Istanbul Technical University

About: Istanbul Technical University is a education organization based out in Istanbul, Turkey. It is known for research contribution in the topics: Fuzzy logic & Large Hadron Collider. The organization has 12889 authors who have published 25081 publications receiving 518242 citations. The organization is also known as: İstanbul Teknik Üniversitesi & Technical University of Istanbul.

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

Abstract: DOI: 10.1002/admt.201700237 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[36–40] (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[41–44] and a recent trend is to use solid particle leaching[44–48] 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 effects on the sensor’s overall performance are assessed. It is found that a combination of the conductive knit electrode and higher dielectric porosity (generated using the larger sugar granules) yields higher sensitivity (121 × 10−4 kPa−1) due to greater compressibility and the formation of air gaps between silicone elastomer and conductive knit electrode among the other design considerations in this study. As a practical demonstration, the capacitive sensor is embedded into a textile glove for grasp motion monitoring during activities of daily living.