Fabrication and Characterization of Roll-to-Roll Printed Air-Gap Touch Sensors

Although printed electronics technology has been recently employed in the production of various devices, its use for the fabrication of electronic devices with air-gap structures remains challenging. This paper presents a productive roll-to-roll printed electronics method for the fabrication of capacitive touch sensors with air-gap structures. Each layer of the sensor was fabricated by printing or coating. The bottom electrode, and the dielectric and sacrificial layers were roll-to-roll slot-die coated on a flexible substrate. The top electrode was formed by roll-to-roll gravure printing, while the structural layer was formed by spin-coating. In particular, the sacrificial layer was coated with polyvinyl alcohol (PVA) and removed in water to form an air-gap. The successful formation of the air-gap was verified by field emission scanning electron microscopy (FE-SEM). Electrical characteristics of the air-gap touch sensor samples were analyzed in terms of sensitivity, hysteresis, and repeatability. Experimental results showed that the proposed method can be suitable for the fabrication of air-gap sensors by using the roll-to-roll printed electronics technology.

Two-Parameter Elliptical Fitting Method for Short-Cavity Fiber Fabry–Perot Sensor Interrogation

To solve the cavity interrogation problem of short cavity fiber Fabry–Perot sensors in white light spectral interrogation with amplified spontaneous emissions (ASEs) as the white light sources, a data processing method, using an improved elliptical fitting equation with only two undetermined coefficients, is proposed. Based on the method, the cavity length of a fiber Fabry–Perot sensor without a complete reflection spectrum period in the frequency domain can be interrogated with relatively high resolution. Extrinsic fiber Fabry–Perot air-gap sensors with cavity lengths less than 30 μm are used to experimentally verify the method, and are successfully interrogated with an accuracy better than 0.55%.

Study of Mechanism for Wear Adjustment with Electro Wedge Brake

Electro wedge brake (EWB) have been suggested and improved for enhancing the braking efficiency and reducing the weight and power of actuating motor than electro mechanical brake (EMB). This is due to self-reinforcement features of the wedge mechanism. On the other hand, the conventional hydraulic brake system has the passive wear adjustment without any sensors and actuators. This is because of the sealing rubber which is disposed between the hydraulic cylinder and piston, and supply the piston’s same restoring strokes regardless of pad’s wear amounts. This feature leads to the uniform distance between the disc and the pad. In comparison, electronic brake systems such as EMB and EWB don’t have the hydraulic piston and cylinder with the sealing rubber. Therefore the electronic brake systems cannot use the function of this passive wear adjustment. However, if the electronic brake system has gap sensors for detecting distances between the pad and the disc, and actuators for keeping the uniform distances between the pad and the disc, then the brake system can have the function of wear adjustments. One of our research goals is the embodiment of cost-effective and feasible wear adjustment mechanism which is proper to EWB. In this paper, as a chain of EWB’s development, we describe the proposed mechanism for wear adjustment with EWB. Further we describe the feasibility of this mechanism with the simulation study.