[{"oa_version":"Published Version","acknowledgement":"The authors gratefully acknowledge help from Dr. Benjamin Seelbinder, Mr. Claudius George, and Mr. Falk Elsner in designing and constructing the magnetic needle for force-driven rheology experiments. We thank Dr. Iain Patten for valuable discussions on the structure of the manuscript and Mr. Ivan Saraev for graphics support. I.D.S. and M.K. kindly acknowledge funding from the Life grant by Volkswagen Foundation (Life! grant no. 92772), Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, Germany's Excellence Strategy, 2082/1 and grant no. 515462906), and the Hector Foundation. I.D.S. was additionally funded by the Karlsruhe Institute of Technology (Excellence Strategy via the Young Investigator Group Preparation Program). V.R.K., S.W., and M.K. thank the ERC Starting Grant GHOSTs (grant no. 853619).","researchdata_availability":"yes","publisher":"Oxford University Press","date_published":"2026-06-01T00:00:00Z","file":[{"access_level":"open_access","creator":"dernst","date_created":"2026-07-13T13:13:56Z","file_id":"22312","relation":"main_file","date_updated":"2026-07-13T13:13:56Z","file_name":"2026_PNASNexus_Stoev.pdf","file_size":3073062,"success":1,"checksum":"bb2c89ea73da762ad6423ac299ac3533","content_type":"application/pdf"}],"biorxivid":1,"title":"Active and probe-free intracellular rheology via phase-sensitive thermoviscous flows","_id":"22297","issue":"6","DOAJ_listed":"1","keyword":["cell mechanics","active microrheology","noninvasiveness","thermoviscous flows","FLUCS"],"PlanS_conform":"1","date_created":"2026-07-13T09:50:12Z","OA_type":"gold","file_date_updated":"2026-07-13T13:13:56Z","quality_controlled":"1","department":[{"_id":"CaHe"}],"supplementarymaterial":"yes","citation":{"ieee":"I. D. Stoev <i>et al.</i>, “Active and probe-free intracellular rheology via phase-sensitive thermoviscous flows,” <i>PNAS Nexus</i>, vol. 5, no. 6. Oxford University Press, 2026.","chicago":"Stoev, Iliya D, Madison Bolger-Munro, Antonio Minopoli, Susan Wagner, Venkat Raghavan Krishnaswamy, Elena Erben, Kai Weißenbruch, et al. “Active and Probe-Free Intracellular Rheology via Phase-Sensitive Thermoviscous Flows.” <i>PNAS Nexus</i>. Oxford University Press, 2026. <a href=\"https://doi.org/10.1093/pnasnexus/pgag190\">https://doi.org/10.1093/pnasnexus/pgag190</a>.","mla":"Stoev, Iliya D., et al. “Active and Probe-Free Intracellular Rheology via Phase-Sensitive Thermoviscous Flows.” <i>PNAS Nexus</i>, vol. 5, no. 6, pgag190, Oxford University Press, 2026, doi:<a href=\"https://doi.org/10.1093/pnasnexus/pgag190\">10.1093/pnasnexus/pgag190</a>.","short":"I.D. Stoev, M. Bolger-Munro, A. Minopoli, S. Wagner, V.R. Krishnaswamy, E. Erben, K. Weißenbruch, N. Maghelli, M. Bastmeyer, C.-P.J. Heisenberg, M. Kreysing, PNAS Nexus 5 (2026).","apa":"Stoev, I. D., Bolger-Munro, M., Minopoli, A., Wagner, S., Krishnaswamy, V. R., Erben, E., … Kreysing, M. (2026). Active and probe-free intracellular rheology via phase-sensitive thermoviscous flows. <i>PNAS Nexus</i>. Oxford University Press. <a href=\"https://doi.org/10.1093/pnasnexus/pgag190\">https://doi.org/10.1093/pnasnexus/pgag190</a>","ista":"Stoev ID, Bolger-Munro M, Minopoli A, Wagner S, Krishnaswamy VR, Erben E, Weißenbruch K, Maghelli N, Bastmeyer M, Heisenberg C-PJ, Kreysing M. 2026. Active and probe-free intracellular rheology via phase-sensitive thermoviscous flows. PNAS Nexus. 5(6), pgag190.","ama":"Stoev ID, Bolger-Munro M, Minopoli A, et al. Active and probe-free intracellular rheology via phase-sensitive thermoviscous flows. <i>PNAS Nexus</i>. 