Wearable Organic Electrochemical Transistor Patch for Multiplexed Sensing of Calcium and Ammonium Ions from Human Perspiration

Abstract

Wearable health monitoring has garnered considerable interest from the healthcare industry as an evolutionary alternative to standard practices with the ability to provide rapid, off‐site diagnosis and patient‐monitoring. In particular, sweat‐based wearable biosensors offer a noninvasive route to continuously monitor a variety of biomarkers for a range of physiological conditions. Both the accessibility and wealth of information of sweat make it an ideal target for noninvasive devices that can aid in early diagnosis of disease or to monitor athletic performance. Here, the integration of ammonium (NH4+) and calcium (Ca2+) ion‐selective membranes with a poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)‐based (PEDOT:PSS) organic electrochemical transistor (OECT) for multiplexed sensing of NH4+ and Ca2+ in sweat with high sensitivity and selectivity is reported for the first time. The presented wearable sweat sensor is designed by combining a flexible and stretchable styrene‐ethylene‐butene‐styrene substrate with a laser‐patterned microcapillary channel array for direct sweat acquisition and delivery to the ion‐selective OECT. The resulting dermal sensor exhibits a wide working range between 0.01 × 10−3 and 100 × 10−3 m, well within the physiological levels of NH4+ and Ca2+ in sweat. The integrated devices are successfully implemented with both ex situ measurements and on human subjects with real‐time analysis using a wearable sensor assembly.

Organic Bioelectronics: Using Highly Conjugated Polymers to Interface with Biomolecules, Cells, and Tissues in the Human Body

“…Ion‐sensitive devices can also be fabricated by incorporating ion selective membranes onto the conjugated polymer layer. [ 176,195,196 ]…”

“…have demonstrated how ion‐selective OECTs can be used to monitor ammonium and calcium ions from the sweat of volunteers wearing a forearm patch ( Figure ). [ 195 ]…”

Organic materials and devices for brain-inspired computing: From artificial implementation to biophysical realism

“…By engineering the chemical structure of the active materials (i.e., channel or gate material) OECTs are capable of ionic signal discrimination in sensing, for instance selectivity of Na + over K + ions, or selectivity of Ca + , NH 4 + ions. [119][120][121] Selective detection of neurotransmitters such as dopamine, in the presence of other interfering chemical compounds is also possible with OECTs. 122,123 The above examples emphasize the potential of OECTs to emulate the selectivity of ionic channels in processing (voltage-or neurotransmitter-gated channels in biological membranes), or to decouple the variety of information carriers that are present in the biological environment.…”

Printed Organic Transistor-based Biosensors for Non-invasive Sweat Analysis

“…In addition to these transistor-based biosensors, we included a recently developed electrochemical transistor that uses organic conducting polymers-such as poly(3,4-ethylenedioxythio phene): poly(styrenesulfonate) (PEDOT:PSS)-as a semi conductor layer in our summary shown in Table 1. [46][47][48][49][50][51] In this biosensor, with generally electrolyte-gate configuration, gate voltage against a gate electrode is applied to a conducting polymerbased semiconductor layer, through a sample solution, in order to control the doping level of the conducting polymer. A bioreceptor immobilized on the conducting polymer can induce change in the interfacial potential of the electric double layer through a biorecognition reaction.…”