A Highly Sensitive Capacitive‐Based Soft Pressure Sensor Based on a Conductive Fabric and a Microporous Dielectric Layer

Abstract

parallel plate capacitive sensing technology is popular due to signal repeatability, temperature insensitivity, and relative simplicity of design and construction. [34,35] In this approach, when an external force is applied to the soft pressure sensor, the dielectric layer thickness of the sensor varies, which leads to a change in the capacitance of the sensor. However, due to relatively small changes in the capacitance of parallel plate sensors under loading, achievable sensitivities are typically very low. [21] Therefore, most studies focus on the modification of the dielectric layer to increase sensitivity. In this context, efforts toward increased sensitivity can be grouped into two main categories: surface modification of the elastomer layers and the creation of micropores within the dielectric layer. In the first approach, topographical features [36][37][38][39][40] (such as nanoscale pyramids, microstructured line patterns, or micrometer-scale circular pillars) are created on the elastomer surface via surface micromachining methods (such as photolithography and molding). However, It should be noted here that, even though high sensitivity can be achieved using surface micromachining, the working range is typically limited to <10 kPa that is undesirable for most wearable applications. The latter approach focuses on the creation of a porous dielectric layer [41][42][43][44] and a recent trend is to use solid particle leaching [44][45][46][47][48] to create micropores within the silicone elastomer. As commercially available sugar cubes and silicone elastomers can be used, manufacturing is quick, simple, and low cost. It has been shown that increased sensitivity over the tactile pressure range was achieved using this method due to the reduced stiffness of the dielectric material as well as increased effective dielectric constant due to the presence of air gaps within the microporous structure. Capacitance values are typically on the order of several femtofarads due to the dielectric layer thickness (height of the sugar cube templates is around 10 mm), but a higher baseline capacitance is needed for sufficient signal-to-noise in the presence of parasitic capacitances within the readout circuitry in these systems. Beside, carbon-based materials, [46] conductive thin films [48] are generally employed to construct electrode layers and are used in combination with the modified dielectric layer for the formation of the soft sensor. However, to integrate these sensors into the system for the creation of wearable electronic devices, the sensors themselves must be flexible, robust, and have mechanically In this paper, the design and manufacturing of a highly sensitive capacitivebased soft pressure sensor for wearable electronics applications are presented. Toward this aim, two types of soft conductive fabrics (knitted and woven), as well as two types of sacrificial particles (sugar granules and salt crystals) to create micropores within the dielectric layer of the capacitive sensor are evaluated, and the combined effec...

Point-of-use robotic sensors for simultaneous pressure detection and chemical analysis

“…S2, ESI ‡). This is 3-5 fold higher than those of other unpatterned porous elastomeric structures in a similar pressure regime, 22,24,25 and with a higher operating range compared to a different PDMS foam structure that exhibited similar relative capacitance change. 21 While the DC/C 0 per 10 kPa pressure value of our pressure sensor is 3-4 fold lower than that of photolithographically patterned porous PDMS sensors, its fabrication process is much simpler.…”

“…20 Indeed, the sensitivity of porous structures was found to be around 1-2 orders of magnitude higher compared to that of non-porous dielectrics using the same material. [22][23][24][25] Porous structures with well-defined patterns usually exhibit higher sensitivity than arbitrary patterns; 12,21,23 however, their fabrication is highly complex. Here, the foam structures of the pressure sensors are easy to fabricate and are optimized by air-to-solid volume ratios for sensitivity and reproducibility to the range of pressures typical for object manipulation in the low (1-10 kPa) and medium (10-30 kPa) pressure regimes.…”

Ultrasensitive, Low‐Voltage Operational, and Asymmetric Ionic Sensing Hydrogel for Multipurpose Applications

“…Generally, soft elastomer and conductive materials are indispensable components to build a highly sensitive tactile sensor . It is also found that structural design is critical to determine the sensitivity of tactile sensors . With micro/nanostructured elastomers or conductors, the tactile sensors can possess very high sensitivities and other functions.…”

Monolithic Dual‐Material 3D Printing of Ionic Skins with Long‐Term Performance Stability

“…In these cases, the compressibility of the elastic dielectric film ensures large variations in the capacitance under pressure loading, which significantly affects the sensitivity of the sensors. It has been shown that introducing super‐low elastic modulus dielectric materials (e.g., ecoflex silicone and Dragon skin) or designing air‐trapped microstructured dielectric layers (e.g., pyramidal elastomer, foamed dielectric, and fabric dielectric), sensitivity will get improved dramatically, since the deformation resistance of the structured sensing devices is far less than that of the nonstructured ones. However, the preparation process to realize the designed microstructures usually requires a complex and time‐consuming mold transferring procedure, in which the mold is fabricated based on chemical etching or photolithographic technique, thus limiting the fabrication scale and the structure diversity …”