2026;5(6). doi:<a href=\"https://doi.org/10.1093/pnasnexus/pgag190\">10.1093/pnasnexus/pgag190</a>"},"oa":1,"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_updated":"2026-07-13T13:14:43Z","OA_place":"publisher","scopus_import":"1","status":"public","license":"https://creativecommons.org/licenses/by/4.0/","ddc":["570"],"language":[{"iso":"eng"}],"year":"2026","article_number":"pgag190","abstract":[{"text":"Determination of the rheological properties of cells is known to require active measurements, which largely depend on the internalization of mechanical probes. Here, we circumvent this problem via the introduction of Rheological focused light-induced cytoplasmic streaming (Rheo-FLUCS): an active, yet probe-free approach that leverages light-induced flows to access mechanical changes in complex systems. While Rheo-FLUCS is facilitated by thermoviscous expansion phenomena rather than external forces, here we show equivalence in its ability to measure relative viscoelastic properties. Specifically, we demonstrate a phase-lag equivalence with probe-dependent active microrheology in a wide range of physically different, yet chemically identical materials. We exemplify the utility of Rheo-FLUCS in three distinctly different biological systems: compound-treated mouse fibroblasts (NIH-3T3), genetically modified human osteoblasts (U2OS) to elucidate the role of myosins in cytoplasmic mechanics, and early ascidian oocytes of Phallusia mammillata at fertilization stage. Our biological use-cases exemplify the application versatility of Rheo-FLUCS, which in the future may use phase information as a marker for developmental success.","lang":"eng"}],"article_processing_charge":"Yes","publication":"PNAS Nexus","external_id":{"biorxivid":["10.1101/2025.04.07.647540"]},"has_accepted_license":"1","publication_status":"published","type":"journal_article","article_type":"original","dataavailabilitystatement":"All data and materials are made available on Zenodo public repository under Creative Commons Attribution 4.0 International License: https://doi.org/10.5281/zenodo.20322020.","month":"06","doi":"10.1093/pnasnexus/pgag190","das_tickbox":"1","day":"01","intvolume":"         5","volume":5,"author":[{"first_name":"Iliya D","full_name":"Stoev, Iliya D","last_name":"Stoev"},{"full_name":"Bolger-Munro, Madison","last_name":"Bolger-Munro","id":"516F03FA-93A3-11EA-A7C5-D6BE3DDC885E","first_name":"Madison","orcid":"0000-0002-8176-4824"},{"full_name":"Minopoli, Antonio","last_name":"Minopoli","first_name":"Antonio"},{"last_name":"Wagner","full_name":"Wagner, Susan","first_name":"Susan"},{"last_name":"Krishnaswamy","full_name":"Krishnaswamy, Venkat Raghavan","first_name":"Venkat Raghavan"},{"first_name":"Elena","full_name":"Erben, Elena","last_name":"Erben"},{"last_name":"Weißenbruch","full_name":"Weißenbruch, Kai","first_name":"Kai"},{"first_name":"Nicola","last_name":"Maghelli","full_name":"Maghelli, Nicola"},{"full_name":"Bastmeyer, Martin","last_name":"Bastmeyer","first_name":"Martin"},{"id":"39427864-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0002-0912-4566","first_name":"Carl-Philipp J","full_name":"Heisenberg, Carl-Philipp J","last_name":"Heisenberg"},{"last_name":"Kreysing","full_name":"Kreysing, Moritz","first_name":"Moritz"}],"publication_identifier":{"eissn":["2752-6542"]},"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","short":"CC BY (4.0)","image":"/images/cc_by.png"}}]