Series Of Progress On Flexible Wearable Electronic Skin Of Ningbo Materials

Electronic skin can mimic human skin's perception of external environment (including pressure, temperature and chemical stimulation), so it can be widely used in artificial intelligence and medical diagnosis. Although electronic skin research has made great progress in recent years, there are still many problems such as inadequate sensitivity, poor stability and anti-interference ability and narrow induction range, which limits its practical application.

To solve these problems, it is the key to select active materials with excellent properties and design reasonable device structures. Carbon nanomaterials (carbon nanotubes, graphene, etc.) are one of the most active materials for manufacturing high-performance flexible sensors because of their excellent physical, chemical and electrical properties. However, due to the inelasticity of carbon materials, when constructing flexible devices, it is often necessary to compounded with soft and elastic polymers, and at the same time maintain their own properties as far as possible. Therefore, developing effective methods to effectively compounded carbon based materials and polymers is very important for developing high-performance flexible wearable devices.

The Chen Tao research team of the Ningbo Institute of materials technology and engineering, Chinese Academy of Sciences, has developed a series of polymer composites based on carbon materials, and has made some progress. These polymer based carbon composite systems are important material bases for flexible wearable sensing devices.

Biomimetic humidity sensing materials

Imitating the life system helps to design efficient sensors. For example, water molecules are of vital importance in most metabolic processes of the human body. They can obtain the physiological and psychological information of individuals by monitoring the content and distribution of water molecules around the skin surface and exhaled air in real time. Chen Tao's team has developed a Flexible Biomimetic humidity sensitive material based on polydopamine / graphene nanoheterojunction.

This material can form regular layered two-dimensional structure film between electrodes by self-assembly, and by adjusting the amount of dopamine, the interlayer spacing can be precisely controlled in the range of 0.7~ 1.4nm. The nano scale pore structure is conducive to the rapid spanport of water molecules, which ensures the rapid response and recovery of the device. The polydopamine molecules can quickly capture and release the water molecules through hydrogen bonds, and ensure the rapid response and recovery of the devices in thermodynamics. The flexible wearable device constructed by the sensor can monitor the very weak humidity fluctuation information of human body caused by psychological activities such as breathing, movement or even lying.

Graphene sensing layer asymmetric structure sensing material

In the design of polymer based carbon composite system, especially in the application of flexible sensors, asymmetric composite helps to give full play to the performance advantages of polymer and carbon based materials. Recently, the team has worked with the researcher of Pan Cao Feng Research Institute, Beijing Institute of nano energy and systems, Chinese Academy of Sciences, and used graphene lamellae to assemble two dimensional macroscopical thin films at the water / air interface. The graphene film was used as sensing layer to form a non symmetric composite structure with a micro nano structure PDMS elastomer. The conductivity and thickness of the graphene film sensing layer can be well balanced by regulating the number of assembly layers.

The sensor exhibits excellent comprehensive performance, and has high sensitivity and wide linear detection range, good stability and super high signal-to-noise ratio. Based on these excellent performances, a set of universal, high-precision and wearable wireless pulse monitoring system is constructed. Compared with the commercial wearable pulse sensor, the sensor system has many advantages, besides having good flexibility and wearability, it also has the advantage of high accuracy, anti body movement interference, and realizes real-time detection of pulse signal in daily exercise (running or cycling). It is expected to be used for personalized diagnosis.