Mechanoreceptors in a fingertip convert external tactile stimulations into electrical signals, which are transmitted by the nervous system through synaptic transmitters and then perceived by the brain with high accuracy and reliability. Inspired by the human synapse system, this paper reports a robust tactile sensing system consisting of a remote touch tip and a magnetic synapse. External pressure on the remote touch tip is transferred in the form of air pressure to the magnetic synapse, where its variation is converted into electrical signals. The developed system has high sensitivity and a wide dynamic range. The remote sensing system demonstrated tactile capabilities over wide pressure range with a minimum detectable pressure of 6 Pa. In addition, it could measure tactile stimulation up to 1,000 Hz without distortion and hysteresis, owing to the separation of the touching and sensing parts. The excellent performance of the system in terms of surface texture discrimination, heartbeat measurement from the human wrist, and satisfactory detection quality in water indicates that it has considerable potential for various mechanosensory applications in different environments.

High sensitive flexible and wearable devices which can detect delicate touches have attracted considerable attentions from researchers for various promising applications. This research was aimed at enhancing the sensitivity of a MWCNT/PDMS piezoresistive tactile sensor through modification of its surface texture in the form of micropillars on MWCNT/PDMS film and subsequent low energy Ar+ ion beam treatment of the micropillars. The introduction of straight micropillars on the MWCNT/PDMS surface increased the sensitivity under gentle touch. Low energy ion beam treatment was performed to induce a stiff layer on the exposed surface of the micropillar structured MWCNT/PDMS film. The low energy ion bombardment stabilized the electrical properties of the MWCNT/PDMS surface and tuned the curvature of micropillars according to the treatment conditions. The straight micropillars which were treated by Ar+ ion with an incident angle of 0° demonstrated the enhanced sensitivity under normal pressure and the curved micropillars which were treated with Ar+ ion with an incident angle of 60° differentiated the direction of an applied shear pressure. The ion beam treatment on micropillar structured MWCNT/PDMS tactile sensors can thus be applied to reliable sensing under gentle touch with directional discrimination.

In order to realize a transition from conventional to stretchable electronics, it is necessary to make a universal stretchable circuit board in which passive/active components can be robustly integrated. We developed a stretchable printed circuit board (s-PCB) platform that enables easy and reliable integration of various electronic components by utilizing a modulus-gradient polymeric substrate, liquid metal amalgam (LMA) circuit traces, and Ag nanowire (AgNW) contact pads. Due to the LMA–AgNW biphasic structure of interconnection, the LMA is hermetically sealed by a homogeneous interface, realizing complete leak-free characteristics. Furthermore, integration reliability is successfully achieved by local strain control of the stretchable substrate with a selective glass fiber reinforcement (GFR). A strain localization derived by GFR makes almost 50,000% of strain difference within the board, and the amount of deformation applied to the constituent elements can be engineered. We finally demonstrated that the proposed integrated platform can be utilized as a universal s-PCB capable of integrating rigid/conventional electronic components and soft material-based functional elements with negligible signal distortion under various mechanical deformations.

Durability and multifunctionality are very important factors for human skinlike tactile sensors for measuring physical stimuli if they provide reasonable pressure measurement range and sensitivity. Here, we propose a step tactile sensor with a simple processing unit, showing high repeatability and mechanical stability without drifting caused by thermal and geometrical noise. The proposed sensor, similar to a switch mechanism, detects the applied pressure discretely and has a wide pressure range of 2 kPa to 1.2 MPa according to its geometry. The developed tactile sensor can be designed and fabricated in various morphologies to detect a wide range of tactile stimuli, which help in customizing the sensor as per user demand for practical applications such as a prosthesis arm or hand. It is also easy to extend the sensor size to cover a large area owing to the simple fabrication process by using a 3D printer. Furthermore, with the addition of a flexible exterior layer of leuco dyes and the polydimethylsiloxane mixture, the color of a step tactile sensor not only resembles that of human skin color but also changes its color depending on the temperature changes as human skin does. Thus, the function of a pressure and temperature indicator in a flexible step sensor finds practical applications in various fields, including but not limited to prosthetic applications for the customized and comfortable usage.