Hybrid Architectures of Heterogeneous Carbon Nanotube Composite Microstructures Enable Multiaxial Strain Perception with High Sensitivity and Ultrabroad Sensing Range

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.201803411.Low-dimensional nanomaterials are widely adopted as active sensing elements for electronic skins. When the nanomaterials are integrated with microscale architectures, the performance of the electronic skin is significantly altered. Here, it is shown that a high-performance flexible and stretchable electronic skin can be produced by incorporating a piezoresistive carbon nanotube composite into a hierarchical topography of micropillar-wrinkle hybrid architectures that mimic wrinkles and folds in human skin. Owing to the unique hierarchical topography of the hybrid architectures, the hybrid electronic skin exhibits versatile and superior sensing performance, which includes multiaxial force detection (normal, bending, and tensile stresses), remarkable sensitivity (20.9 kPa −1 , 17.7 mm −1 , and gauge factor of 707 each for normal, bending, and tensile stresses), ultrabroad sensing range (normal stress = 0-270 kPa, bending radius of curvature = 1-6.5 mm, and tensile strain = 0-50%), sensing tunability, fast response time (24 ms), and high durability (>10 000 cycles). Measurements of spatial distributions of diverse mechanical stimuli are also demonstrated with the multipixel electronic skin. The stress-strain behavior of the hybrid structure is investigated by finite element analysis to elucidate the underlying principle of the superior sensing performance of the electronic skin. Electronic Skins www.advancedsciencenews.com

Hierarchically Microstructure-Bioinspired Flexible Piezoresistive Bioelectronics

“…After 50 000 cycles, almost no obvious degradation in current amplitude (Figure g) indicates excellent repeatability, stability, and durability, which is crucial to practical applications of the sensor. Compared with the previously reported flexible sensors based on microstructures and fibers, − ,– the as-prepared pressure sensor shows both high sensitivities, relatively wide detection range, and excellent robustness (Figure h), which is mainly attributed to the hierarchical microstructure of bioinspired microdome-structured electrodes and HPPNFs. In addition, a linear pressure-sensing capability over an exceptionally broad pressure range (5.2–98.7 kPa) was achieved at the expense of sensitivity (0.05 kPa –1 ) in the sensor with single-sided microstructure electrodes (Figure S6, Supporting Information).…”

“…(g) Durability test of flexible sensor by applying more than 50 000 cycles without signs of fatigue. (h) Comparison of the detection pressure range and sensitivity between this work and the reported pressure sensors in refs − and − .…”

A Pressure-Insensitive Self-Attachable Flexible Strain Sensor with Bioinspired Adhesive and Active CNT Layers

“…Interestingly, when nanomaterials are incorporated into specific microstructures such as micropillars [25,26], microdomes [27], micropyramids [28,29], and microwrinkles [30], the sensing performance of flexible tactile sensors is significantly altered when compared with that of nanomaterial-based simple thin-film sensors. This is because microstructures with specific topographies induce stress concentrations and exhibit unique force-displacement behaviors under the influence of specific mechanical stimuli [27,31].…”

Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

“…Liu et al reported a nanopile interlocking device that can be used for stretchable electrodes and strain sensors [12]. Sun et al also devised a multifunctional electronic skin based on reversible interlocking of micropillar-wrinkle hybrid structures [13]. Ko et al utilized Ge/parylene hybrid nanowires to develop a reusable, self-selective connector that exhibits strong shear adhesion in both dry and wet conditions [3].…”