Nanshu Lu1

1, University of Texas at Austin, Austin, Texas, United States

Bio-tissues are soft, curvilinear and dynamic whereas wafer-based electronics are hard, planar, and fragile. Such mismatch fundamentally impedes their integration with each other. As an atomically thin, optically transparent, mechanically robust, electrically conductive, and chemically inert material, graphene is an ideal material for skin-mounted soft biometric sensors. We have invented a cost- and time-effective “wet transfer, dry patterning” process for the freeform manufacture of graphene e-tattoos (GETs) [1]. Our GET has a total thickness of less than 500 nm, an optical transparency of ~85%, and a stretchability of more than 40%. Tensile fracture of PMMA-supported graphene has been experimentally investigated and compared with PMMA-supported gold thin film [2]. GET can be directly laminated on human skin exactly like a temporary transfer tattoo and can fully conform to the microscopic morphology of the skin surface via just van der Waals forces. Analytical models are developed to predict GET-skin conformability even under skin deformation [3]. The open mesh structure of GET makes it breathable and its stiffness negligible. As a dry electrode, GET-skin interface impedance is found to be as low as medically used Ag/AgCl gel electrodes. GET has been successfully applied to measure electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), skin temperature, and skin hydration. When applied around human eyes, imperceptible GET electrooculogram (EOG) sensors can capture eye movement with an angular resolution of 4 degrees, which can be used to wirelessly control a quadcopter in real-time [4].

[1] S. K. Ameri, R. Ho, H. W. Jang, L. Tao, Y. H. Wang, L. Wang, D. M. Schnyer, D. Akinwande, N. Lu, Acs Nano 2017, 11, 7634-7641.
[2] H. Jang, Z. Dai, S. K. Ameri, N. Lu, To be submitted 2017.
[3] L. Wang, S. Qiao, S. Kabiri Ameri, H. Jeong, N. Lu, Journal of Applied Mechanics 2017, 84, 111003.
[4] S. K. Ameri, M. Kim, I. A. Kuang, W. K. Perera, M. Alshiekh, H. Jeong, U. Topcu, D. Akinwande, N. Lu, submitted 2017.