Flexible
multidirectional strain sensors capable of simultaneously
detecting strain amplitudes and directions have attracted tremendous
interest. Herein, we propose a flexible multidirectional strain sensor
based on a newly designed single-layer hierarchical aligned micro-/nanowire
(HAMN) network. The HAMN network is efficiently fabricated using a
one-step femtosecond laser patterning technology based on a modulated
line-shaped beam. The anisotropic performance is attributed to the
significantly different morphological changes caused by an inhomogeneous
strain redistribution among the HAMN network. The fabricated strain
sensor exhibits high sensitivity (gauge factor of 65 under 2.5% strain
and 462 under larger strains), low response/recovery time (140 and
322 ms), and good stability (over 1000 cycles). Moreover, this single-layer
strain sensor with high selectivity (gauge factor differences of ∼73
between orthogonal strains) is capable of distinguishing multidimensional
strains and exhibits decoupled responses under low strains (<1%).
Therefore, the strain sensors enable the precise monitoring of subtle
movements, including radial pulses and wrist bending, and the rectification
of pen-holding posture. Benefitting from these remarkable performances,
the HAMN-based strain sensors show potential applications, including
healthcare and complex human motion monitoring.
Hierarchical metal grids are proven to be a promising solution for achieving high‐performance flexible transparent electrodes (FTEs) due to their significantly enhanced conductivity without noticeably sacrificing transparency. This work develops a one‐step mask‐free line‐shaped laser lithography by separated pulse laser ablation to efficiently fabricate large‐area FTEs composed of hierarchical metal grids, namely microscale grids interconnected with aligned nanowire arrays. The linewidth of aligned wires is highly controllable from the nanometer scale far beyond the diffraction limit (<λ/10) to the micrometer scale. This work experimentally studies the overall performance of FTEs to provide a guideline for selecting the layout and feature sizes of hierarchical metal grids. Hierarchical metal grids with 50 nm nanowires aligned inside the microscale grids show outstanding optoelectronic properties and mechanical stability, with sheet resistance of 4.6 Ω sq−1, transmittance of 82.9%, and a tiny increase in sheet resistance less than 4% after 1000 cycles of bending tests. These results prove that the line‐shaped laser lithography technique is a facile, low‐cost, and high‐throughput fabrication method for high‐performance FTEs.
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