(93g) Towards a Wearable Biochemical Sensing Platform: Hydrogel Enabled Osmotic Sweat Pumping for Microfluidics

Authors: 
Shay, T., NC State University
Dickey, M. D., North Carolina State University
Velev, O. D., North Carolina State University
The use of wearable devices in healthcare can greatly benefit from the development of new microfluidic sampling methods for sensing biomarkers in sweat. Therefore, we aim to develop a wearable platform for osmotic non-invasive microfluidic sweat sampling. By combining hydrogels with a microfluidic network, we seek to create a soft matter platform that is non-invasive and capable of pumping sweat from the body with no power requirement. The osmotic properties of hydrogels can draw fluid passively through a membrane and deliver it to a microfluidic network for biochemical sensing purposes. To demonstrate this concept, a microfluidic device was combined with thin biocompatible hydrogel discs equilibrated in saline or glycerol. The hydrogel interfaces with a water-permeable membrane, mimicking skin permeability. The high concentration of solute in the hydrogel creates an osmotic pressure difference across the membrane driving fluid flow through the membrane and into the microfluidic device. The release of this solute from the hydrogel autonomously pumps the fluid into an adjacent microfluidic channel. The osmotic strength of the hydrogel and its interfacial contact area with the membrane controls the flowrate. Continuous withdrawal of the fluid dilutes the concentration of solute in the hydrogel, which decreases the flowrate over time. Initial testing has shown that this sensing platform can pump biologically relevant and accurate levels of glucose across the membrane and through a microchannel to a reservoir interfacing a glucose sensor. Sensors and electrodes can be implemented into this microfluidic platform to test for other bioanalytes in sweat. This work represents an important step toward non-invasive sensing of sweat.