Tactile sensors, in the form of conformal and embedded devices, have attracted intense research interest because of their diverse applications, from electronic skin (E-skin) for robotics to health care monitoring systems. Much effort has been made to develop large- area and high-performance tactile sensors with good sensitivity and mechanical flexibility. MoS₂ semiconductors have recently attracted attention because of their outstanding mechanical and optical transmittance, high gauge factor, and tunable band gap. However, there is no report on multi-cell devices for practical applications that transcend the fabrication of a single cell. In this talk, I present an ultrathin conformal, MoS₂-based tactile sensing array covering an area of 2.2 cm ´ 2.2 cm. We integrated the sensor with a graphene electrode and interconnect to achieve good mechanical flexibility and optical transmittance in the visible color range (Figure 1). This sensor shows high sensitivity, good uniformity, and linearity even after 1000 loading cycles. In addition, it provides excellent mechanical flexibility over strain of 1.98% and better than 80% transparency.

Figure 1. MoS₂ tactile sensor transferred on the fingertip. a-b) Optical and SEM images of the MoS₂ tactile sensor on a fingertip. c) Colorized SEM images of the MoS₂ strain gauge (left, yellow) and graphene electrode (right, blue). d) Pressure map detected by the MoS₂ tactile sensor from contact with pens of different diameters (7 and 5 mm). e) Calculated crosstalk isolation of the MoS₂ sensor array with different pen-tip sizes (D : 7,5 and 2 mm).