With the rapid development of flexible electronic devices, high-density integrated stretchable strain sensing arrays are crucial for next-generation intelligent applications such as wearable electronic devices, bionic robots, and implantable medical devices. A strain sensing unit with a wide strain range, high sensitivity, fast response time, high stability, and small sensing area is a prerequisite for constructing a high spatiotemporal resolution strain sensor array. However, the strain sensors currently reported mainly rely on conductive materials based on crack mechanisms, which have inherent contradictions between sensing area and performance. Therefore, the preparation of flexible strain sensing arrays with a wide strain range, high sensitivity, and small sensing area still faces significant challenges.

Achievement display

The author proposes a novel crack control mechanism: by utilizing S-Ag coordination bonds to regulate the crack size and orientation of the sensing material S-MXene/AgNW (S-M/A) sensing thin film. The introduction of S-Ag coordination bonds regulates the local strain field of S-M/A sensing thin films, enabling the formation of high-density network cracks with an average crack size reduced to 60 µ m and an average crack gap reduced to 1 µ m. This minimizes the sensing area while ensuring the S-M/A sensing thin film has ultra-high sensitivity and a wide strain range.

The strain sensor based on MXene/silver nanowire interface interaction reported in this paper has a minimum sensing area of 0.25 mm2, and also has an ultra wide working range (0.001-37%), ultra-high sensitivity (sensitivity coefficient of about 500 at 0.001% strain and greater than 150000 at 35% strain), fast response time (about 5 ms), low hysteresis, and excellent long-term stability (can stretch release cycles more than 1000 times at 15% strain).

Innovation point

A crack control mechanism was proposed by modifying MXene with γ - mercaptopropyl triethoxysilane to obtain thiol terminated MXene (S-MXene) nanosheets. Strong, dynamic, and reversible S-Ag coordination bonds were introduced between the AgNW network and S-MXene nanosheets, resulting in dense network cracks in the S-M/A flexible strain sensor during stretching. This overcomes the inherent contradiction between sensing size and sensing performance in crack based flexible strain sensors and achieves a flexible strain sensor with a wide strain range, ultra-high sensitivity, low hysteresis, fast response, long-term stability, and a sensing area as low as 0.25 mm2.

Source: Sensor Expert Network