Precise and efficient release of pilocarpine for sweat wearables

The first step in wearable sweat sensing is to controllably acquire clean sweat within a limited space. Although some drug-induced methods such as iontophoresis can obtain clean sweat, there are still unsolved problems such as uncontrollable drug release, high operational current density, and low integration of modules due to the separation areas of sweat secretion and sweat delivery. In this study, we propose a novel method for the controlled release of sweat-inducing drugs for wearable sweat sensors. A kind of electro-responsive screen-printed electrode has been designed, which consists of a hybrid layer composed of 3,4-Ethylenedioxythiophene, pilocarpine nitrate, and nadroparin calcium and an electrowetting layer of polymerized 3-methylthiophene. This efficient electrode can achieve a controllable release density of up to 9.395 μg·cm^–2 for sweat-inducing pilocarpine within 10 minutes and operates at microampere levels. Furthermore, we utilized the voltage drift of Ag/AgCl electrode at varying chloride ion concentrations to achieve an estimation of chloride level in sweat for possible cystic fibrosis screening. The electrically controlled drug release, electrowetting, and electrochemical detection were integrated into a single three-electrode system first. This study is expected to promote the development of miniaturized, integrated, and non-invasive wearable biosensors for sweat monitoring.