u003e\n\u003cp\u003eThe THz transmission spectra of guar gum solution for varying concentrations (Fig. 9) show that the transmission intensity of THz waves decreases with increasing concentration; consequently, the THz absorption of guar gum solution increases. This result is due to the existence of hydrogen bonds between the guar gum molecules. An increase in the guar gum concentration leads to a higher number of hydrogen bonds, which in turn increases the absorption of THz waves. In addition, the vibration interactions between dipole molecules in the polar guar gum liquid also contribute to the increased THz absorption [15].\u003c/p\u003e\n\u003cp\u003eThe THz transmission spectra of guar gum solution exposed to an electric field for varying durations (Fig. 10) indicate that a longer exposure to an electric field results in a higher THz transmission intensity for guar gum solution. This result occurs because the applied electric field can reduce hydrogen bonding and increase the diffusion coefficient of water molecules [16]. Therefore, it can be preliminarily concluded that the external electric field reduces the effect of hydrogen bonds in the sample, which increases the THz transmission; thus, the THz absorption intensity decreases as the duration of external electric field exposure increases.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this paper, a new method for fabricating a THz microfluidic chip is proposed. A double-sided adhesive was used as the channel interlayer of the microfluidic chip, which greatly shortens the fabrication time and resolves the issue of chip leakage. A high-precision temperature control system was designed to control the temperature of guar gum solution, and a high-voltage power supply was used to provide a strong electric field. The THz transmission characteristics of guar gum solution were measured for different temperatures, concentrations and electric field exposure durations via a THz-TDS system, which indirectly reflected the THz absorption characteristics of guar gum.\u003c/p\u003e\n\u003cp\u003eThe results show that the transmission intensity of THz waves in guar gum solution decreases with increasing temperature and concentration. This phenomenon was attributed to the viscosity of guar gum, the number of hydrogen bonds in solution and the vibration of dipole molecules. In addition, as the duration of electric field exposure increased, the THz transmittance of the guar gum solution increased, which was attributed to hydrogen bonds. This study expands the potential applications for THz technology and lays a foundation for the study of colloidal properties using THz methods.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003ePBS: polarisation beam splitter; PCA: Photoconductive Antenna; PID: Proportion Integration Differentiation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank \u0026lsquo;enago\u0026rsquo; for providing English touch up.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the theoretical analysis, calculations, experiment and preparation of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China under Grant No. 61575131.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformation about data was detailed in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor details\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eKey Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing 100048, China\u003cem\u003e.\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003eBeijing Key Laboratory of Terahertz Spectroscopy and Imaging, Beijing 100048, China\u003cem\u003e.\u003c/em\u003e\u003csup\u003e3\u003c/sup\u003eBeijing Advanced Innovation Center for Imaging Theory and Technology, Beijing 100048, China\u003cem\u003e.\u003c/em\u003e\u003csup\u003e4\u003c/sup\u003eDepartment of Physics, Capital Normal University, Beijing 100048, China.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGu,H., Shi,C., Wu,X., Peng,Y.: Molecular methylation detection based on terahertz metamaterial technology . Analyst. 145 (20), 6705-6712 (2020)\u003c/li\u003e\n\u003cli\u003eZhou,R., Wang,C., Xu,W., Xie,L.: Biological applications of terahertz technology based on nanomaterials and nanostructures. Nanoscale. 11(8), 3445-3457 (2019)\u003c/li\u003e\n\u003cli\u003eMa,Y., Huang,H., Hao,S., Qiu,K., Zheng,Z.: Insights into the water status in hydrous minerals using terahertz time-domain spectroscopy. Sci. Rep. 9 (1), 9265 (2019)\u003c/li\u003e\n\u003cli\u003eGallerano,G., Doria,A., Giovenale,E.: Photopolymer fiber fiber based on fiber fiber fiber. J. Opt. 4 (1), 17-24 (2014)\u003c/li\u003e\n\u003cli\u003eBennett,D., Taylor,Z.,Tewari,P., Sung,S., Maccabi,A., Singh,R.: Assessment of Corneal Hydration in the Terahertz band. J. Bio. Opt. 17 (9), 097008 (2012)\u003c/li\u003e\n\u003cli\u003eShiraga,K., Ogawa,Y., Kondo,N., Irisawa,A., Imamura,M.: Hydration of saccharides via attenuated terahertz temporal-domain reflection spectroscopy. Food Chem. 140 (2) , 315 (2013)\u003c/li\u003e\n\u003cli\u003eDuponchel,L., Laurette,S., Hatirnaz,B., Treizebre,A., Affouard,F., Bocquet,B.: Terahertz microfluidic sensor for in situ exploration of hydration shell of molecules. Chemometr Intell LAB. 123 28-35 (2013)\u003c/li\u003e\n\u003cli\u003eYang,J., Li,S., Zhao,H., Zhang,J., Yang,N., Jing,D., Wang,C., Han,J.: Terahertz spectroscopy of L-asparagine and its monohydrate. Acta Physica Sinica. 