Effect of Metal Thickness on the Sensitivity of Crack-Based Sensors

Abstract

Among many attempts to make a decent human motion detector in various engineering fields, a mechanical crack-based sensor that deliberately generates and uses nano-scale cracks on a metal deposited thin film is gaining attention for its high sensitivity. While the metal layer of the sensor must be responsible for its high performance, its effects have not received much academic interest. In this paper, we studied the relationship between the thickness of the metal layer and the characteristics of the sensor by depositing a few nanometers of chromium (Cr) and gold (Au) on the PET film. We found that the sensitivity of the crack sensor improves/increases under the following conditions: (1) when Au is thin and Cr is thick; and (2) when the ratio of Au is lower than that of Cr, which also increases the transmittance of the sensor, along with its sensitivity. As we only need a small amount of Au to achieve high sensitivity of the sensor, we have suggested more efficient and economical fabrication methods. With this crack-based sensor, we were able to successfully detect finger motions and to distinguish various signs of American Sign Language (ASL).

Crack-based and Hair-like Sensors Inspired from Arthropods: A Review

“…When the two layers are tightly bonded together, the crack on one side can propagate to the other. The method of adding multi-layer materials is a new way to solve the problem of low adhesion [79] ; (b) schematic diagram of CBS for multiple interlayers [80] ; (c) schematic diagram of the fabricating steps and composition of PMSCSS [84] ; (d) upper left: When compressive strain F is applied, adjacent fracture surfaces reconnect and overlap, allowing electric current to pass through the connection area. Bottom left: Schematic representation of the relaxed and stimulated state.…”

“…Lee et al reported CBS by depositing a few nanometers of chromium (Cr) and gold (Au) on a PET film ( Fig. 7b) [80] . In addition, the relationship between the thickness of the metal layer and the characteristics of the sensor was also investigated.…”

Highly durable crack sensor integrated with silicone rubber cantilever for measuring cardiac contractility

“…Typical highsensitivity sensors in the field of microelectromechanical system (MEMS) include silicon nanowires (SiNWs), graphene or carbon nanotube (CNT) composites, crack sensors, etc. [10][11][12][13][14][15][16][17][18][19][20][21]. Koumela et al…”

Foot Plantar Pressure Measurement System Using Highly Sensitive Crack-Based Sensor

“…We used a 7.5 µm thick PI film (3022-5 Kapton thin film, Chemplex, Palm City, FL, USA) as a substrate of the crack-based sensor. According to a previous study, the depth and density of cracks are important factors that determine the sensor's sensitivity, and the thickness of the chromium is closely related to the depth of cracks [37,38]. Sensors have high sensitivity when the chromium layer is 60 nm thick and the gold layer is 20 nm thick, due to deep cracks and the low crack density effect (performance degradation due to a small number of cracks).…”