Rational Design of Ultrasensitive Pressure Sensors by Tailoring Microscopic Features

Abstract

Wearable sensors are increasingly used in a wide range of applications such as tactile sensors and artificial skins for soft robotics, monitoring human motions for wellbeing and sports performance, and pressure control of compression garments for wound healing. In this work, we present an ultrasensitive resistive pressure sensor based on conductive polydimethylsiloxane (PDMS) thin films with different microstructures. These microscopic features include micro-pyramids, micro-semi-spheres, and micro-semi-cylinders which are created by soft lithography replication of 3D printing templates. To enable piezoresistivity, a thin layer of carbon nanofibers (CNFs) is spray-coated on the textured PDMS film. Pressure sensors are created by pairing the resultant conductive PDMS thin film with a conductive electrode made of coating a poly(ethyleneterephthalate) film with indium tin oxide. The resistance changes of the three microstructure designs under compression loading show that the micro-semi-cylinder-based sensor has the highest sensitivity of -3.6 kPa -1 . Finite element modelling reveals that among the three designs, the micro-semi-cylinders show the largest change in contact area under the same pressure, consistent with the experimental results that the largest resistance change under the same pressure. This sensor is capable of detecting pressure as low as 1.0 Pa. All of the three designs show good reproducibility and excellent cyclic stability. This 3D printing technology is a promising fabrication technique to design microstructured piezoresistive layers, paving the way to tailor sensor performance by engineering their microstructures and to produce ultrasensitive pressure sensors at low cost.

Highly sensitive pressure sensor based on structurally modified tissue paper for human physiological activity monitoring

“…The time between P2 and P1 (Δ T DVP ) is also one of the evaluation parameters of pulse condition. Δ T DVP value is about 0.27 second, conform to the normal range of other literature reports …”

Soft Electronics for the Skin: From Health Monitors to Human–Machine Interfaces

“…Flexible piezoresistive pressure sensors have been studied extensively because of their simple sensor structure and manufacturing process, low power consumption, [105,108] wide range of pressure detection, [106] low detection limit, [131] fast response, [131] and high sensitivity. [109] However, they still suffer from disadvantages in nonlinear sensitivity [105,131,132] and high drift over time, and are also sensitive to the thermal effect. [133] Cheng et al developed a flexible piezoresistive pressure sensor which operated at a voltage of 1.5 V with low energy consumption (<30 mW), ultralow limit of detection of 13 Pa within a short time (<17 ms), high sensitivity (>1.14 kPa −1 ), and high stability, enabling real-time monitoring of the BP of a human radial artery under both a normal condition and after physical exercise, as shown in Figure 4c.…”

“…The P-wave (percussion), T-wave (tidal), and D-wave (diastolic) peaks of the human pulse waveform could all be observed, as shown in Figure 4h,i. [107] Other types of surface microstructures like pyramids, [138] microdomes, [106,139] microhumps, [105] and microsemicylinders [132] were also exploited on elastomers. The piezocapacitive pressure sensors were built with two parallel electrodes separated by elastomeric dielectrics.…”

Recent Advances in Smart Wearable Sensing Systems

“…[40] Moreover, the properties are regulated by adding small amounts of amino polymers and ethoxylated polyethylenimide. Besides, some new design ideas can further inspire researchers, such as the elastomer engineering, [41] strain engineering, [42] and the elimination of substrates. For demonstration, a conformal and self-adhesive strain sensor, which responded to human motion, was applied to a finger skin without any glue or interface material as shown in Figure 1d.…”

“…The result shows that the adhesion force between the human skin and S3-PDMS was much stronger. Besides, some new design ideas can further inspire researchers, such as the elastomer engineering, [41] strain engineering, [42] and the elimination of substrates. [43] Miyamoto et al [43] fabricated an stretchable, lightweight, ultrathin, highly gas-permeable, and inflammation-free sensors, realized with a conductive nanomesh structure due to the biocompatible and stretchable Adv.…”