{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,3]],"date-time":"2026-02-03T17:11:08Z","timestamp":1770138668586,"version":"3.49.0"},"reference-count":61,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2023,8,25]],"date-time":"2023-08-25T00:00:00Z","timestamp":1692921600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Institutes of Alcohol Abuse and Alcoholism of the National Institutes of Health","award":["R44AA026125"],"award-info":[{"award-number":["R44AA026125"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>New transdermal biosensors measure analytes that diffuse from the bloodstream through the skin, making it important to reduce the system response time and understand measurement output. While highly customized models have been created for specific sensors, a generalized model for transdermal sensor systems is lacking. Here, a simple one-dimensional diffusion model was used to characterize the measurement system and classify biosensors as either flux types or concentration types. Results showed that flux-type sensors have significantly faster response times than concentration sensors. Furthermore, flux sensors do not measure concentration, but rather have an output measurement that is proportional to skin permeability. These findings should lead to an improved understanding of transdermal measurements and their relation to blood analyte concentration. In the realm of alcohol research, where the majority of commercially available sensors are flux types, our work advocates toward moving away from transdermal alcohol concentration as a metric, and instead suggests embracing transdermal alcohol flux as a more suitable alternative.<\/jats:p>","DOI":"10.3390\/bios13090845","type":"journal-article","created":{"date-parts":[[2023,8,25]],"date-time":"2023-08-25T08:42:20Z","timestamp":1692952940000},"page":"845","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Flux-Type versus Concentration-Type Sensors in Transdermal Measurements"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2968-7152","authenticated-orcid":false,"given":"Bob M.","family":"Lansdorp","sequence":"first","affiliation":[{"name":"Milo Sensors, Inc., Santa Barbara, CA 93101, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"385","DOI":"10.3390\/diagnostics3040385","article-title":"Continuous glucose monitoring systems: A review","volume":"3","author":"Vashist","year":"2013","journal-title":"Diagnostics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.coelec.2019.04.003","article-title":"Microneedle-based electrochemical devices for transdermal biosensing: A review","volume":"16","author":"Tasca","year":"2019","journal-title":"Curr. Opin. Electrochem."},{"key":"ref_3","unstructured":"Food, U., and Administration, D. (2023, March 17). Regulatory Considerations for Microneedling Products\u2014Guidance for Industry and Food and Drug Administration Staff, Available online: https:\/\/www.fda.gov\/media\/107708\/download."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/j.jconrel.2016.12.007","article-title":"Transdermal reverse iontophoresis A novel technique for therapeutic drug monitoring","volume":"246","author":"Giri","year":"2017","journal-title":"J. Control. Release"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1002\/pdi.339","article-title":"Potential impact of a new blood glucose monitoring device: The GlucoWatch\u00ae Biographer","volume":"19","author":"Chan","year":"2002","journal-title":"Pract. Diabetes Int."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Children Network (DirecNet) Study Group (2005). A randomized multicenter trial comparing the GlucoWatch Biographer with standard glucose monitoring in children with type 1 diabetes. Diabetes Care, 28, 1101\u20131106.","DOI":"10.2337\/diacare.28.5.1101"},{"key":"ref_7","unstructured":"Wimmer, N.J., Robbins, S., Ssemaganda, H., Yang, E., Normand, S.L., Matheny, M.E., Herz, N., Rising, J., and Resnic, F.S. (2016). Assessing the cost burden of United States FDA-mandated post-approval studies for medical devices. J. Health Care Financ., 2016."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"385","DOI":"10.1007\/BF02474218","article-title":"A light emitting diode skin reflectance oximeter","volume":"10","author":"Cohen","year":"1972","journal-title":"Med. Biol. Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1007\/BF02442476","article-title":"Spectrophotometric monitoring of arterial oxygen saturation in the fingertip","volume":"18","author":"Yoshiya","year":"1980","journal-title":"Med. Biol. Eng. Comput."