Fabrication and Performance Evaluation of Highly Sensitive Flexible Strain Sensors with Aligned Silver Nanowires.

Jae Hyuk Choi,Jong Soo Ko,Dong Hwan Kim,Young Jung,Myung Gyu Shin

doi:10.3390/mi11020156

Jae Hyuk Choi, Jong Soo Ko + Show 3 more

Open Access

https://doi.org/10.3390/mi11020156

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Abstract

In this study, we fabricated strain sensors by aligning silver nanowires and transferring them with polydimethylsiloxane (PDMS) and compared the performances of the fabricated strain sensors along the alignment direction. Two types of flexible strain sensors embedded with the aligned silver nanowires were fabricated: one in the longitudinal direction, which is the same as the alignment direction, and the other in the lateral direction, which is perpendicular to the alignment direction. We then evaluated their properties. The proposed longitudinally aligned strain sensor showed the maximum sensitivity (gauge factor (GF) = 89.99) under 25% tensile conditions, which is 7.08 times higher than the sensitivity (GF = 12.71) shown by the laterally aligned strain sensor under 25% tensile conditions. This finding confirmed that the alignment direction of silver nanowires influences the sensitivity of flexible strain sensors. Furthermore, this study demonstrates that the laterally aligned strain sensor (ε > 60%) can be used in wearable devices because it satisfies the required strain range (ε > 50%). Since the strain sensors were fabricated using the temperature-controlled dip coating process, they can be produced at low cost in large quantities, and thus they have advantages for commercialization. These characteristics will be applicable to various flexible devices as well as to flexible strain sensors.

Highlights

With the development of wearable devices, there has been active research on flexible and stretchable devices
Flexible strain sensors are being researched for their wide application in wearable devices, such as sensors attached to the skin for detecting vital signs and as sensors for detecting motions of large and small magnitudes in people [2]
We evaluated the strain range and sensitivity of the fabricated sensors according to the alignment direction

Summary

Introduction

With the development of wearable devices, there has been active research on flexible and stretchable devices. Xu and Zhu produced a capacitive strain sensor using this method, and it was the first study that fabricated a conductor by transferring silver nanowires to PDMS [17]. A flexible strain sensor was fabricated by pouring PDMS onto the silver nanowires exposed to the surface. We fabricated a flexible strain sensor with a GF between 2 and 14 and a maximum strain range of 70% by adjusting the amount of silver nanowires. This result is more appropriate for application to wearable devices than other materials [18]. Polydimethylsiloxane (PDMS). (e) Transfer of the silver nanowires to the PDMS. (f) Flipped PDMS to which the silver nanowires were transferred. (g) Connecting wires to both ends of the PDMS to which silver nanowires were transferred. (h) Encapsulation of the sensor using the PDMS

Dip-Coating Process

Packaging Process

Results and Discussion

Conclusions