Flexible Touch Sensors Made of Two Layers of Printed Conductive Flexible Adhesives

Abstract

Touch sensors are crucial in controlling robotic manipulation when a robot interacts with environmental objects. In this study, multilayer flexible touch sensors in the form of an array were developed. The sensors use ink-type conductive flexible adhesives as electrodes which were printed on polyethylene terephthalate (PET) films in a parallel equidistance stripe pattern. Between the two printed layers, a double-sided adhesive film was used to combine each layer and was perforated at the junctions of the top and bottom electrodes with different-sized circles. These holes represent switching mechanisms between the top and bottom electrodes, and their sizes make the sensor respond to different levels of external pressure. We showed the durability of the fabricated sensor with 1 mm diameter holes by repeated experiments of exerting normal pressure ranging from 0 to 159.15 kPa for 1000 cycles. In case of 1 mm diameter holes, the state of each sensor node was reliably determined by the threshold pressures of 127.3 kPa for increasing pressure and 111.4 kPa for decreasing pressure. On the other hand, decreasing the hole size from 3 to 0.5 mm caused an increase in the threshold pressure from 1.41 to 214 kPa. The relation between the hole size and the threshold pressure was analyzed by a mechanical model. The sensor performance was also verified on curved surfaces up to 60 mm radius of curvatures. Additionally, we fabricated a sensor with three levels of sensitivity with a conventional method which was a thermal evaporation to show the extendibility of the idea.

A flexible and low-cost tactile sensor for robotic applications

“…The accuracy of the sensor is high, however it is unclear if higher spatial resolutions can be reached easily. Another approach is presented in [24], based on conductive ink on a PET film. While this sensor is easy to manufacture, only discrete pressure values are detected.…”

Customizable, Flexible Pressure, and Temperature Step Sensors with Human Skinlike Color

“…The relationship of pressure response and the ratio of the length ( w / d ) have been analyzed in a previous study. 42 Figure 4a describes the pressure response of a single cell with three thicknesses of the top electrode layer according to increasing area ratio ( w 2 / d 2 ) of the inverse bumper and hole areas. The area of the inverse bumper is fixed to 4 mm 2 , the hole area of the intermediate layer is changed gradually from 0.16 to 8.41 mm 2 , and finally, the ratio is varied from 25.0 to 0.48.…”

Properties of Tactile Sensors Based on Resistive Ink and the Dimension of Electrodes

“…In the previous versions of the device PLANTOGRAF -that measure the pressure distribution on a surface -conductive elastomer Yokohama Rubber CS57-7RSC was initially used; this material was commonly used in the production of tactile sensors [1][2][3][4][5][6]; different polymers and their properties are nearly described in [7][8][9][10]. However, this material with a thickness of 0,5 mm exhibits a relatively large hysteresis in the range of some percent, which prevents the measuring of the absolute pressure acting on the electrodes' system.…”