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"054039","DOI":"10.1117\/1.3253353","article-title":"Comparison of spectroscopically measured tissue alcohol concentration to blood and breath alcohol measurements","volume":"14","author":"Ridder","year":"2009","journal-title":"J. Biomed. Opt."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"160","DOI":"10.1038\/s41928-018-0043-y","article-title":"Wearable sweat sensors","volume":"1","author":"Bariya","year":"2018","journal-title":"Nat. Electron."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.mbs.2014.05.001","article-title":"A two-phase two-layer model for transdermal drug delivery and percutaneous absorption","volume":"257","author":"Pontrelli","year":"2014","journal-title":"Math. Biosci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1016\/j.ijpharm.2011.02.023","article-title":"Mathematical models of skin permeability: An overview","volume":"418","author":"Mitragotri","year":"2011","journal-title":"Int. J. Pharm."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"495","DOI":"10.1111\/1523-1747.ep12470197","article-title":"The influence of stratum corneum morphology on water permeability","volume":"96","author":"Potts","year":"1991","journal-title":"J. Investig. Dermatol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"620","DOI":"10.1002\/jps.20509","article-title":"A Multiphase Microscopic Diffusion Model for Stratum Corneum permeability. I. Formulation, Solution, and Illustrative Results for Representative Compounds","volume":"95","author":"Wang","year":"2006","journal-title":"J. Pharm. Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"249","DOI":"10.1111\/j.1530-0277.1987.tb01300.x","article-title":"Ethanol vapor above skin: Determination by a gas sensor instrument and relationship with plasma concentration","volume":"11","author":"Giles","year":"1987","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_17","first-page":"449","article-title":"Feasibility of transdermal ethanol sensing for the detection of intoxicated drivers","volume":"51","author":"Webster","year":"2007","journal-title":"Ann. Adv. Automot. Med."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1152\/japplphysiol.00927.2005","article-title":"The kinetics of transdermal ethanol exchange","volume":"100","author":"Anderson","year":"2006","journal-title":"J. Appl. Physiol."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Rosen, I.G., Luczak, S.E., Hu, W., and Hankin, M. (2013, January 8\u201310). Discrete-time blind deconvolution for distributed parameter systems with dirichlet boundary input and unbounded output with application to a transdermal alcohol biosensor. Proceedings of the 2013 Conference on Control and Its Applications, SIAM, San Diego, CA, USA.","DOI":"10.1137\/1.9781611973273.22"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"911","DOI":"10.3934\/mbe.2016023","article-title":"Using drinking data and pharmacokinetic modeling to calibrate transport model and blind deconvolution based data analysis software for transdermal alcohol biosensors","volume":"13","author":"Dai","year":"2016","journal-title":"Math. Biosci. Eng. MBE"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5322","DOI":"10.1109\/JSEN.2020.3030254","article-title":"A discreet wearable iot sensor for continuous transdermal alcohol monitoring\u2014Challenges and opportunities","volume":"21","author":"Li","year":"2020","journal-title":"IEEE Sens. J."},{"key":"ref_22","unstructured":"Li, B. (2021). Perspiration Compensated Transdermal Alcohol Sensor for Personalized Medicine. [PhD Thesis, The George Washington University]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"108205","DOI":"10.1016\/j.drugalcdep.2020.108205","article-title":"Using machine learning for real-time BAC estimation from a new-generation transdermal biosensor in the laboratory","volume":"216","author":"Fairbairn","year":"2020","journal-title":"Drug Alcohol Depend."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"514","DOI":"10.1111\/acer.14794","article-title":"Examining features of transdermal alcohol biosensor readings: A promising approach with implications for research and intervention","volume":"46","author":"Fridberg","year":"2022","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1111\/acer.14804","article-title":"Sensitivity, specificity, and tolerability of the BACTrack Skyn compared to other alcohol monitoring approaches among young adults in a field-based setting","volume":"46","author":"Ash","year":"2022","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_26","unstructured":"Carter, M., Findlay, M., Peaslee, D., Ploense, L., Meulendyk, B., Devine, E., and Stetter, J.R. (2021). Electrochemical Society Meeting Abstracts 239, The Electrochemical Society, Inc."