63 (13) 105-111 (2014)\u003c/li\u003e\n\u003cli\u003eFischer,B., Walther,M., Jepsen,P.: Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy. Phys. Med. Biol. 47 (21), 3807 (2002)\u003c/li\u003e\n\u003cli\u003eSerita,K., Tonouchi,M.: A Terahertz Microfluidic Chip for Ultra-trace Biosensing.Nippon Laser Igakkaishi. 39(4), 329-334 (2019)\u003c/li\u003e\n\u003cli\u003eBaragwanath,A., Swift,G., Dai,D., Gallant,A., Chamberlain,J.: Silicon based microfluidic cell for terahertz frequencies. Jpn J Appl Phys. 108(1) 013102-013102-8 (2010)\u003c/li\u003e\n\u003cli\u003eWang,X.: Preparation of Modified Guar Gum and Its Application in Reactive Dye Printing of Cotton Fabrics. Zhejiang Sci-Tech University (2017)\u003c/li\u003e\n\u003cli\u003eXie,J., Liu,S., Gu,Z.: Study on factors affecting the rheological properties of guar gum. Guangzhou Food Industry Science and Technology. 1007-2764 (2004)\u003c/li\u003e\n\u003cli\u003eWu,X.: Preparation of Guar gum modified adhesive and its application in textile field. Suzhou University(2018)\u003c/li\u003e\n\u003cli\u003eSon,J.: Terahertz Biomedical Science and Technology. CRC Press. 347-350 (2014)\u003c/li\u003e\n\u003cli\u003eYang,Z., Chai,Z., Zhang,H.: Effect of electric field on water diffusion on kaolinite surface. Meitan Xuebao. 11(2020)\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-european-optical-society-rapid-publications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jeos","sideBox":"Learn more about [Journal of the European Optical Society-Rapid Publications](http://jeos.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/JEOS/default.aspx","title":"Journal of the European Optical Society-Rapid Publications","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Terahertz, Guar gum, Microfluidic chip, Temperature, Concentration, Electric field ","lastPublishedDoi":"10.21203/rs.3.rs-302211/v2","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-302211/v2","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe vibrational energy levels of many biomolecules correspond to the terahertz band; thus, terahertz technology can be used to identify these substances. Moreover, as the biological activity of most biomolecules can be observed only in aqueous solution, the characteristics of such biomolecules must be studied in aqueous solution. In this study, a simple microfluidic chip, a temperature control device and a strong electric field device were designed to study the terahertz absorption characteristics of guar gum for different temperatures, concentrations and electric field exposure durations, thus enabling the use of terahertz technology to analyse the characteristics of guar gum.\u003c/p\u003e","manuscriptTitle":"Terahertz absorption characteristics of guar gum determined via microfluidic technology","msid":"","msnumber":"","nonDraftVersions":[{"code":"","date":"2021-07-07 15:56:08","doi":"","editorialEvents":[{"type":"decision","content":"Accept","date":"2021-07-07T15:56:08+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-06-29T00:00:00+00:00","index":4,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2021-06-29T00:00:00+00:00","index":2,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2021-06-27T00:00:00+00:00","index":4,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2021-06-25T00:00:00+00:00","index":3,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-06-25T00:00:00+00:00","index":3,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2021-06-23T00:00:00+00:00","index":2,"fulltext":""},{"type":"editorAssigned","content":"","date":"2021-06-22T00:00:00+00:00","index":"","fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-06-22T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-06-22T00:00:00+00:00","index":0,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2021-06-22T00:00:00+00:00","index":1,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-06-22T00:00:00+00:00","index":1,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"checksComplete","content":"","date":"2021-06-21T23:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2021-06-21T23:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of the European Optical Society-Rapid Publications","date":"2021-06-17T04:03:09+00:00","index":"","fulltext":""},{"type":"notPreprinted","content":""}],"status":"timeline","journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-european-optical-society-rapid-publications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jeos","sideBox":"Learn more about [Journal of the European Optical Society-Rapid Publications](http://jeos.