Stretchable Motion Memory Devices Based on Mechanical Hybrid Materials

Liu, Yaqing; Liu, Zhiyuan; Zhu, Bowen; Yu, Jiancan; He, Ke; Leow, Wan Ru; Wang, Ming; Chandran, Bevita K.; Qi, Dianpeng; Wang, Hong; Chen, Geng; Xu, Cai; Chen, Xiao

doi:10.1002/adma.201701780

Cited by 77 publications

(76 citation statements)

References 58 publications

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“…The characteristic relaxation time roughly ranges from 50 to 400 µs (Figure S8, Supporting Information), in agreement with previous results . The fast relaxation characteristics of the flexible TS device are sufficient for most flexible functional sensory elements, which typically show a relaxation time from 1 ms to 10 s . The flexible TS device can withstand an endurance of over 10 6 cycles under the 100 µs/2 V programming pulses and 100 µs/0.3 V read pulses, with a 1.8 ms wait time between each program and read pulse (Figure S9, Supporting Information).…”

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confidence: 82%

Enhancing the Matrix Addressing of Flexible Sensory Arrays by a Highly Nonlinear Threshold Switch

Wang

Leow

et al. 2018

Advanced Materials

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The increasing need for smart systems in healthcare, wearable, and soft robotics is creating demand for low-power sensory circuits that can detect pressure, temperature, strain, and other local variables. Among the most critical requirements, the matrix circuitry to address the individual sensor device must be sensitive, immune to disturbances, and flexible within a high-density sensory array. Here, a strategy is reported to enhance the matrix addressing of a fully integrated flexible sensory array with an improvement of 10 fold in the maximum readout value of impedance by a bidirectional threshold switch. The threshold switch shows high flexibility (bendable to a radius of about 1 mm) and a high nonlinearity of ≈10 by using a nanocontact structure strategy, which is revealed and validated by molecular dynamics simulations and experiments at variable mechanical stress. Such a flexible electronic switch enables a new generation of large-scale flexible and stretchable electronic and optoelectronic systems.

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confidence: 82%

Enhancing the Matrix Addressing of Flexible Sensory Arrays by a Highly Nonlinear Threshold Switch

Wang

Leow

et al. 2018

Advanced Materials

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“…The modulus of PDMS can be regulated by the mass ratio of base monomer to curing agent, which is not suitable to making a single piece of PDMS film with domains of different modulus. Till now, the main strategy to realize different mechanical domains in a single film is embedding rigid materials, e.g., polyimide, polyethylene terephthalate, and photoresist, into the elastomers . However, the photolithography fabrication process is complicated, and the interface between different materials is hard to control in the current method.…”

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confidence: 99%

Mechanocombinatorially Screening Sensitivity of Stretchable Strain Sensors

et al. 2019

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are often realized at the expense of stretchability, and vice versa. Hence, developing strain sensors with customizable sensitivity could be vital for reliable sensing. The sensitivity of resistive-type strain sensors is defined by gauge factor, GF = (ΔR/R 0 )/ε, where ΔR is the resistance change with strain, R 0 is the resistance before strain, and ε is the applied strain. [28] Currently, a large number of stretchable strain sensors are developed based on conductive materials, such as carbon nanotubes, graphene, metal networks, and liquid metal. [1,2,26,[29][30][31][32][33][34] The sensitivity is highly scattered and independent due to different sensing materials and diverse fabrication methods (Table S1, Supporting Information). Thus, it still remains a challenge to screen out the specific sensitivity from these traditional strain sensors.The resistive-type stretchable strain sensors are typically composed of conductive films and polymer substrates. [28,35,36] The mechanism involves the transfer of strain from the substrate to the conductive film during stretching, which induces cracks and thus increases electrical resistance; when the strain is released, the resistance returns to its initial value. [6] Hence, the strain distribution of polymer substrates largely determines the resistance-strain behavior of the conductive film, thereby determining sensitivity. According to mechanics of materials, strain is uniformly distributed over a mechanically homogeneous film ( Figure S1, Supporting Information). In contrast, taking a simplest mechanically heterogeneous film for example, strain is redistributed over the film, and local strain is determined by two factors, mechanics and structure parameters ( Figure S2, Supporting Information). Therefore, for the resistive-type stretchable strain sensors, the sensitivity could be screened via strain distribution of substrates. Based on finite element modeling (FEM), strain is indeed redistributed on mechanically heterogeneous substrates, which are composed of low and high modulus regions (Figure 1a,b). Numerous gradient structures can be precisely obtained by changing the parameter of substrates. By combining both mechanics and structure parameters of the substrates, a strategy we termed mechanocombinatorics, strain redistribution could be systematically studied. The strain enhancement is well customized by mechanically combined parameters, modulus ratio and pitch, which can be directly extracted from the strain enhancement library (Figure 1c). Stretchable strain sensors have aroused great interest for their application inhuman activity recognition, health monitoring, and soft robotics. For various scenarios involving the application of different strain ranges, specific sensitivities need to be developed, due to a trade-off between sensor sensitivity and stretchability. Traditional stretchable strain sensors are developed based on conductive sensing materials and still lack the function of customizable sensitivity. A novel strategy of mechanocombinatorics is proposed to scr...

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“…During the past decade, flexible electronic devices have earned great achievements and attracted much interests, [1][2][3][4][5][6][7] especially the stretching sensor which has been greatly developed in wearable electronics devices, [8][9][10][11][12][13][14] flexible luminescence devices [15][16][17][18] and soft robotics. [19][20][21][22][23][24][25] Among different kinds of stretching sensor, ionic conductive hydrogel stretching sensor is considered to be the best materials for the human body motion sensor, due to the good electrochemical performance [26][27][28][29][30][31][32][33][34] and controllable mechanical properties.…”

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confidence: 99%