},{"key":"ref_27","unstructured":"Boyce, W.E., DiPrima, R.C., and Meade, D.B. (2001). Elementary Differential Equations and Boundary Value Problems, Wiley. [7th ed.]."},{"key":"ref_28","unstructured":"Daileda, R.C. (2023, April 04). Partial Differential Equations Lecture Notes. Available online: http:\/\/ramanujan.math.trinity.edu\/rdaileda\/teach\/s12\/m3357\/lectures\/lecture_2_28_short.pdf."},{"key":"ref_29","unstructured":"Crank, J. (1979). The Mathematics of Diffusion, Oxford University Press."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"702","DOI":"10.1152\/physrev.1971.51.4.702","article-title":"Permeability of the skin","volume":"51","author":"Scheuplein","year":"1971","journal-title":"Physiol. Rev."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1093\/alcalc\/agw058","article-title":"Time delays in transdermal alcohol concentrations relative to breath alcohol concentrations","volume":"52","author":"Roache","year":"2017","journal-title":"Alcohol Alcohol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Lansdorp, B., Ramsay, W., Hamid, R., and Strenk, E. (2019). Wearable enzymatic alcohol biosensor. Sensors, 19.","DOI":"10.20944\/preprints201904.0103.v1"},{"key":"ref_33","unstructured":"Swette, L.L., Griffith, A.E., and LaConti, A.B. (1999). Potential and Diffusion Controlled Solid Electrolyte Sensor for Continuous Measurement of Very Low Levels of Transdermal Alcohol. (5,944,661), U.S. Patent."},{"key":"ref_34","unstructured":"Marques, P.R., and McKnight, A.S. (2007). Evaluating Transdermal Alcohol Measuring Devices, Technical report."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1007\/s00213-014-3644-9","article-title":"Accounting for sex-related differences in the estimation of breath alcohol concentrations using transdermal alcohol monitoring","volume":"232","author":"Roache","year":"2015","journal-title":"Psychopharmacology"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2060","DOI":"10.1111\/acer.14172","article-title":"Temporal dynamics of transdermal alcohol concentration measured via new-generation wrist-worn biosensor","volume":"43","author":"Fairbairn","year":"2019","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1918","DOI":"10.1111\/acer.14432","article-title":"Wearable transdermal alcohol monitors: A systematic review of detection validity, and relationship between transdermal and breath alcohol concentration and influencing factors","volume":"44","author":"Wright","year":"2020","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2805","DOI":"10.1111\/add.15953","article-title":"Validating transdermal alcohol biosensors: A meta-analysis of associations between blood\/breath-based measures and transdermal alcohol sensor output","volume":"117","author":"Yu","year":"2022","journal-title":"Addiction"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"306","DOI":"10.1016\/j.snb.2018.09.082","article-title":"Skin alcohol perspiration measurements using MOX sensors","volume":"280","author":"Lawson","year":"2019","journal-title":"Sens. Actuators Chem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1016\/j.alcohol.2023.03.162","article-title":"Measurement of Transdermal Alcohol Concentration using a Wrist Worn Enzymatic Transdermal Monitor","volume":"110","author":"Riordan","year":"2023","journal-title":"Alcohol"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.alcohol.2021.01.007","article-title":"Wrist-worn alcohol biosensors: Applications and usability in behavioral research","volume":"92","author":"Wang","year":"2021","journal-title":"Alcohol"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"110699","DOI":"10.1016\/j.automatica.2022.110699","article-title":"Tracking and blind deconvolution of blood alcohol concentration from transdermal alcohol biosensor data: A population model-based LQG approach in Hilbert space","volume":"147","author":"Yao","year":"2023","journal-title":"Automatica"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"6739","DOI":"10.3934\/mbe.2021335","article-title":"Deconvolving breath alcohol concentration from biosensor measured transdermal alcohol level under uncertainty: A Bayesian approach","volume":"18","author":"Hawekotte","year":"2021","journal-title":"Math. Biosci. Eng. MBE"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1016\/j.coelec.2018.05.007","article-title":"Fuel cell-based breath-alcohol sensors: Innovation-hungry old electrochemistry","volume":"10","author":"Ozoemena","year":"2018","journal-title":"Curr. Opin. Electrochem."