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/JEOS/default.aspx","title":"Journal of the European Optical Society-Rapid Publications","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}},{"code":2,"date":"2021-04-19 19:18:36","doi":"10.21203/rs.3.rs-302211/v2","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2021-05-20T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-05-19T00:00:00+00:00","index":4,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2021-05-08T00:00:00+00:00","index":2,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2021-05-04T00:00:00+00:00","index":3,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2021-04-21T00:00:00+00:00","index":4,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2021-04-20T00:00:00+00:00","index":3,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-04-20T00:00:00+00:00","index":1,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2021-04-19T01:00:00+00:00","index":2,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-04-19T00:00:00+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-04-19T00:00:00+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2021-04-19T00:00:00+00:00","index":1,"fulltext":""},{"type":"editorInvited","content":"","date":"2021-04-16T00:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-04-15T00:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2021-04-14T23:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of the European Optical Society-Rapid Publications","date":"2021-03-08T06:27:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-european-optical-society-rapid-publications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jeos","sideBox":"Learn more about [Journal of the European Optical Society-Rapid Publications](http://jeos.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/JEOS/default.aspx","title":"Journal of the European Optical Society-Rapid Publications","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}},{"code":"","date":"2021-04-19 00:00:00","doi":"","editorialEvents":[{"type":"decision","content":"Withdrawn by author","date":"2021-04-19T00:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-03-11T00:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2021-03-10T23:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2021-03-10T23:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2021-03-05T00:00:00+00:00","index":"","fulltext":""}],"status":"private","journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-european-optical-society-rapid-publications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jeos","sideBox":"Learn more about [Journal of the European Optical Society-Rapid Publications](http://jeos.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/JEOS/default.aspx","title":"Journal of the European Optical Society-Rapid Publications","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}},{"code":1,"date":"2021-03-19 21:33:41","doi":"10.21203/rs.3.rs-302211/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Withdrawn by author","date":"2021-04-19T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2021-03-22T00:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-03-11T00:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2021-03-09T11:40:40+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2021-03-05T00:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-european-optical-society-rapid-publications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jeos","sideBox":"Learn more about [Journal of the European Optical Society-Rapid Publications](http://jeos.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/JEOS/default.aspx","title":"Journal of the European Optical Society-Rapid Publications","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"beded3e1-d4f8-4d7a-a4c6-84eef41fb6ce","owner":[],"postedDate":"April 19th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":3747943,"name":"Materials Chemistry"}],"tags":[],"updatedAt":"2021-08-22T15:09:51+00:00","versionOfRecord":{"articleIdentity":"rs-302211","link":"https://doi.org/10.1186/s41476-021-00162-x","journal":{"identity":"journal-of-the-european-optical-society-rapid-publications","isVorOnly":false,"title":"Journal of the European Optical Society-Rapid Publications"},"publishedOn":"2021-08-11 15:01:20","publishedOnDateReadable":"August 11th, 2021"},"versionCreatedAt":"2021-04-19 19:18:36","video":"","vorDoi":"10.1186/s41476-021-00162-x","vorDoiUrl":"https://doi.org/10.1186/s41476-021-00162-x","workflowStages":[]},"version":"v2","identity":"rs-302211","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-302211","identity":"rs-302211","version":["v2"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}