Discretised microfluidics for noninvasive health monitoring using sweat sensing†

Using sweat instead of blood for monitoring chemical biomarker concentrations of hospitalised patients offers several advantages for both the patients and healthcare workers. Unlike blood, sweat can be noninvasively and continuously sampled without direct involvement of a professional, and sweat contains a rich composition of biomarkers. However, patients in resting state have extremely low sweat rates and they produce correspondingly small sweat volumes, which makes sweat sensing of hospitalised patients highly challenging. We propose a unique solution that enables the use of sweat as a viable biofluid for noninvasive health monitoring, by actively transporting the sweat in a discretised manner. Our device uses electrowetting-on-dielectrics (EWOD) to create and move sweat droplets with a volume of around 1 nanolitre from a sweat gland to sensors integrated in the device. We present the first wearable device with integrated EWOD, and we show that it can collect and transport sweat on-body, while measuring sweat rate, under conditions typical for individuals at rest.