A flexible graphene touch sensor in the general human touch range

Abstract

We present a transparent touch sensor based on single layers of graphene that works under a gentle touch. Using the flexible characteristics of graphene, a touching event and a vertical force are measured by a change in the channel conductance. In contrast to the previous graphene gauge sensors, this is an alternative scheme that responds to a vertical force using the contacting properties of two isolated and patterned single graphene layers. This sensor responded to pressures ranging from 1 to 14 kPa, corresponding to the lowest human perception. In addition, we outline the processing methods for handling single layers of graphene for the integration of devices on transparent and flexible substrates.

Flexible, Transparent, Sensitive, and Crosstalk‐Free Capacitive Tactile Sensor Array Based on Graphene Electrodes and Air Dielectric

“…Figure 4d shows the changes in capacitance of the 36 cells against two different pressures (6 and 12 kPa) and locations (C 25 www.advelectronicmat.de in Figure 4d). When either pressure was applied on the C 25 and C 43 area, the capacitance of these cells increased by 33.84% and 76.52%, respectively.…”

“…Given its high fracture strain (>20%), low sheet resistance (≈300 Ω sq −1 ), and high transmittance (≈97.5%), [22] many graphene-based tactile sensors have been reported thus far, but most of these utilized graphene as a piezoresistive or resistive sensing element. [23][24][25] Although previous works have shown high performance with sufficient flexibility and transparency, these devices still have the limitations of conventional piezoresistive and resistive tactile sensors. Thus, the development of a tactile sensor that not only overcomes the limitations of existing devices but also provides improved performance is highly desired.…”

Ultraflexible Tactile Piezoelectric Sensor Based on Low-Temperature Polycrystalline Silicon Thin-Film Transistor Technology

“…Especially for the sense of touch, the integration of robust, light and bendable pressure and temperature sensors is a key aspect for the definition of a bio-inspired skin able to reproduce the human tactile experience in terms of the range of forces, frequencies of vibration, sensor response time, spatial resolution, etc. In recent years, a variety of new touch sensing technologies using different materials and transduction methods [3]- [5] have been introduced, giving rise to a series of tremendously improved designs of electronic skins suitable for humanoid robots. Unfortunately, most of these devices are still quite large and are fabricated on rigid substrates, so they cannot be completely integrated onto specific areas, such as robot fingertips, where a large number of sensors are required on a limited and non-planar surface.…”

Graphene electronic fibres with touch-sensing and light-emitting functionalities for smart textiles

“…The various on/off intervals in c, d, e, f, h are due to the difference in the intensity and duration of the user's finger touching the device used in the measurement, within the range of commercial devices and rival with the best values in the literature. [27][28][29][30] In contrast to miniaturised conventional CMOS electronics that are mounted on flexible and textile substrtes, 35 smart textiles attained by intertwined graphene fibres allow advanced detection schemes that can be readily implemented when complex functions such as simultaneous multi-touch features are required ( Supplementary Video 1).…”

“…[24][25][26] Similarly, several reports of touch-sensors based on different electrodes including graphene have also been published, but most of them have rise and fall times in the order of seconds. [27][28][29][30] To address the device fabrication compatibility with scale-up manufacturing, we developed a roll-to-roll-compatible patterning technique, enabling the integration of graphene circuits into fabrics. By creating woven arrays from such fibres, we demonstrate pixels with different sizes that can be integrated in future textile displays and devices for position sensitive measurements.…”