Digital holography for the reconstruction of particles suspended in diamagnetic drops levitated in a magneto-gravitational trap

Digital holography for the reconstruction of particles suspended in diamagnetic drops levitated in a magneto-gravitational trap | 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 Article Digital holography for the reconstruction of particles suspended in diamagnetic drops levitated in a magneto-gravitational trap Sofia Biscotti This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9702689/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The magneto‑gravitational trap developed in this work enables the stable levitation of millimetric diamagnetic microdroplets, allowing non‑invasive analysis of the particles suspended within them. Levitation is achieved by combining the gravitational potential with the magnetic contribution generated by an anti‑Helmholtz coil pair, which together create a local minimum of the total potential. The optical system is designed to provide uniform illumination of the levitated droplet: a beam modulated by an SLM passes through a half‑wave plate, is split by a polarizing beam splitter, recombined with a pump beam, and expanded to illuminate the entire trapping region. A dichroic mirror directs the wavelength of interest toward the sample while simultaneously transmitting the scattered light to the CCD, and a second laser supplies the reference beam for digital holography. An ultrasonic horn, coupled to metallic electrodes, introduces the droplet into the levitation region and can generate a controlled acoustic flow to gently redistribute the internal particles before acquisition. The overall architecture integrates magnetic, acoustic, and optical manipulation of the droplet into a single system, enabling precise control over both the sample position and the internal fluid conditions. This synergy makes it possible to explore experimental configurations that would be unattainable with conventional approaches. Three‑dimensional reconstruction of the complex optical field is performed through Fresnel propagation in the paraxial regime, producing amplitude and phase maps at multiple propagation distances. To identify the plane in which the suspended particles appear most sharply resolved, a focus metric based on the discrete wavelet transform is employed. This measurement exhibits a clear maximum at the focal plane, providing robust and computationally efficient axial localization. This conceptual framework lays the foundation for a new methodology dedicated to the three‑dimensional characterization of particles and microstructures within levitated water droplets. Optics/Lasers Optical Materials and Devices Nanoscience Magnetics Materials and Devices Digital holography Optical imaging Optical Fourier transform Physical optics Light propagation Photonics Optics Full Text Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted 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. 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-9702689","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":639663107,"identity":"a2922b2b-1e40-47f7-b66e-3b853ade3c09","order_by":0,"name":"Sofia Biscotti","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYBACA2YIzcPAwPjgAAOPDZDN2HiAsJYEA6AWZoMDDDJpIC0N+LUwQLQwgLQwMNgcBvPxajFnZ3/44eOPPzLy7c2MB37knLdb234YaEuNTTQuLZbNPMaSM4AOMzhzmOFgz5nbydvOJAK1HEvLbcDlsMM8bMw8IC0S+QcO8PbcTjY7ANTC2HAYjxb2Z2At8jOSGQ7+/Xcu2ez8Q0JaGMzAWhhuJDMc5uE5YGd2g4AtEL+kGYP9cliGJznB7AbQlgQ8fjHnP/7wwwcbOXtgiDF/fMNjZ292Pv3hgw81Nji1YIBEsMoEYpWDgD0pikfBKBgFo2BkAACq1F/QQjTbogAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0009-0004-4371-772X","institution":"None","correspondingAuthor":true,"prefix":"","firstName":"Sofia","middleName":"","lastName":"Biscotti","suffix":""}],"badges":[],"createdAt":"2026-05-13 10:52:53","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-9702689/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9702689/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109296955,"identity":"1f251558-cf5e-498c-92f0-6c125b5fd065","added_by":"auto","created_at":"2026-05-15 08:52:18","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1022186,"visible":true,"origin":"","legend":"","description":"","filename":"HolographicImagingofParticlesinMagnetoGravitationalTrapsS.Biscotti.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9702689/v1_covered_0600c293-5baf-4053-a360-86f98e7150c6.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eDigital holography for the reconstruction of particles suspended in diamagnetic drops levitated in a magneto-gravitational trap\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Digital holography, Optical imaging, Optical Fourier transform, Physical optics, Light propagation, Photonics, Optics","lastPublishedDoi":"10.21203/rs.3.rs-9702689/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9702689/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe magneto‑gravitational trap developed in this work enables the stable levitation of millimetric diamagnetic microdroplets, allowing non‑invasive analysis of the particles suspended within them. 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