Development of a proximity sensor with vertically monolithic integrated inductive and capacitive sensing units

Abstract

This study designs and implements a proximity sensor consisting of inductive and capacitive sensing units. These two sensing units are vertically monolithic integrated on a single chip using the micro-fabrication processes. In addition, low-temperature fabricated nanoporous anodic aluminum oxide (np-AAO) is employed as the dielectric layer to enhance the performance of capacitive sensing. The characteristics of the presented vertically monolithic integrated inductive and capacitive proximity sensor are as follows: (1) enlarged sensing distance of conductive objectives: capacitive sensing unit for short distance detection and inductive sensing unit for long distance detection, (2) non-conductive object can be detected by the capacitive sensing unit, (3) fringe effect capacitive sensing is enhanced by the spiral coil electrode and (4) np-AAO has good dielectric properties (the dielectric constant is 11.9 in this study) for capacitive sensing. In application, various materials (including metal, plastic and a human finger) have been successfully detected by the presented sensor. Preliminary results demonstrate that the typical fabricated proximity sensor has a sensing range of 0.5–5 mm for the metal rod. In comparison, the inductive and capacitive sensing units have the sensing ranges of 1.5–5 and 0.5–3 mm, respectively. Moreover, the non-conductive plastic rod can be detected by the capacitive sensing unit.

Transparent and Flexible Cellulose Nanocrystal/Reduced Graphene Oxide Film for Proximity Sensing

“…These C/O values were obtained by elemental analysis of the samples. When the finger approaches the material the fringe electric field is disturbed due to a tiny electric charge transfer from the finger, which causes a fluctuation in the output signal . The sensitivity of the m‐r(CNC/GO) sensor arrays is about 5 times higher in amplitude compared to that of m‐rGO (Figure c) because of its high surface‐to‐volume ratio and charge‐storage capacity at junctions related to the hydrophilic functional groups, such as carboxyl groups, that affect the environmental humidity.…”

“…Though these sensor materials generally are based on many mechanisms such as electromagnetic induction, infrared emission, ultrasonic wave detection etc., capacitance or resistance measurements still offer an easier way. Using this principle, several polymers and their nanocomposites have been assimilated in touch screens, media players, and satellite‐navigation systems as short‐range proximity sensors . However, eco‐friendly, transparent, non‐metallic, and low‐cost sensor materials of reduced size that would be useful in various electronic fields are still under investigation.…”

“…[5][6][7] However, eco-friendly, transparent, non-metallic, and low-cost sensor materials of reduced size that would be useful in various electronic fi elds are still under investigation.…”

Nanocellulose-Graphene Hybrids: Advanced Functional Materials as Multifunctional Sensing Platform

“…Currently, driven innovation in intelligent human-machine interactions and digital human healthcare [160] is attracted attention by green fabricating integrated short-range proximity sensors to detect bio-signals without physical contact with different proximity sensing mechanisms [160][161][162][163].…”

Displacement Measurement Realized By Near-field Coupling Between Multiple Coils

“…(4)(5)(6)(7)(8) A variety of sensing techniques have been developed for contactless displacement sensing in the past decades, for example, the eddy current, capacitive, optical, and inductive displacement sensors. (4,9,10) Optical sensors have better accuracy, stability, and linearity than all other sensors, but they are usually bulky and costly owing to the requirements of a laser, lens, and electronic components. The capacitive sensor can achieve exceptionally high resolution and stability, and yet it is quite sensitive to dust and pollutants in the air-gap or electrode surface.…”