Flexible Sensor based on Three Dimensional Polymer Nanocomposites

Significance 

Flexible strain sensor, an electronic device that is sensitive to the applied strain, has the advantage of ordinary one for excellent monitoring of mechanical force, at the same time processes a good flexibility and deformation capacity, thus have become an ideal material for wearable electronics due to their simple structure and facile fabrication process. Traditional strain sensor due to the rigid conducting basement is incompressible and tough resulting in a mechanical mismatch that limits the functionality of these devices for wearable electronics. To overcome these challenges, an ideal strategy to achieve fully flexible sensor is to enable the conducting basement themselves to be deformable, which possess the ability to maintain good electrical function under deformation. Polymer nanocomposites filled with carbon nanotubes (CNTs) have attracted much attention to satisfy the material requirements for flexible sensors. Much progress has been made in this field with varying degree of success, however, if the material was effectively used as reinforcement, proper dispersion of CNTs into the polymer matrix had to be guaranteed. In addition, there was a concern that dispersed CNTs had a tendency to re-agglomerate in the polymer matrix during the processing of nanocomposites, especially for those using thermosetting and rubbery matrices which generally required a curing process under a raising temperature. In this context, CNTs with three-dimensional (3-D) structures, such as foam, aerogel, sponge, were developed in recent years to overcome these problems, furthermore, 3-D structure endow CNTs more space to deform under strain.

In this view, researchers from Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, developed a new fabrication for flexible polymer-based nanocomposites reinforced by CNT foam conducting basement and explore their electrical properties and piezoresistive property. In their approach, CNT foam with 3-D structure was fabricated via CVD process by using cotton as a template to solve the problems arising from the dispersion and possible reagglomeration of nanofillers in a polymer matrix. The results showed that by using cotton as a template, CNTs were grown on the carbonized cotton fiber, forming hierarchical structures with excellent electrical conductivity, structure stability, hydrophobic and absorption performance, thus providing a convenient way to prepare nanocomposites by monomer self-diffusion. For polymer matrix, polydimethylsiloxane (PDMS), a kind of silicone-based elastomers, was chosen as the elastomer matrix on the basis of high elasticity and flexibility over a broad range of strains. In nanocomposites, the introduction of CNTs onto the carbonized cotton fiber significantly enhances the piezoresistive performance of nanocomposites with high reliability and sensitivity. The CNT foam nanocomposite possessed a wide sensing range in the compression strain of 0%-80%, a high sensitivity of 104 at 60% strain.

In summary, a facile method to prepare CNT foam with excellent electrical conductivity, structure stability, hydrophobic and absorption performance was developed, and this method solved the tough issue of CNT dispersion. The novel 3-D structure of CNT foam was able to deform under compression, endowing nanocomposites a wide response range and high sensitivity for external mechanical load.

Flexible Sensor based on Three Dimensional Polymer Nanocomposites - Advances in Engineering

About the author

Qing Ma is currently a PhD candidate at the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. She received her BSc degree in polymer material and engineering from Beijing Technology and Business University (2014). She has published 5 technical papers in highly reputable journals, such Composites Science and Technology, Carbon, Composites Communications and Journal of Non-Crystalline Solids. She has delivered a presentation in The 10th Asian-Australasian Conference on Composite Materials 2016. Her main research interests include wearable electronics, structural health monitoring, nanotechnology and nanocomposites.

About the author

Dr. Bin Hao is an assistant professor in the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. He received his BSc and PhD degrees from Dalian Ocean University (2010) and University of Chinese Academy of Sciences (2017). He has authored or co-authored 9 research papers, 3 patents and two book chapters in the field of composites science and technology. His current research interest lies in the design and preparation of polymer nanocomposites for environmental remediation.

About the author

Prof. Peng-Cheng Ma obtained his BSc and MSc from Lanzhou University, and PhD from The Hong Kong University of Science and Technology. From 2010 to 2012, he was working in Leibniz Institute of Polymer Research Dresden in Germany. Professor Ma joined the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Science in 2012.

Professor Ma has been active in polymer composites/nanocomposites. Currently, his works focus on materials with hierarchical structures for engineering and environmental applications. He authored a monograph, 2 book chapters and published more than 65 papers in the broad field of material science and engineering with a total citation of 6400. Professor Ma’s other research achievements include two Best Paper Awards from the 5th Asian-Australasian Conference on Composite Materials and the 9th International Symposium on Electronic Materials and Packaging, an Overseas Research Award to support him to carry out joint research in Korea Advanced Institute of Science and Technology, Humboldt Research Fellowship, Outstanding Youth for Nature Science in Xinjiang Uygur Autonomous Region, and so on. Because of the diligent effort and expertise in the field of composites science and technology, Professor Ma was awarded Composites Part A–Editor’s Top Reviewer Award 2015, Career Award of Western Light Program in 2016. He was elected as a Fellow of Royal Society of Chemistry (FRSC, UK) in 2018. More recently, he was awarded Excellent Young Scientist by the Chinese Society of Composite Materials.

Besides fundamental research, Professor Ma is enthusiastic in transferring knowledge to technology for various applications. He is a co-founder of CAS-Realnm, a hi-tech company working on separation science and technology. He pioneered the research on polymer nanocomposites for oil-water separation, and this project was awarded the 3rd Class in the China Innovation and Entrepreneurship Competition 2017.

Reference

Qing Ma, Bin Hao, Peng-Cheng Ma. Flexible sensor based on polymer nanocomposites reinforced by carbon nanotube foam derivated from cotton. Composites Science and Technology, volume 192, 108103, 2020.

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