Contact Pressure Level Indication Using Stepped Output Tactile Sensors

Abstract

In this article, we report on a novel diaphragm-type tactile pressure sensor that produces stepwise output currents depending on varying low contact pressures. When contact pressures are applied to the stepped output tactile sensor (SOTS), the sensor’s suspended diaphragm makes contact with the substrate, which completes a circuit by connecting resistive current paths. Then the contact area, and therefore the number of current paths, would determine the stepped output current produced. This mechanism allows SOTS to have high signal-to-noise ratio (>20 dB) in the 3–500 Hz frequency range at contact pressures below 15 kPa. Moreover, since the sensor’s operation does not depend on a material’s pressure-dependent electrical properties, the SOTS is able to demonstrate high reproducibility and reliability. By forming a 4 × 4 array of SOTS with a surface bump structure, we demonstrated shear sensing as well as surface (1 × 1 cm2) pressure mapping capabilities.

Highly Sensitive Tactile Shear Sensor Using Spatially Digitized Contact Electrodes

“…If two shear sensors were integrated perpendicularly to each other, shear from different in-plane directions will be detectable. For vertical pressure detection, we could integrate a stepped output tactile sensor [26] that we have developed previously, which utilizes a digitized CE configuration similar to the shear sensor. Therefore, one pressure sensor integrated with two perpendicular tactile shear sensors will be able to detect tactile forces applied from various directions.…”

“…Figure 1a shows a schematic diagram of the tactile shear sensor. Its operational concept is similar to the stepped output tactile sensors we have reported previously [26], except that it has a central spacer that supports the top diaphragm directly under a ridge structure on its surface. The sensor consists mainly of two parts, the upper diaphragm with a ridge structure and the bottom substrate.…”

Tactile Interaction Sensor with Millimeter Sensing Acuity

“…Depending on the pressure, the number of CEs shorted with the ground electrode is determined, and a proportional current level is generated. In comparison to our previous sensor [ 29 ], the base sensor structure having a conducting diaphragm and CEs is similar. However, in this study we utilized graphene, not metallic thin-film, as the electrode under the diaphragm to improve the operating mechanical reliability on repetitive diaphragm deflection.…”

“…This TIS was designed based on our previous reports utilizing mechanical switches under diaphragm deflection [ 29 , 30 ]. To simultaneously detect shear direction and pressure distribution at millimeter scales, we integrated four pressure sensor units and three shear sensor units on TIS within a 3 × 3 mm area.…”

Biomimetic Tactile Sensors with Bilayer Fingerprint Ridges Demonstrating Texture Recognition

“…After the PDMS was cured, the fabricated SKIN #2 was peeled off from the master. The PET film for SKIN #2 was etched by CF 4 physical plasma to form nanobrush structures, which promoted adhesion with PDMS by increasing the contact surface area [27,28]. For SKIN #3, a 50-μm-thick SU-8 layer and 50-μm-thick PDMS were coated on the oxidized silicon substrate.…”