Metal Mesh as a Transparent Omnidirectional Strain Sensor

Abstract

developed in recent years. The stretchable conductors used in those sensors work via piezoresistive sensing mechanism, such as thin metal films (TMFs) deposited onto stretchable polymers [18][19][20] and some filler-type elastomers composed of carbon nanotubes, [16,17] graphene, [21,22] and metal nanowires. [14,[23][24][25][26][27][28] Particularly, TMFs strain sensors are feasible to be prepared in a large area by direct deposition approach, making it compatible with conventional Si-based processes and easy to integrate into external circuits and devices. However, the stiff feature of TMFs will lead to mechanical failure when stretched over their elongation limit, e.g., less than 1% for thin Cu films. [19] To resolve this problem, various structures with wavy, buckle, wrinkle, or network topography have been introduced to adapt mechanical deformation. [29][30][31][32][33] However, these strain sensors are operated only in uniaxial or biaxial stretching directions, [29] not suitable for the omnidirectional model, which is crucial for practical applications. For example, a strain sensor attached to the human body will inevitably suffer from multidimensional strain. Developing multidimensional TMFs-based strain sensor is highly demanded while still a challenge. It is noteworthy that metal mesh films are possibly stretched in all direction, taking a honeycomb metal mesh film as an example. A simulated polyethylene terephthalate (PET) mesh with a honeycomb structure that consists of regular hexagonal cells is depicted in Figure 1a. The ratio of pore size diameter D to the frame width W (D/W) is controlled to be 5/1 (Figure 1d). The experiments by stretching PET meshes show that the elongation degree along X-direction is higher than that on Y-direction (Figure 1b,c). The maximum elongation along X-direction (e max-x ) and Y-direction (e max-y ) (calculated from Equations E1 and E2 in the Supporting Information) are 41.2% (Figure 1e) and 15.2% (Figure 1f), respectively.The above simulation results demonstrate that a singledomain honeycomb metal mesh features an anisotropic elongation depending on the grid orientation, such as the metal grid transparent conductors fabricated by laser sintering of silver nanoparticle ink and laser ablation of copper film. [34,35] For structures fabricated by self-assembly process, such as the metal meshes prepared by breath-figure approach, are composed of multiple domains with various grid orientation due to the existence of line defects. [36,37] This merit results in isotropic characteristics, such as uniform conductivity and stretchability in a large area. In this work, we prepare a transparent, highly stretchable, and omnidirectional strain sensor using porous honeycomb-structured Ag mesh film that consists of multiple Thin metal films can be engineered to fabricate strain sensors by conquering their stiffness using wavy, buckle, or wrinkle topography. However, these structures usually operate in uniaxial or biaxial stretching directions, limiting their application in the omnidirecti...

Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors

“…For example, a sandwich structure PDMS/AgNWs/PDMS- (AgNWs thin film embedded between two layers of PDMS) based strain sensor was reported with high stretchability up to 70% and controllable linearity sensing performance [ 91 ]. Also, Ag mesh/PDMS strain sensor with honeycomb lattices and multiple domains as sensitive unit was introduced for the sensitive and transparent sensor applications [ 94 ].…”

Directional Freezing Assisted 3D Printing to Solve a Flexible Battery Dilemma: Ultrahigh Energy/Power Density and Uncompromised Mechanical Compliance

“…From various dimensions such as loading density, areal capacity, and capacity retention rate, our printed thick electrodes surpass those of other LFP/LTO-based thick electrodes (Table S1, Supporting Information). [24,28,[40][41][42][43][44] Since thick vertical channel LFP/CNT/CNF cathode and LTO/CNT/CNF anode exhibit approximate capacities of 153.8 and 168.5 mAh g −1 at 0.2 C, LFP/LTO full cells are assembled with two identical layered cathode and anode, and their electrochemical performance are studied under different loading densities and deformation conditions. The electrochemical performance of full cells assembled with different layered cathode and anode are tested and the corresponding results are listed in Table 1.…”

Self-Sensing Cellulose Structures With Design-Controlled Stiffness

“…As such, using a kirigami structure instead of a honeycomb with θ < 15.0 • is far more reasonable. This results in the model shown in (6).…”

“…Figure 8. Plot of the ratios determined using FEM on honeycomb structures with various angles of θ , the actual measured ratios and their 95% confidence intervals, which are denoted as uncertainties, the initial honeycomb model shown in (2) and the unified model shown in (6).…”