A Flexible Proximity Sensor Fully Fabricated by Inkjet Printing

Chin-Tsan Wang,Wei-Chia Liao,David T W Lin,Yuh-Chung Hu,Hua-Wei Lin,Kuo-Yi Huang

doi:10.3390/s100505054

Chin-Tsan Wang, Wei-Chia Liao + Show 4 more

Open Access

https://doi.org/10.3390/s100505054

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Abstract

A flexible proximity sensor fully fabricated by inkjet printing is proposed in this paper. The flexible proximity sensor is composed of a ZnO layer sandwiched in between a flexible aluminum sheet and a web-shaped top electrode layer. The flexible aluminum sheet serves as the bottom electrode. The material of the top electrode layer is nano silver. Both the ZnO and top electrode layers are deposited by inkjet printing. The fully inkjet printing process possesses the advantages of direct patterning and low-cost. It does not require photolithography and etching processes since the pattern is directly printed on the flexible aluminum sheet. The prototype demonstrates that the presented flexible sensor is sensitive to the human body. It may be applied to proximity sensing or thermal eradiation sensing.

Highlights

Flexible sensors have emerging applications in biomedicine, artificial skin, and wearable electronics [1]
One of the ways to make the sensor flexible is to fabricate the sensor device or circuit directly on flexible substrates. This is exactly the way adopted in this work because it is the most direct and innovative approach to the manufacturing of large-area flexible electronic devices
Flexible electronics are embedded into the fibers or clothes to make clothing with the ability to monitor biological aspects

Summary

Introduction

Flexible sensors have emerging applications in biomedicine, artificial skin, and wearable electronics [1]. Thin film pyroelectric sensors possess the advantages of being integrable with integrated circuits (IC), un-cooled detecting, operation at room temperature, fast and wide spectral responses, high sensitivity, and low cost [2,3]. Among the aforementioned methods the sol-gel method is low cost and it allows the production of large-area films with good homogeneity and the chemical ingredients and concentration are easy to control For these reasons the sol-gel method had been applied in ZnO thin film deposition processes. In general photon type detectors have the advantages of faster response and high sensitivity, and the disadvantages of complicated structures, low operation temperature (lower than room temperature), and high cost. The thermal type detectors have the advantages of low cost, simple structures, and operation at room temperature while their main disadvantage is a slower response. The prototype successfully demonstrates sensitivity to the human body and may be applied in situations requiring thermal detection

The Sensor Structure

Preparation of Inkjet Solutions

Fabrication Process

Signal Measurement

Prototype Demonstration

Conclusions