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1016\/j.yofte.2015.05.002","article-title":"A low cost and reliable fiber optic ethanol sensor based on nano-sized SnO2","volume":"24","author":"Sheikhi","year":"2015","journal-title":"Opt. Fiber Technol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"276","DOI":"10.1016\/j.bios.2016.12.046","article-title":"A potentiometric non-enzymatic glucose sensor using a molecularly imprinted layer bonded on a conducting polymer","volume":"91","author":"Kim","year":"2017","journal-title":"Biosens. Bioelectron."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1021\/cr068100w","article-title":"Potentiometric ion sensors","volume":"108","author":"Bobacka","year":"2008","journal-title":"Chem. Rev."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1002\/adhm.201300221","article-title":"Solution-gated graphene transistors for chemical and biological sensors","volume":"3","author":"Yan","year":"2014","journal-title":"Adv. Healthc. Mater."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.trac.2007.12.004","article-title":"Aptamer-based biosensors","volume":"27","author":"Song","year":"2008","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"180","DOI":"10.1016\/0167-7799(85)90119-2","article-title":"Immunosensors: Antibody-based biosensors","volume":"3","author":"North","year":"1985","journal-title":"Trends Biotechnol."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/j.bios.2018.03.039","article-title":"In-vitro model for assessing glucose diffusion through skin","volume":"110","author":"Ullah","year":"2018","journal-title":"Biosens. Bioelectron."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1111\/1523-1747.ep12461011","article-title":"Transcutaneous chemical collection of caffeine in normal subjects: Relationship to area under the plasma concentration-time curve and sweat production","volume":"96","author":"Conner","year":"1991","journal-title":"J. Investig. Dermatol."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"963","DOI":"10.1208\/s12249-015-0291-3","article-title":"Investigating transdermal delivery of vitamin D 3","volume":"16","author":"Alsaqr","year":"2015","journal-title":"AAPS PharmSciTech"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1093\/jat\/18.6.298","article-title":"Sweat testing for heroin, cocaine, and metabolites","volume":"18","author":"Cone","year":"1994","journal-title":"J. Anal. Toxicol."},{"key":"ref_55","first-page":"545","article-title":"The current status of sweat testing for drugs of abuse: A review","volume":"20","author":"Fucci","year":"2013","journal-title":"Curr. Med. Chem."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/S0378-5173(98)00113-6","article-title":"Skin permeability data: Anomalous results","volume":"170","author":"Degim","year":"1998","journal-title":"Int. J. Pharm."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"432","DOI":"10.1016\/j.ijpharm.2018.06.012","article-title":"Strat-M\u00ae synthetic membrane: Permeability comparison to human cadaver skin","volume":"547","author":"Haq","year":"2018","journal-title":"Int. J. Pharm."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/0003-2697(81)90442-5","article-title":"A new highly sensitive assay for breath acetaldehyde: Detection of endogenous levels in humans","volume":"114","author":"Dannecker","year":"1981","journal-title":"Anal. Biochem."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1007\/s00408-017-9979-3","article-title":"Volatile organic compounds in exhaled breath of idiopathic pulmonary fibrosis for discrimination from healthy subjects","volume":"195","author":"Yamada","year":"2017","journal-title":"Lung"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"3236","DOI":"10.1002\/jps.20896","article-title":"First-principles, structure-based transdermal transport model to evaluate lipid partition and diffusion coefficients of hydrophobic permeants solely from stratum corneum permeation experiments","volume":"96","author":"Deen","year":"2007","journal-title":"J. Pharm. Sci."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1023\/A:1015810312465","article-title":"Predicting skin permeability","volume":"9","author":"Potts","year":"1992","journal-title":"Pharm. Res."}],"container-title":["Biosensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-6374\/13\/9\/845\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:38:57Z","timestamp":1760128737000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-6374\/13\/9\/845"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,8,25]]},"references-count":61,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2023,9]]}},"alternative-id":["bios13090845"],"URL":"https:\/\/doi.org\/10.3390\/bios13090845","relation":{},"ISSN":["2079-6374"],"issn-type":[{"value":"2079-6374","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,8,25]]}}}