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Applications of Polymer, Composite, and Coating Materials
Ultrahigh Sensitivity Piezoresistive Pressure Sensors for Detection of Tiny Pressure Hongwei Li, Kunjie Wu, Zeyang Xu, Zhongwu Wang, Yancheng Meng, and Liqiang Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03639 • Publication Date (Web): 31 May 2018 Downloaded from http://pubs.acs.org on May 31, 2018
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ACS Applied Materials & Interfaces
Ultrahigh Sensitivity Piezoresistive Pressure Sensors for Detection of Tiny Pressure Hongwei Li, Kunjie Wu, Zeyang Xu, Zhongwu Wang, Yancheng Meng and Liqiang Li* Advanced Nano-materials Division, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou 215123, China KEYWORDS: pressure sensor, detection limit, ultralow, high sensitivity, piezoresistive
ABSTRACT: High sensitivity pressure sensors are crucial for the ultra-sensitive touch technology and E-skin, especially at the tiny pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to two hundred kPa−1, and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa−1 by using short channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels, and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 µs), excellent
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reproducibility and stability, and low power consumption. Remarkably, the sensor shows excellent detection capacity in the tiny pressure range including LED switching with a pressure of 7 Pa, ringtone (2−20 Pa) recognition, and ultrasensitive (0.1 Pa) electronic glove. This work represents a performance and strategic progress in the field of pressure sensing.
1. INTRODUCTION Flexible pressure sensors have great application perspective in the artificial electronic skin,1−16 wearable healthcare monitors,17−25 soft robotics,26−28 and flexible touch displays.4,29,30 The precise detection of the tiny pressure (< 100 Pa, especially the tiny pressure regime from several Pa down to 0.1 Pa) is important for the above applications, but relatively difficult compared to low-pressure regime (1−10 kPa, normal touch and human body circulation) and mediumpressure regime (10−100 kPa, object manipulation).4,21,31 Tiny-pressure sensors with high sensitivity will provide potential to surpass the detection capacity of human’s skin as well as to realize the applications requiring ultra-sensitive detection.21,25,31 The progresses in the sensitivity of subtle-pressure sensors have been achieved in recent years by some elaborate strategies, most of which focus on the optimization of the electrode materials and micro-structures.2,14,16,31−39 For example, Pan et al.31 fabricated a pressure sensor with an ultra sensitivity of 133.1 kPa−1 for pressures < 30 Pa based on hollow-sphere microstructure. Su et al.34 demonstrated sensitivity up to 50.17 kPa−1 for a piezo-resistive sensor based on mimosainspired micropattern in the pressure range < 70 Pa. Very recently, Wang et al.37 achieved a sensitivity of 34.47 kPa−1 at a low-pressure regime (< 400 Pa) by fabricating flexible pressure sensor with transparent carbonized silk nanofiber membranes (CSilkNM) and unstructured polydimethylsiloxane (PDMS) film. However, it can be found from Table 1 that the sensitivity (calculated with the standard method, i.e., the slope of the curve of relative current/resistance
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ACS Applied Materials & Interfaces
change versus pressure)2,3,5,32,34,35 of the state-of-the-art subtle-pressure sensors still fluctuates in the range of several to two hundred kPa−1. It seems highly challenging, if not impossible, to get bigger breakthrough to promote the sensitivity over 1000 kPa−1, which might be due to the lack of the understanding of the intrinsic and key factors governing the sensitivity. Table 1. Summary of the key parameters of subtle-pressure sensors
NO.
Materials
Sa)
DLb)
∆I/I0 or
[kPa−1]
[Pa]
Range
Tresd)
Voltage
∆R/R0 (%)c)
[Pa]
[ms]
[V]
Ref.
1
rGO-wrapped PVDF 3.1 Nanofiber
1.2
3.3
