Flexible Capacitive Tactile Sensors Based on Carbon Nanotube Thin Films

Abstract

Carbon nanotubes (CNTs) are an interesting material for mechanically flexible electronic devices. The possibility to fabricate CNT thin films from solution by scalable coating and printing techniques has paved the way for large-area and low-cost sensor applications. In this paper, we demonstrate mechanically flexible capacitive tactile sensors utilizing spray deposited CNT thin-films and microstructured PDMS spacers. The capacitance is monitored during sensor operation and forces smaller than 10 mN could be detected and changes of up to 20% are achieved for 1 N of applied force. Sensor response can be tailored through an appropriate design of the dielectric spacer. The long-term operational stability of the proposed sensors is demonstrated. Further, a theoretical model is proposed and fitted to experimental data, providing a powerful tool to facilitate the design process.

Integration of a Thin Film PDMS-Based Capacitive Sensor for Tactile Sensing in an Electronic Skin

“…As can be seen in Figure 5(b), the sensor goes back to its initial capacitance value if there is no force applied with an error less than 3% at the different force steps applied. If we compare this response with the one reported by Cagatay et al [25] for a PDMS film of about 110 m and pillar of about 30 m, we observe similar capacitance values under no force. The sensitivity is about 10% lower in the sensor described here, but the fabrication procedure and the integration on a final system are much easier.…”

“…The characterization of the force was performed as in [25]. A voice coil actuator VM2836-180 from Geeplus (Beckenham, UK) was used to generate the normal force .…”

“…A work from Woo et al presented a capacitive force sensor array based on a micro-patterned film of a conductive CNT-doped PDMS produced by a combination of soft-lithographic replication and contact printing [24]. Flexible capacitive tactile sensors with microstructured PDMS as dielectric material and utilizing spray deposited CNT thin films as transparent conductors on polyimide substrates have been reported [25]. The sensor can detect forces below 10 mN and a variation in capacitance of up to 20% for 1 N of applied force can be achieved with good long-term reliability.…”

P‐138: A High Sensitive Resistive Pressure Sensor with NH4HCO3‐induced Porous Structure Active Layer

“…Pressure sensor, monitoring the external force and deformation, has attracted people's attention in wearable devices and robotics. Generally, pressure sensors can detect the deformation and motions based on the piezoelectricity [1][2], capacitance [4][5][6][7][8] and resistance [9][10][11][12][13][14][15].The piezoelectric sensor shows high sensitivity and fast response time but are susceptible to external electric field and temperature. The capacitance-type sensor shows high sensitivity and has the potential in transparent pressure sensors while it is sensitive to strong electric field.…”

Development of a flexible and stretchable tactile sensor array with two different structures for robotic hand application

“…Many mechanisms have been utilized to make pressure sensors such as resistive, 14,15 piezoresistive, 16 piezoelectric 17,18 and capacitive mechanisms. 19,20 The capacitive sensors have higher sensitivity and relatively simpler structures, and they can be integrated with other exible electronics or CMOS devices. Recent work has also demonstrated that a exible stress sensor array could have very high sensitivity in the small stress range from 0 to 30 kPa.…”