1:30 PM - *SB06.05.01
Wireless Graphene E-Tattoos for Long-Term Mental Stress Monitoring
The University of Texas at Austin1
Mental stress negatively impacts more than 77% population in our modern societies. Electrodermal activity (EDA), a.k.a. galvanic skin response (GSR), is an emotion-induced skin conductance change due to sweat gland activity, which has been widely used as a quantitative index of mental stress levels for decades. Palm has the highest density of eccrine sweat glands which are filled up under psychological stimuli, such as mental stress, primarily. However, state-of-the-art EDA monitors suffer from limitations such as obstructiveness, short-term wearability, motion artifacts, etc. My group has previously engineered mechanically and optically imperceptible wearable sensors named graphene e-tattoos (GET).[1-3] Herein, we introduce a wireless, long-term wearable (e.g. 24 hours), high-fidelity palm EDA sensor based on 150-nm-thick GET. The ultrathin GET can fully conform to the finest texture of human skin, resulting in an interface impedance even lower than that of the wet Ag/AgCl gel electrodes. GET is laminated on the palm and needs to extend to the wrist to connect to a wristwatch which provides data acquisition, storage, and wireless transmission. The orders-of-magnitude mismatch of stiffness and thickness between the GET and the wristwatch poses a significant challenge for the electrical connection in between. We propose a simple yet effective solution named “heterogenous serpentine ribbon (HSR).” Compared with contacts between straight GET and metal ribbons, HSR offers a ten-fold strain reduction. We have successfully applied such GET-watch-based wearable EDA sensor for long-term, continuous, and ambulatory EDA sensing during our daily activities as well as during sleep. The HSR could be a generic solution to robustly connect any ultrathin and ultrasoft e-tattoos to smartwatches or rigid PCBs, which could significantly expand the sensing modalities of future smartwatches and other wearable devices.
1 Ameri, S.K., Ho, R., Jang, H.W., Tao, L., Wang, Y.H., Wang, L., Schnyer, D.M., Akinwande, D., and Lu, N.: ‘Graphene Electronic Tattoo Sensors’, Acs Nano, 2017, 11, (8), pp. 7634-7641
2 Ameri, S.K., Kim, M., Kuang, I.A., Perera, W.K., Alshiekh, M., Jeong, H., Topcu, U., Akinwande, D., and Lu, N.: ‘Imperceptible Electrooculography Graphene Sensor System for Human-Robot Interface ’, npj 2D Materials and Applications, 2018, 2, pp. 19
3 Kireev, D., Ameri, S.K., Nederveld, A., Kampfe, J., Jang, H., Lu, N., and Akinwande, D.: ‘Fabrication, characterization and applications of graphene electronic tattoos’, Nature Protocols, 2021, 16, (5), pp. 2395-2417