A flexible and transparent ceramic nanobelt network for soft electronics

In the near future, scientists and researchers hope to use semiconducting materials in various human-friendly electronic devices such as skin-like sensors and interactive electronics, which require them to function properly while being bent, stretched or twisted. In this work, we managed to achieve excellent mechanical flexibility in conventionally fragile ceramics with a design of nanobelt network. We engineered inorganic oxides into ultralong and continuous nanobelts via an extremely simple and scalable electrospinning process. The as-synthesized SnO2 nanobelts possess ultrahigh aspect ratios (>105) and well-defined rectangular cross-section, which exhibit outstanding mechanical flexibility under a bending radius down to 1 mm and show no obvious electrical degradation after 1000 cycles of bending to a radius of 2 mm. Moreover, the free-standing nanobelt network demonstrates superior optoelectronic properties as well as high optical transparency (>80% transmittance at 550 nm), which enables us to construct conformable and ‘invisible’ UV photodetectors on multiple flexible or curved substrates, including plastics, paper, textiles and curved/bio-surfaces. These results strongly indicate the great compatibility and potential of inorganic nanobelt networks as flexible and transparent functional electronics. Inorganic semiconductors - such as tin dioxide - are extensively used in electronic applications. However, as they are typically brittle such materials are not well-suited to the development of flexible devices. An approach to circumventing this issue is to prepare one-dimensional materials, which are better able to withstand mechanical stresses. Hui Wu and Wei Pan from Tsinghua University in China and co-workers have now engineered a tin dioxide material with promising properties that consists of a network of uniform ‘nanobelts’. The material is prepared by electrospinning synthesis, a straightforward route that is easily scalable. The resulting long and thin nanobelts can be reversibly bent over 1,000 times and form a freestanding film with good optoelectronic properties, as well as a high optical transparency - a desirable attribute for practical devices. Flexible and transparent electronics, such as interactive digital products and human-friendly health-care monitors, are expected to fundamentally change the way of our daily life. Inorganic semiconductors, as a class of important functional materials, are key components of electronic devices. However, their applications in soft electronics are severely confined due to the brittleness. We demonstrate that by structural design of a nanobelt network, extraordinary mechanical flexibility and high optical transparency can be achieved in conventionally fragile ceramics. High-performance photodetectors based on this inorganic nanobelt network are demonstrated on multiple flexible substrates, which strongly indicates its great potential in soft electronics.