Yan Bin,Ding Huizhen,Zhang Yawen,Lin Pei,Wu Di,Shi Zhifeng,Chen Xu,Tian Yongtao,Li Xinjian
Skin-attachable and flexible strain sensors have attracted extensive interests because they enable to monitor individual physical actions, health status, and vibrations of sound. In this paper, multi-walled carbon nanotubes (MWCNTs) are transfer-printed into Ecoflex substrate to fabricate the MWCNT grid/Ecoflex strain sensors. We investigated the effects of the distribution and amount of MWCNTs on the sensor properties by tuning mesh sizes of nylon screens and repeated times of spray-coating and found that the distribution and amount of MWCNTs could influence on the response equilibrium process of sensors, besides the response value. Among the as-prepared samples, the sensors based on 75-mesh screens with 20-time coating exhibit the fastest equilibrium of response with a relatively high response, which the response time is about 274 ms. Meanwhile, the sensors have a good stability and durability. Furthermore, the as-prepared attachable and flexible strain sensors are capable of monitoring different finger gestures, diverse subtle motions of human body, and vibrations of sound, which demonstrate an application prospects in the fields of human motion detection, electronic skins of bionic robots, and human–machine interfaces.
Printable and stretchable conductive elastomers have promising applications for epidermal and wearable electronics, soft robotics, etc. However, these conductive materials usually present poor performances in monitoring dynamic strains. The monitored signals are distorted and lose key physical signs, which limit their practical applications. Through investigating kinetic behaviors of conductive pathways along longitudinal and transverse directions in these conductive materials, the physical mechanism of signal distortion under dynamic strains is interpreted. To overcome this strain sensing problem, an Ag-Ecoflex-polydimethylsiloxane (PDMS) elastomer by printing Ag-filler-Ecoflex-matrix ink on PDMS is proposed. Compared to other conductive materials, the Ag-Ecoflex-PDMS elastomer has preferable dynamic performances, embodying smaller overshoot response, higher strain sensitivity, and lower hysteresis. A deep-learning-based dynamic calibration method is proposed to successfully correct the sensing signals and eliminate the hysteresis error to 0.1%. Moreover, the proposed Ag-Ecoflex-PDMS elastomers gain high electrical conductivities owing to thermal expansion and contraction of PDMS substrate during the thermosetting of conductive ink, and thus can be both excellent stretchable sensors and stretchable conductors. Demonstrations of monitoring knee motion with high fidelity and human–robot collaborative playing ping-pong validate superior accuracy and robustness of the Ag-Ecoflex-PDMS elastomers for monitoring human dynamic activities, human-machine collaboration, virtual reality, etc.
Zhenwei Wang,Congcong Luan,Guangxin Liao,Jiapeng Liu,Xinhua Yao,Jianzhong Fu
High-performance stretchable strain sensors, particularly those with high sensitivity and broad sensing range, are highly important for wearable devices. Herein, a novel auxetic bilayer conductive mesh strain sensor (ABSS), composed of multi-hardness silicones, is proposed and fabricated by the direct ink writing 3D printing and ink spraying technique. The bilayer conductive mesh comprises a thin layer of high-conductive and crack-prone single-walled carbon nanotubes (SWCNTs) coated on a stretchable carbon-black-doped Ecoflex silicone rubber (CB/Ecoflex) mesh. The former serves as the dominant sensing material by generating SWCNT cracks in the full strain range, while the latter mainly plays the roles of both generating the resistance change and maintaining the conductive paths under high strain conditions. The presence of high-hardness auxetic frame contributes to the formation of longitudinal SWCNT cracks on transverse meshes, enhancing the sensitivity of the sensors. It is shown that the synergistic effect of the bilayer conductive mesh, strain concentration, and auxetic deformation strategy endow ABSS with a high gauge factor (∼ 13.4) that is 6.6 times larger than that of the common sensor. Additionally, this study demonstrates the superior sensing performance of the ABSS for wearable applications including swallowing recognition, respiration monitoring, and joint movement detection.
危险品化学品经营许可证（带存储）