Modeling Capacitive Sweat Rate Sensor

Coauthor of Paper Published in Advanced Intelligent SystemsKhan Lab, USC

Supervisor
Professor Yasser Khan
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Publications

Abstract

Sweat rate measures key physiological states such as hydration levels and heat tolerance. Incorporating wearable technology with sweat rate sensors allows individuals to conveniently monitor their health, optimize workouts, and enhance occupational safety. However, challenges persist in such integration techniques, including intricate manufacturing, nonlinear responses to changes in sweat rates, and errors from the intermediate measurement of the distance sweat travels in the sensor. To address these issues, we present a comprehensive wearable platform that includes a fully printed, flexible sensor patch, readout electronics, and a mobile app for continuous, real-time monitoring of sweat rate. We fabricate a sensor patch with an area of 700 mm² and a weight of 380 mg by utilizing direct 3D printing and scalable microfluidic fabrication. The microfluidic channels are 850 μm wide and 164 μm thick, with serpentine electrodes measuring sweat rate using capacitance…

My Contribution

I helped to visualize and communicate the design of our wearable capacitive sweat sensor by creating detailed 3D models of the capacitive sweat rate sensor in Fusion 360.

Effective communication is one of the most crucial aspects of any advancements in science, and my hope is that I could enhance the understanding and appreciation of our lab’s capacitive sweat sensor. Through detailed CAD models, I highlighted the sensor’s structural layers, design features, material composition, and functionality. Here are some of the published designs:

Exploded 3D model of the sweat rate sensor showing three stacked layers.
Three layers of the sweat rate sensor. Bottom layer - the encapsulated Ag electrodes on a flexible polyimide substrate. Middle layer - the patterned microfluidics channel to direct the sweat. Top layer - microfluidics cover. Both the substrate and microfluidic layers are hydrophilic, so they generate a capillary force that directs sweat into the dielectric channel.
3D model of two parallel electrodes under a channel partly filled with sweat.
Capacitive system for the analytical modeling of the sweat rate sensor. Capacitance is formed by the sweat and the air within the dielectric channel. Dielectric encapsulation and the two parallel metal electrodes are shown.
3D model of a substrate with two parallel serpentine silver electrodes.
Fabrication process - direct 3D writing of two parallel Ag electrodes.
3D model of the electrodes covered by a dielectric encapsulation layer.
Fabrication process - direct 3D writing of dielectric encapsulation.
3D model of double-sided microfluidic tape placed over the encapsulated electrodes.
Fabrication process - assembly of a double-sided microfluidic tape, patterned by using a desktop cutter machine, with the already encapsulated Ag electrodes.
3D model of the finished sensor with its microfluidic cover attached.
Fabrication process - assembly of a microfluidic cover, patterned by using the same desktop cutter machine, concluding the sensor fabrication.
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