【Research Background 】
         Pressure sensor systems can transform strain into resistance, potential, capacitance, etc. Recently, there has been great interest in the rapid development of wearable electronic devices. There are three main types of pressure sensors: piezoresistive, piezoelectric and capacitive sensors. Among them, the piezoresistive sensor has high sensitivity, fast response and excellent stability, and can be manufactured by simple and low-cost methods such as dip coating, spin coating and laser induction, thus ensuring its wide application in bionic robot technology. . However, there are still great challenges in the selection of sensing materials.

[Introduction]
        Recently, Professor Gao Yihua of Huazhong University of Science and Technology reported that an MXene/reduced graphene oxide aerogel with 3D structure is ultra-light and super-elastic, and its pressure-sensitive property can be used in piezoresistive sensors. MX / rGO aerogel not only combines the large specific surface area of rGO and the high conductivity of MXene (Ti3C2Tx), but also has a rich porous structure, so its performance is superior to single-component rGO or MXene in pressure sensor. Large rGO nanosheets can prevent oxidation of MXene by wrapping MXene in an aerogel. More importantly, the piezoresistive sensor based on MX / rGO aerogel showed extremely high sensitivity (22.56 kPa-1), fast response time (<200 ms) and good stability over 10,000 cycles. The MX / rGO-based 3D hybrid aerogel piezoresistive sensor easily captures signals below 10 Pa to clearly test the adult‘s pulse.

          The results were published online at ACS Nano: 3D Synergistical MXene/Reduced Graphene Oxide Aerogel for a Piezoresistive Sensor.

[Graphic introduction]

Figure 1: Pressure sensor based on MX / rGO aerogel. (a) Schematic diagram of the preparation of MX / rGO aerogel. (b) Schematic diagram of the preparation of the MX / rGO aerogel based sensor. (c) Schematic diagram of the sensing mechanism.

Figure 2 Internal microstructure of MX / rGO aerogel and its in-situ dynamic process under external pressure. (a, d, g) Various magnified SEM images of MX / rGO aerogels in the initial state. (b, e, h) Various magnified SEM images of the MX / rGO aerogel under compression correspond to (a, d, g), respectively. (c, f, i) Various magnified SEM images of MX / rGO aerogels after release (b, e, h).

Figure 3 Basic sensing performance of MX / rGO aerogels. (a) I-T curves of MX / rGO aerogels with different ratios of GO / MXene (5:1, 10:1, 20:1, pure GO) under the same pressure. (b) Current change response at various applied pressures of 115 to 970 Pa. (c) I-V curve of the MX / rGO aerogel device. (d) Relative current changes with respect to applied pressure, where the four curves represent different ratios of GO / MXene (5:1, 10:1, 20:1, 1:0). (e) Response time and recovery time of MX / rGO aerogel and rGO aerogel. (f) The current output after more than 10,000 loads under a load of 510 Pa showed good durability.

Figure 4 uses the MX / rGO aerogel sensor to monitor small strains, human sounds and actions in real time; (a) Detect the current response of the small flower bud‘s pressure sensor. (b) The current response of the pressure sensor when the wearer speaks "one", "two", "three" and "four", and the inset shows a photograph of the sensor attached to the throat. (c) The current response of the jugular vein pulse (JVP) by mounting the sensor to the neck. (d) The current response of the arterial pulse wave is achieved by mounting the sensor on the wrist.

[Summary of this article]
The MXene / rGO hybrid aerogel is made by a simple ice stencil freezing technique and applied to piezoresistive sensors. Compared to pure rGO aerogels, the mechanical properties and sensitivity of MXene / rGO aerogels have been greatly improved. The sensor not only recognizes a variety of pressures, but also detects subtle health activities and even detects the pulse of the wrist. It provides a low-cost, large-scale method for manufacturing MXene-based hybrid materials and has excellent performance.

Literature link:

DOI: 10.1021/acsnano.7b06909

Source: WeChat public number   MXene Frontier