The pace to pursuit electronic skin (e-skin) has never stopped from scientific fiction to new kinds of multifunctional e-skins, since they have broad applications in intelligent robots, biomimetic prosthetics，health monitoring, and many other areas. However, current strain sensing materials are of deficiencies for practical applications, such as poor electrical conductivity, large energy consumption, complex manufacturing process and high cost. Therefore, exploration of new strain sensitive materials for e-skin is of crucial significance.
Metals and alloys are one of the oldest and most widely used materials but suffer from small elastic limit (<0.5%), which makes them uncompetitive when being used to e-skin. Metallic glasses which are alloys of disordered atomic packing shows ten times larger elastic limit than conventional alloys. Based on metallic glasses, Haijie Xian from the Institute of Physics, Chineses Academy of Sciences, under the guidance of Prof. Wei-hua Wang, Prof. Haiyang Bai, Prof. Yanhui Liu has developed a new flexible strain sensor which was named “Metallic glass skin”.
Metallic glass skin, synthesized by depositing metallic glass thin film Zr55Cu30Ni5Al10 on flexible substrate polycarbonate, exhibits piezoresistance effect with a gauge factor around 2.86, large detectable strain range (~1% or 180 degree bending angle, ideal elastic limit is 4.2% in room temperarure)，good conductivity (>5000S cm-1)，and extremely low temperature coefficient of resistance (9.04×10-6 K-1). In addition, the metallic glass skin shows distinct antibacterial behavior, excellent reproducibility and repeatability (over 1000 times), nearly perfect linearity, low manufacturing cost, and negligible energy consumption. The combination of these features is essential for e-skin’s practical applications. Besides demonstrating a candidate material for e-skin, this work also provides unprecedent perspective on functional use of metallic glasses by combining its superb electrical, mechanical and thermal properties together.
This study, published in Applied Physics Letters (111, 121906, 2017), was supported by the National Science Foundation, MOST 973 Program of China and the Key Research Program of Frontier Sciences, the Chinese Academy of Sciences.