SCIENCE CHINA Materials, Volume 61 , Issue 12 : 1587-1595(2018) https://doi.org/10.1007/s40843-018-9267-3

Flexible and transparent capacitive pressure sensor with patterned microstructured composite rubber dielectric for wearable touch keyboard application

More info
  • ReceivedFeb 14, 2018
  • AcceptedMar 28, 2018
  • PublishedApr 27, 2018


The development of pressure sensors with highly sensitivity, fast response and facile fabrication technique is desirable for wearable electronics. Here, we successfully fabricated a flexible transparent capacitive pressure sensor based on patterned microstructured silver nanowires (AgNWs)/polydimethylsiloxane (PDMS) composite dielectrics. Compared with the pure PDMS dielectric layer with planar structures, the patterned microstructured sensor exhibits a higher sensitivity (0.831 kPa−1, <0.5 kPa), a lower detection limit, good stability and durability. The enhanced sensing mechanism about the conductive filler content and the patterned microstructures has also been discussed. A 5×5 sensor array was then fabricated to be used as flexible and transparent wearable touch keyboards systems. The fabricated pressure sensor has great potential in the future electronic skin area.

Funded by

the National Science Foundation for Distinguished Young Scholars of China(NSFC,61625404)

the Key Research Program of Frontier Sciences


the NSFC(61504136)


This work was supported by the National Natural Science Foundation for Distinguished Young Scholars of China (NSFC, 61625404), the Key Research Program of Frontier Sciences, CAS (QYZDY-SSW-JWC004) and the NSFC (61504136).

Interest statement

The authors declare no conflict of interest.

Contributions statement

Shi R and Lou Z designed the devices and experiments; Shi R performed the experiments; Shi R, Lou Z and Chen S analyzed the data; Shi R and Chen S synthesized the Ag nanowires; Shi R wrote the paper with support from Lou Z and Chen S. All authors contributed to the general discussion.

Author information

Ruilong Shi received his BSc degree from Jilin University in 2015. Now he is a graduate student at the Institute of Semiconductors, Chinese Academy of Sciences. His research interest focuses on flexible pressure sensor and wearable electronic devices.

Zheng Lou received his PhD degree from Jilin University in 2014. He joined the Institute of Semiconductors, Chinese Academy of Sciences as an Assistant Professor in 2014 and was promoted to Associate Professor in 2018. His current research focuses on flflexible electronics, including pressure sensors, electronic-skin, transistors and photo-detectors.

Guozhen Shen received his BSc degree in 1999 from Anhui Normal University and PhD degree in 2003 from the University of Science and Technology of China. From 2004 to 2013, he conducted his research in Hanyang University (Korea), National Institute for Materials Science (Japan), University of Southern California (USA) and Huazhong University of Science and technology. He joined the Institute of Semiconductors, Chinese Academy of Sciences as a professor in 2013. His current research focuses on flexible electronics and printable electronics, including transistors, photodetectors, sensors and flexible energy-storage devices.


Supplementary information

Supporting data are available in the online version of the paper.


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  • Figure 1

    Schematic illustration for the fabrication of (a) micropatterned Si mould and (b) flexible microstructured AgNWs/PDMS composite dielectric film.

  • Figure 2

    (a) Architecture of the flexible capacitive pressure sensor. (b) The photo image of a single pressure sensor device. (c) Top and (d) tilted SEM images of the micro-structured AgNWs/PDMS film. (e) Optical transmittance of the AgNWs/PDMS films with various mixing ratios of AgNWs.

  • Figure 3

    (a) Schematic illustration of the sensing mechanism of the capacitive pressure sensor. (b) Capacitance changes of the non-patterned sensors under pressure with various mixing ratios of AgNWs. (c, d) Sensitivity curves of the pressure sensor with different types of dielectric layer under applied pressure. The micro-structured sensor based on AgNWs/PDMS dielectric layer with 0.12 wt% AgNWs exhibits higher pressure sensitivity than that based on the non-patterned or micro-structured PDMS dielectric layer without AgNWs. (e) Comparison of the sensing performance of our work and previous research results [8,17,19,20,22,25,27,28].

  • Figure 4

    Characterization of capacitive pressure response of the sensor with the microstructured 0.12 wt% AgNWs/PDMS dielectric layer. (a) Reliable capacitance change of the sensor under different pressures. (b) Repeated real-time response curves of both types of micro-structured sensors under pressures of 0.1 kPa and 0.2 kPa, respectively. (c) Fast response time (<30 ms) and relaxation time of the sensor. (d) Transient response to the placing and removal of a small piece of paper, the first corresponding to a pressure of only 1.4 Pa. (e) Capacitance change curves recorded after 1,000, 2,000, 5,000, 7,000 and 10,000 cycles, respectively under a pressure of 1 kPa. (f) Magnified view of (e) after 7,000 loading-unloading cycles.

  • Figure 5

    (a) Schematic illustration of the final flexible e-skin device and an enlarged pixel with a sandwich structure. (b) System-level block diagram of the wireless printed circuit board (PCB) showing the signal switching, conditioning, processing and wireless transmission paths from sensors to the mobile application (numbers in parentheses indicate the corresponding labelled components in the photo of the wireless PCB). The flexible sensor array is able to achieve the function of the keyboard (c). Demonstrations such as real-time inputting word “f” (d) and “flextronics” (e) are shown in the mobile application.

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