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. 2024 Apr 8;15(1):3048.
doi: 10.1038/s41467-024-47408-z.

Ultrafast piezocapacitive soft pressure sensors with over 10 kHz bandwidth via bonded microstructured interfaces

Yuan Zhang #  1 , Xiaomeng Zhou #  2 , Nian Zhang #  3 , Jiaqi Zhu  1 , Ningning Bai  1 , Xingyu Hou  1 , Tao Sun  4 , Gang Li  1 , Lingyu Zhao  1 , Yingchun Chen  5 , Liu Wang  6   7 , Chuan Fei Guo  8
Affiliations

Ultrafast piezocapacitive soft pressure sensors with over 10 kHz bandwidth via bonded microstructured interfaces

Yuan Zhang et al. Nat Commun. .

Abstract

Flexible pressure sensors can convert mechanical stimuli to electrical signals to interact with the surroundings, mimicking the functionality of the human skins. Piezocapacitive pressure sensors, a class of most widely used devices for artificial skins, however, often suffer from slow response-relaxation speed (tens of milliseconds) and thus fail to detect dynamic stimuli or high-frequency vibrations. Here, we show that the contact-separation behavior of the electrode-dielectric interface is an energy dissipation process that substantially determines the response-relaxation time of the sensors. We thus reduce the response and relaxation time to ~0.04 ms using a bonded microstructured interface that effectively diminishes interfacial friction and energy dissipation. The high response-relaxation speed allows the sensor to detect vibrations over 10 kHz, which enables not only dynamic force detection, but also acoustic applications. This sensor also shows negligible hysteresis to precisely track dynamic stimuli. Our work opens a path that can substantially promote the response-relaxation speed of piezocapacitive pressure sensors into submillisecond range and extend their applications in acoustic range.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Design of microstructured pressure sensors with a bonded interface via topological interlinks.
a Schematic and SEM image of the conventional microstructured pressure sensor with a non-bonded interface. b Schematic and SEM image of our pressure sensor with a bonded interface. c Finite element simulations of both non-bonded and bonded pressure sensors under the loading process. d Comparison of normalized increased contact area ΔA/D in a loading-unloading cycle. e Comparison of normalized energy loss in a loading-unloading cycle. f Normalized change in capacitance as a function of pressure of the bonded pressure sensor. g The response-relaxation times of the sensor with a bonded interface and the sensor with a non-boned interface. h Comparison of our sensor and existing capacitive sensors in terms of response time and relaxation time. i Comparison of our sensor with existing capacitive sensors in terms of detectable pressure limit and corresponding frequency range.
Fig. 2
Fig. 2. Effect of microcone structure on response-relaxation time.
a Geometric parameters of the microcone. b Simulated energy loss versus pressure of microcones with various heights H. c Contour plot of critical buckling pressure of 20 microcones. d Simulated energy loss versus pressure of microcones with various bonded areas A. e Normalized capacitance change versus pressure of microcones with various bonded areas. The dotted data are experimental results. f Contour plot of normalized energy loss of 20 microcones. g SEM of microcone arrays with different bonding ratios. h Response-relaxation time of microcones arrays with different bonding ratios. Error bars represent the standard deviation of three repeated measurements of the time.
Fig. 3
Fig. 3. Effect of material on response-relaxation time.
a Storage modulus (E’), loss modulus (E”) and their ratios of pure PDMS (with elastomer and curing agent ratio of 5:1), PDMS-CNTs composite (with 2 wt.% CNTs and 7 wt.% CNTs). b Adhesion force of pure PDMS (with elastomer and curing agent ratio of 15:1 and 5:1), PDMS-CNTs composite (with 2 wt.% CNTs and 7 wt.% CNTs). c The adhesion strength of 2 wt.% PDMS-CNTs with three different interfaces. d Response time of six sensors: sensors with non-boned interfaces consisting of three different dielectric layers made of pure PDMS (with elastomer to curing agent ratios of 15:1 and 5:1) and PDMS-CNTs composite and sensors with a bonded interface based on three different dielectric layers of pure PDMS (with elastomer to curing agent ratios of 15:1 and 5:1) and PDMS-CNTs composite. Error bars represent the standard deviation of three repeated measurements of the time. e Relaxation time of the six sensors mentioned in (d). f Dynamic response of the sensor as a function of time under a pressure of 100 kPa. g Normalized change in capacitance of the sensor during the loading and unloading cycle at a pressure of 100 kPa. h Response of the pressure sensor to cyclic rubbing (10,000 cycles) under a combination of pressure (200 kPa) and a shear (45 kPa). The friction test was performed by applying a sheet of #1000 sandpaper to the surface of the sensor.
Fig. 4
Fig. 4. Sensing performance of our sensor to high-frequency mechanical vibrations.
a Schematic of the wide-frequency mechanical stimuli detection and recording platform. b Capacitive response of the pressure sensor to the mechanical vibration at a fixed frequency of 12,500 Hz, showing the fast response time of our sensor. c The corresponding frequency spectra of the signals in (b). d Signal amplitude of the capacitive response to the vibration frequency from 200 Hz to 12,000 Hz between sensors with bonded (upper panel) and non-bonded (lower panel) interfaces. e Corresponding STFT spectrograms of (d). f Static pressure (~100 kPa) detection and vibrations detection with frequencies of 500, 4000, 8000, and 12,500 Hz under a static base pressure of ~100 kPa. g Vibrational signals with frequencies of 1000.0, 1000.2, 1000.4, and 1000.6 Hz were detected using the pressure sensor. h Frequency spectra of the signals in (g).
Fig. 5
Fig. 5. Application of our sensor for sound detection.
a Schematics of the biological system and the artificial system for sound detection. b Capacitance change as a function of sound pressure. c Capacitance change as a function of sound pressure level. d Normalized change in capacitance of the system at different sound wave frequencies. SPL = 98 dB. e Acoustic waveforms recorded by a cellphone, by the sensor with a bonded interface and a non-bonded interface. f Corresponding STFT spectrograms of the acquired sound waveforms in (e).
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