Recent Advances in Printed Capacitive Sensors

Abstract

In this review paper, we summarize the latest advances in the field of capacitive sensors fabricated by printing techniques. We first explain the main technologies used in printed electronics, pointing out their features and uses, and discuss their advantages and drawbacks. Then, we review the main types of capacitive sensors manufactured with different materials and techniques from physical to chemical detection, detailing the main substrates and additives utilized, as well as the measured ranges. The paper concludes with a short notice on status and perspectives in the field.

Keywords: inkjet printing; interdigitated electrodes; roll-to-roll; screen printing; spray deposition.

Figure 1

Variables in capacitive sensors: (a) Distance (x) between plates; (b) Capacitor area (electrode moving in x direction); (c) Dielectric properties.

Figure 2

Dynamic response of the force sensor with 100 μm polydimethylsiloxane (PDMS) thick from [86]. Insets: Upside—Picture of the fabricated sensor. Downside—Hybrid integrated system with inkjet-printed silver layers and PDMS force sensor.

Figure 3

(a) Design of printed shear force sensor from [99]; (b) Image of the inkjet silver electrodes; (c) Capacitance response (red) to a normal force (blue) over time. (b) The solid red line corresponds to the capacitance change due to a force in – direction and the dashed line to the + direction.

Figure 4

Layout of the designed and characterized electrodes in [85]: (a) interdigitated electrodes (IDE) sensor; (b) Meandered capacitor; (c) Spiral electrodes and (d) Serpentine electrode (SRE) capacitor. (e) Normalized sensitivity to RH as a function of frequency for each electrode configuration.