Recent Progress in Flexible Pressure Sensor Arrays

Abstract

Flexible pressure sensors that can maintain their pressure sensing ability with arbitrary deformation play an essential role in a wide range of applications, such as aerospace, prosthetics, robotics, healthcare, human-machine interfaces, and electronic skin. Flexible pressure sensors with diverse conversion principles and structural designs have been extensively studied. At present, with the development of 5G and the Internet of Things, there is a huge demand for flexible pressure sensor arrays with high resolution and sensitivity. Herein, we present a brief description of the present flexible pressure sensor arrays with different transduction mechanisms from design to fabrication. Next, we discuss the latest progress of flexible pressure sensor arrays for applications in human-machine interfaces, healthcare, and aerospace. These arrays can monitor the spatial pressure and map the trajectory with high resolution and rapid response beyond human perception. Finally, the outlook of the future and the existing problems of pressure sensor arrays are presented.

Keywords: flexible sensing; pressure sensors; sensor arrays.

Figure 1

(a) A PDMS/MWCNT-based tactile sensor array with coplanar electrodes for crosstalk suppression. Reproduced with permission from Ref. [60]. Copyright 2016, Luxian Wang et al. (b) A tactile-direction-sensitive and stretchable electronic skin based on human-skin-inspired interlocked microstructures. Reproduced with permission from Ref. [61]. Copyright 2014, American Chemical Society. (c) A sensor array based on a highly sensitive, broad-range, hierarchically structured reduced graphene oxide/PolyHIPE foam. Reproduced with permission from Ref. [63]. Copyright 2019, American Chemical Society. (d) A flexible and self-powered dual-parameter temperature–pressure sensor array using microstructure-frame-supported organic thermoelectric materials. Reproduced with permission from Ref. [64]. Copyright 2015, Fengjiao Zhang et al. (e) A quantum-effect-based flexible and transparent pressure sensor array with ultrahigh sensitivity and sensing density. Reproduced with permission from Ref. [65]. Copyright 2020, Lan Shi et al. (f) A behavior-learned cross-reactive sensor matrix for intelligent skin perception. Reproduced with permission from Ref. [66]. Copyright 2020, WILEY-VCH.

Figure 3

(a) A bionic single-electrode electronic skin unit based on a piezoelectric nanogenerator. Reproduced with permission from Ref. [77]. Copyright 2018, American Chemical Society. (b) A screen printing of a flexible piezoelectric-based device on polyethylene terephthalate and paper for touch- and force-sensing applications. Reproduced with permission from Ref. [79]. Copyright 2017, Elsevier. (c) A scalable imprinting of a flexible multiplexed sensor array with distributed piezoelectricity-enhanced micropillars for dynamic tactile sensing. Reproduced with permission from Ref. [80]. Copyright 2020, WILEY-VCH. (d) A flexible sensor array used for touch applications and mapping of force distribution. Reproduced with permission from Ref. [80]. Copyright 2020, WILEY-VCH. (e) A skin-inspired piezoelectric tactile sensor array with crosstalk-free row + column electrodes for spatiotemporally distinguishing diverse stimuli. Reproduced with permission from Ref. [81]. Copyright 2021, Weikang Lin et al.

Figure 5

(a) A triboelectric sensor array for self-powered static and dynamic pressure detection and tactile imaging. Reproduced with permission from Ref. [88]. Copyright 2013, American Chemical Society. (b) An integrated flexible, waterproof, transparent, and self-powered tactile sensing panel. Reproduced with permission from Ref. [93]. Copyright 2016, American Chemical Society. (c) A large-area integrated triboelectric sensor array for wireless static and dynamic pressure detection and mapping. Reproduced with permission from Ref. [94]. Copyright 2019, John Wiley and Sons.

Figure 6

(a) A self-powered, high-resolution, and pressure-sensitive triboelectric sensor array for real-time tactile mapping. Reproduced with permission from Ref. [91]. Copyright 2016, WILEY-VCH. (b) A metal-electrode-free, fully integrated, soft triboelectric sensor array for self-powered tactile sensing. Reproduced with permission from Ref. [92]. Copyright 2020, Lingyun Wang et al. (c) Electrode structural design of the cross type. Reproduced with permission from Ref. [91]. Copyright 2016, WILEY-VCH. (d) A highly stretchable, transparent, and self-powered triboelectric tactile sensor with metallized nanofibers. Reproduced with permission from Ref. [95]. Copyright 2017, WILEY-VCH. (e) A self-powered sensor array for high-resolution pressure sensing. Reproduced with permission from Ref. [97]. (f) Triboelectrification-enabled touch sensing for self-powered position mapping and dynamic tracking with a flexible and area-scalable sensor array. Reproduced with permission from Ref. [98]. Copyright 2017, Elsevier.

