Interpersonal Touch Sensing Devices Using Inter-Body Area Network

Interpersonal touch interactions are an essential social behavior for physical and mental health. We previously developed a smart bracelet-type device, called EnhancedTouch, which quantitatively measures interpersonal hand-to-hand touch interactions by actively transmitting and receiving a modulated electrical current through the human hands. However, it remains unclear how the current will flow between devices. Such ambiguity is due to the fact that a general instrument such as an oscilloscope needs to be connected to the ground of the device, which enhances a coupled ground reference and results in a stable performance compared to a device operating under a more realistic situation, i.e., a wireless wearable device. This paper presents the design guidelines of such devices. We introduce the details of design and the implementation of a bracelet device, which is a revised version of EnhancedTouch. A pair of devices is used to evaluate the signal transmission by means of the signal-to-noise ratio (SNR) with a ground-free wireless measurement system. An experiment with four conditions were conducted to study the following effects: 1) the distance between devices and the contact area of the hands, 2) the distance between users, 3) the height from the floor to the devices, and 4) the configuration of electrodes on the signal transmission. The results indicate that either a shorter distance between devices or a larger contact area of the hands results in a relatively high SNR. In addition, the results also suggest that the configuration of electrodes significantly affects the SNR.