(495c) Soft Materials for Exertion-Free Epidermal Healthcare Monitoring

Over the past few years, the interest towards accessing health information directly from the skin has witnessed some monumental developments. Such interests have further grown since blood can be accessed only through invasive (fingerpick) means. This has led researchers to venture into other alternative non-invasive biofluid options such as interstitial fluid (ISF), saliva, tears, and sweat for knowing the health status of individuals, amongst which ISF, saliva and tears remain difficult to sample and manage long-term. Sweat on the other hand is easy to access since it can be generated on-skin easily via simple physical exertion.^[1] Most sweat biosensors rely on physical exertion for their performance and remain inoperable on sedentary subjects and low humidity conditions. In this talk, I will be discussing about our novel principles for the design of flexible and wearable patches, which are capable of extracting sweat under both resting and actively perspiring conditions using osmotic pressure difference for pumping, and evaporation for liquid disposal.^[2] We use soft and simple materials such as hydrogels and a paper microfluidic channel to perform this task. The osmotic pressure difference builds up with a high solute containing hydrogel, which stays interfaced directly to the skin for sweat extraction.^[3] The extracted sweat gets sampled on a paper microfluidic conduit with a site for evaporation at the end (evaporation pd). In-vitro studies confirmed glucose treated hydrogels to facilitate the highest analyte accumulation on the pad, while on-body trials showed the potential to extract sweat and analyze it for lactate under rested conditions for two hours.^[4] Apart from this, I will be also discussing about our diffusion based sweat sampling technique which can also deliver biomarker information under resting conditions. This technique can be executed again with a soft and porous hydrogel on the fingertip (high sweat gland density), allowing discrete, touch-based, and painless monitoring from sweat. We have tested this prototype for estimating sweat ketone levels due to its relations with diabetes.^[5] Overall, my PhD and postdoc research till date has introduced hydrogels as a potential medium for sweat sampling under sedentary conditions, eventually making possible to access health information (similar to blood) without physical exertion. As a faculty member, I envision addressing the current limitations of non-invasive biofluid sampling, transport, management, and targeting unconventional biomarkers. My training as a chemical engineer on health-based research will allow my research group to work at the intersection of device fabrication, sensor development, polymer chemistry, nanomaterials, microfluidics, electrochemistry, and in-vivo (on-body and clinical) validation. My research would also have the scope of seeking collaborations from electrical engineers (for electronic integration), data scientists (for correlation studies), and medical professionals (for clinical trials), making it highly interdisciplinary by nature. Overall, I intend on training and developing the next generation of chemical engineers for health-based research.

[1] T. Saha, R. Del Caño, E. la De Paz, S. S. Sandhu, J. Wang, Small 2022, 2206064, 2206064.

[2] T. Shay, T. Saha, M. D. Dickey, O. D. Velev, Biomicrofluidics 2020, 14, 034112.

[3] T. Saha, J. Fang, S. Mukherjee, M. D. Dickey, O. D. Velev, ACS Appl. Mater. Interfaces 2021, 13, 8071.

[4] T. Saha, T. Songkakul, C. T. Knisely, M. A. Yokus, M. A. Daniele, M. D. Dickey, A. Bozkurt, O. D. Velev, ACS Sensors 2022, 7, 2037.

[5] J. Moon, R. Del Caño, C. Moonla, K. Sakdaphetsiri, T. Saha, L. Francine Mendes, L. Yin, A. Chang, S. Seker, J. Wang, ACS Sensors 2022, 7, 3973.