Simultaneous Monitoring of Sweat and Interstitial Fluid Using a Single Wearable Biosensor Platform

Abstract

The development of wearable biosensors for continuous noninvasive monitoring of target biomarkers is limited to assays of a single sampled biofluid. An example of simultaneous noninvasive sampling and analysis of two different biofluids using a single wearable epidermal platform is demonstrated here. The concept is successfully realized through sweat stimulation (via transdermal pilocarpine delivery) at an anode, alongside extraction of interstitial fluid (ISF) at a cathode. The system thus allows on‐demand, controlled sampling of the two epidermal biofluids at the same time, at two physically separate locations (on the same flexible platform) containing different electrochemical biosensors for monitoring the corresponding biomarkers. Such a dual biofluid sampling and analysis concept is implemented using a cost‐effective screen‐printing technique with body‐compliant temporary tattoo materials and conformal wireless readout circuits to enable real‐time measurement of biomarkers in the sampled epidermal biofluids. The performance of the developed wearable device is demonstrated by measuring sweat‐alcohol and ISF‐glucose in human subjects consuming food and alcoholic drinks. The different compositions of sweat and ISF with good correlations of their chemical constituents to their blood levels make the developed platform extremely attractive for enhancing the power and scope of next‐generation noninvasive epidermal biosensing systems.

Application of Microfluidics in Wearable Devices

“…In wearable devices for body fluid monitoring, samples, such as sweat, interstitial fluid, saliva, and tears, usually need to be collected and guided to reach reservoirs . The smooth and efficient collection of samples is the first step in the successful operation of devices.…”

“…C) Schematic illustration and operation principle of microfluidic device for simultaneous noninvasive sampling and monitoring of sweat and interstitial fluid. Reproduced with permission . Copyright 2018, The Author(s).…”

High‐Performance Flexible Bioelectrocatalysis Bioassay System Based on a Triphase Interface

“…Flexible devices have attracted extensive research interest in the fields of physiological monitoring, intelligent display, energy collection, and storage . Flexible biosensors based on individual's physiological biomarkers have recently been fabricated that are able to provide insight into the user's health state at a molecular level as well as diabetic monitoring . In the presence of O 2 , almost all oxidases will catalyze (oxidize) their substrates (analytes) producing H 2 O 2 , the cathodic measurement of which is an ideal approach for analyte level quantification .…”

Wearable Enzymatic Alcohol Biosensor

“…Continuous alcohol sensors have received growing interest from the research community [5][6][7][8][9][10][11][12][13][14], but commercial realizations thus far have involved trade-offs in performance [15,16]. The only two commercialized platforms (SCRAM and WrisTAS) use platinum fuel cells.…”