{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T04:19:34Z","timestamp":1790050774032,"version":"4.0.1"},"reference-count":27,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T00:00:00Z","timestamp":1768694400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>In recent years, diagnostic technologies that utilize noninvasively collected sweat have garnered significant interest. However, the concentration of components in sweat is lower than that in blood, making the introduction of a concentration step as a sample pretreatment crucial for achieving highly sensitive detection. In this study, we developed a PDMS-based microchannel filled with silica gel, a desiccant particle, to concentrate liquid samples at room temperature without requiring an external power source or heating. The evaluation of the basic characteristics of the fabricated microchannel confirmed that filling it with silica gel efficiently removed the solvent vapor from the liquid samples. In concentration tests using the fluorescent dye uranine as a model for sweat sugar, a maximum 1.4-fold concentration was achieved in DPBS solution and a 1.2-fold concentration in artificial sweat at room temperature. In contrast, no similar concentration effect was observed in microchannels without silica gel packing. The proposed silica-gel-packed PDMS microchannel features a simple structure and requires no external equipment, making it easily integrable with existing microfluidic devices as a sample pretreatment module. This method is considered useful as a passive and simple sample concentration technique for the analysis of low-molecular-weight components in sweat.<\/jats:p>","DOI":"10.3390\/polym18020260","type":"journal-article","created":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T09:57:02Z","timestamp":1768816622000},"page":"260","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Power-Free Sweat Sample Concentration Using a Silica-Gel-Packed PDMS Microchannel"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8218-3426","authenticated-orcid":false,"given":"Hirotada","family":"Hirama","sequence":"first","affiliation":[{"name":"Integrated Research Center for Self-Care Technology, National Institute of Advanced Industrial Science and Technology, Chiba 277-0882, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masanori","family":"Hayase","sequence":"additional","affiliation":[{"name":"Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Marrugo-Ram\u00edrez, J., Mir, M., and Samitier, J. (2018). Blood-Based Cancer Biomarkers in Liquid Biopsy: A Promising Non-Invasive Alternative to Tissue Biopsy. Int. J. Mol. Sci., 19.","DOI":"10.3390\/ijms19102877"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"389","DOI":"10.1038\/s41587-019-0045-y","article-title":"Wearable biosensors for healthcare monitoring","volume":"37","author":"Kim","year":"2019","journal-title":"Nat. Biotechnol."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Sierra, J., Marrugo-Ramirez, J., Rodr\u00edguez-Trujillo, R., Mir, M., and Samitier, J. (2020). Sensor-Integrated Microfluidic Approaches for Liquid Biopsies Applications in Early Detection of Cancer. Sensors, 20.","DOI":"10.3390\/s20051317"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1186\/s12935-019-1067-8","article-title":"Circulating tumor cells in precision oncology: Clinical applications in liquid biopsy and 3D organoid model","volume":"19","author":"Yang","year":"2019","journal-title":"Cancer Cell Int."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1515","DOI":"10.1039\/C7AN01945A","article-title":"Mobile diagnostics: Next-generation technologies for in vitro diagnostics","volume":"143","author":"Shin","year":"2018","journal-title":"Analyst"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"368","DOI":"10.1038\/nature05058","article-title":"The origins and the future of microfluidics","volume":"442","author":"Whitesides","year":"2006","journal-title":"Nature"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.mee.2014.10.013","article-title":"Lab-on-a-chip devices: How to close and plug the lab?","volume":"132","author":"Temiz","year":"2015","journal-title":"Microelectron. Eng."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"3558","DOI":"10.1039\/C7LC00592J","article-title":"Microfluidics for exosome isolation and analysis: Enabling liquid biopsy for personalized medicine","volume":"17","author":"Wu","year":"2017","journal-title":"Lab A Chip"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2178","DOI":"10.1039\/C8LC00530C","article-title":"A fluorometric skin-interfaced microfluidic device and smartphone imaging module for in situ quantitative analysis of sweat chemistry","volume":"18","author":"Sekine","year":"2018","journal-title":"Lab A Chip"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1038\/nature16521","article-title":"Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis","volume":"529","author":"Gao","year":"2016","journal-title":"Nature"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"14803","DOI":"10.1021\/acs.analchem.9b03110","article-title":"Microfluidic Chip-Based Wearable Colorimetric Sensor for Simple and Facile Detection of Sweat Glucose","volume":"91","author":"Xiao","year":"2019","journal-title":"Anal. Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"e1601314","DOI":"10.1126\/sciadv.1601314","article-title":"Wearable\/disposable sweat-based glucose monitoring device with multistage transdermal drug delivery module","volume":"3","author":"Lee","year":"2017","journal-title":"Sci. Adv."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Ibrahim, N.F.A., Sabani, N., Johari, S., Abd Manaf, A., Wahab, A.A., Zakaria, Z., and Noor, A.M. (2022). A Comprehensive Review of the Recent Developments in Wearable Sweat-Sensing Devices. Sensors, 22.","DOI":"10.3390\/s22197670"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"6893","DOI":"10.1021\/acs.analchem.2c01052","article-title":"Low-Cost Wearable Fluidic Sweat Collection Patch for Continuous Analyte Monitoring and Offline Analysis","volume":"94","author":"Steijlen","year":"2022","journal-title":"Anal. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1038\/s41378-022-00443-6","article-title":"Wearable and flexible electrochemical sensors for sweat analysis: A review","volume":"9","author":"Gao","year":"2023","journal-title":"Microsyst. Nanoeng."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"125967","DOI":"10.1016\/j.talanta.2024.125967","article-title":"A wearable microfluidic system for efficient sweat collection and real-time detection","volume":"274","author":"Yin","year":"2024","journal-title":"Talanta"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"034106","DOI":"10.1063\/5.0208075","article-title":"Microfluidic sweat patch based on capillary force and evaporation pump for real-time continuous sweat analysis","volume":"18","author":"Fu","year":"2024","journal-title":"Biomicrofluidics"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Chen, X.M., Li, Y.J., Han, D., Zhu, H.C., Xue, C.D., Chui, H.C., Cao, T., and Qin, K.R. (2019). A Capillary-Evaporation Micropump for Real-Time Sweat Rate Monitoring with an Electrochemical Sensor. Micromachines, 10.","DOI":"10.3390\/mi10070457"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2524","DOI":"10.1039\/D1LC00328C","article-title":"Bio-inspired fractal textile device for rapid sweat collection and monitoring","volume":"21","author":"Chen","year":"2021","journal-title":"Lab A Chip"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"e2302173","DOI":"10.1002\/adhm.202302173","article-title":"Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis","volume":"13","author":"Zheng","year":"2024","journal-title":"Adv. Healthc. Mater"},{"key":"ref_21","unstructured":"Xu, W., L Wu, L., Li, G.P., and Bachman, M. (2010, January 3\u20137). A vapor based microfluidic sample concentrator. Proceedings of the 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences, Groningen, The Netherlands."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"550","DOI":"10.1002\/(SICI)1521-3773(19980316)37:5<550::AID-ANIE550>3.0.CO;2-G","article-title":"Soft lithography","volume":"37","author":"Xia","year":"1998","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"6544","DOI":"10.1021\/ac0346712","article-title":"Solvent Compatibility of Poly(dimethylsiloxane)-Based Microfluidic Devices","volume":"75","author":"Lee","year":"2003","journal-title":"Anal. Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"415","DOI":"10.1002\/(SICI)1099-0488(20000201)38:3<415::AID-POLB8>3.0.CO;2-Z","article-title":"Gas sorption, diffusion, and permeation in poly(dimethylsiloxane)","volume":"38","author":"Merkel","year":"2000","journal-title":"J. Polym. Sci. Pol. Phys."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"11981","DOI":"10.1021\/ac503751a","article-title":"Evaporative Concentration on a Paper-Based Device to Concentrate Analytes in a Biological Fluid","volume":"86","author":"Wong","year":"2014","journal-title":"Anal. Chem."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"7847","DOI":"10.1021\/acs.analchem.7b01988","article-title":"Nonocclusive Sweat Collection Combined with Chemical Isotope Labeling LC-MS for Human Sweat Metabolomics and Mapping the Sweat Metabolomes at Different Skin Locations","volume":"89","author":"Hooton","year":"2017","journal-title":"Anal. Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1603","DOI":"10.1126\/science.1182383","article-title":"Materials and Mechanics for Stretchable Electronics","volume":"327","author":"Rogers","year":"2010","journal-title":"Science"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/2\/260\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T10:06:19Z","timestamp":1768817179000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/2\/260"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,18]]},"references-count":27,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["polym18020260"],"URL":"https:\/\/doi.org\/10.3390\/polym18020260","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,18]]}}}