Figure 9

(a) Real-time pressure mapping in a smart insole system based on a sensor array. Reproduced with permission from Ref. [115]. Copyright 2020, Juan Tao et al. (b) Artificial intelligence toilet (AI-Toilet) for an integrated health monitoring system using smart triboelectric pressure sensor arrays. Reproduced with permission from Ref. [116]. Copyright 2021, Elsevier. (c) Intrinsically stretchable electronics with ultrahigh deformability to monitor dynamically moving organs. Reproduced with permission from Ref. [119]. Copyright 2022, Shaolei Wang et al.

Figure 2

(a) A tunable, ultrasensitive, and flexible pressure sensor array based on wrinkled microstructures. Reproduced with permission from Ref. [71]. Copyright 2019, American Chemical Society. (b) A flexible, stretchable, and wearable multifunctional sensor array for static and dynamic strain mapping. Reproduced with permission from Ref. [72]. Copyright 2015, WILEY-VCH. (c) A skin-inspired highly stretchable and conformable matrix network for multifunctional sensing. Reproduced with permission from Ref. [73]. Copyright 2018, Qilin Hua et al. (d) A conductive fiber-based ultrasensitive textile pressure sensor. Reproduced with permission from Ref. [74]. Copyright 2015, WILEY-VCH. (e) A flexible, transparent, sensitive, and crosstalk-free capacitive tactile sensor array based on graphene electrodes and air as a dielectric. Reproduced with permission from Ref. [75]. Copyright 2017, WILEY-VCH. (f) A graded intrafillable-architecture-based iontronic pressure sensor array with ultra-broad-range high sensitivity. Reproduced with permission from Ref. [76]. Copyright 2020, Ningning Bai et al.

Figure 4

(a) High-resolution electroluminescent imaging of pressure distribution using a piezoelectric nanowire LED array. Reproduced with permission from Ref. [82]. Copyright 2013, Nature Publishing Group. (b) A flexible and controllable piezo-phototronic pressure-mapping sensor matrix with a ZnO NW/p-Polymer LED array. Reproduced with permission from Ref. [83]. Copyright 2015, WILEY-VCH. (c) Achieving high-resolution pressure mapping via a flexible GaN/ZnO nanowire LED array with the piezo-phototronic effect. Reproduced with permission from Ref. [84]. Copyright 2019, Elsevier. (d) A CdS nanorod/organic hybrid LED array and the piezo-phototronic effect of the device for pressure mapping. Reproduced with permission from Ref. [85]. Copyright 2016, Royal Society of Chemistry. (e) A dynamic pressure mapping of personalized handwriting by a flexible sensor array based on the mechanoluminescence process. Reproduced with permission from Ref. [86]. Copyright 2015, WILEY-VCH.

Figure 7

(a) A full-dynamic-range pressure sensor matrix based on dual-mode optical and electrical sensing. Reproduced with permission from Ref. [99]. Copyright 2017, WILEY-VCH. (b) Diagram of pressure regimes and the relevant applications in our daily lives. Reproduced with permission from Ref. [99]. Copyright 2017, WILEY-VCH.

Figure 8

(a) Electrooculography and tactile perception in a collaborative interface for 3D human–machine interaction. Reproduced with permission from Ref. [110]. Copyright 2022, American Chemical Society. (b) A scalable tactile glove consisting of a sensor array with 548 elements covering the entire hand. Reproduced with permission from Ref. [67]. Copyright 2019, Subramanian Sundaram et al. (c) Spatial pressure distribution capability test of a 5 × 5 sensor array using plastic boards that are shaped like the letters “U”, “J”, and “N”. Reproduced with permission from Ref. [111]. Copyright 2019, WILEY-VCH. (d) An image of a numeric keypad with braille. Reproduced with permission from Ref. [111]. Copyright 2019, WILEY-VCH.

Figure 10

Conformable, programmable, and step-linear sensor array for large-range wind pressure measurements on a curved surface. Reproduced with permission from Ref. [122]. Copyright 2020, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature.