Research group of Academician Wang Zhonglin, Beijing Institute of nano energy and system, Chinese Academy of Sciences: self powered plantar pressure imaging system

Since the concept of nano generator and self energy supply system came out, researchers have developed various friction nano generators and composite nano generators to collect mechanical energy that is widely existed in the environment and is wasted, and collect these small energy as power supply for small-scale electrical equipment to realize self energy supply system At the same time, the self energy sensor or health monitoring system based on nano generator has also been widely and deeply studied As the physiological data such as heart rate, blood pressure and blood glucose content, the information of plantar pressure distribution is also of great significance for health monitoring However, the existing plantar pressure monitoring system is either bulky, inconvenient to wear and real-time measurement, or limited by the service life of traditional batteries, unable to monitor for a long time Recently, in order to overcome the limitations of traditional batteries, under the leadership of Academician Wang Zhonglin, director of the Institute of nano energy and systems of the Chinese Academy of Sciences and director Professor of the lifelong School of Georgia Institute of technology, a research team composed of Tang Wei, associate researcher, Deng Chaoran (co authored) and others developed a self powered foot pressure imaging system It can meet the needs of continuous and long-term real-time monitoring (DOI: 10.1002/adfm.201801606) Academician Wang Zhonglin is a scientist with important academic influence in the field of international nanotechnology His research is original, forward-looking and leading Academician Wang Zhonglin first invented piezoelectric nano generator in 2006 and successfully developed friction nano generator in 2012 Nano generator can directly convert mechanical energy into electrical energy output, providing a new mode for effective collection of mechanical energy In addition, nano generator can also be used as self driving sensor to detect mechanical model The research group focuses on the research of piezoelectric and friction nano generator and piezoelectric electronics application basis, functional devices and integrated systems, including nano energy devices, active micro nano sensors, self driving nano devices and systems, and explores their applications in new energy, sensor networks and human-computer interaction, typical examples include wearable friction nano generator energy Collection device (ACS appl Mater Interfaces, 2014, 6, 14695-14701; nano res., 2015, 8, 3934-3943; nano res., 2018, DOI: 10.1007/s12274-018-1978-z); friction Nanogenerator driven wireless sensor (nano technology, 2014, 25, 225402), friction electronics field effect transistor and logic circuit (adv mater., 2015, 27, 3353-3540); Nano res., 2017, 10, 3534-3542), tactile sensor and electronic skin (ACS Nano, 2016, 20, 10912-10929; ACS Nano, 2016, 10, 8078-8086; adv funct Mater., 2016, 26, 4906-4913), collecting large-scale blue energy - ocean energy (acsnano, 2015, 9, 12562-12572; nano energy, 2017, 39, 9-23; nature, 2017, 542 , 159; ACS Nano , 2018 , 12 , 1849-1858 ）。 Wang Zhonglin graduated from northwest Telecommunication Engineering College (now known as Xi'an University of Electronic Science and Technology) in 1982, and was admitted to CUSPEA in the same year In 1987, he received a Ph.D in physics from Arizona State University and worked as a professor of John Cowley, an international authority in electronic microscopy Dr Wang Zhonglin is now a chair professor of the University of Georgia Institute of technology, a lifetime Chair Professor of Hightower, an outstanding Chair Professor and director of the center for characterization of nanostructures, director and chief scientist of Beijing Institute of nano energy and systems, Chinese Academy of Sciences, foreign academician of Chinese Academy of Sciences and academician of European Academy of Sciences Wang Zhonglin is an internationally recognized leader in the field of nanotechnology He has made great contributions to the preparation and characterization of one-dimensional oxide nanostructures and their applications in energy technology, electronic technology, optoelectronic technology and biotechnology The piezoelectric Nanogenerator and friction Nanogenerator were invented, and the concept of self driving system was put forward at first The research of nanostructured piezoelectric electronics and piezoelectric optoelectronics was pioneered, which opened up a new way for the development of micro nano electronic system Wang Zhonglin has published more than 1300 Journal Papers (31 of which are published in science, nature and nature subjournals), 6 scientific monographs and more than 200 patents in the world-class journals He has been invited to give more than 850 lectures and special reports His academic papers have been cited more than 113000 times, and the h-index is 165 He is one of the top five authors in the world who cited the most materials and nanotechnology papers, and the 25th most outstanding scientist in the world Cutting edge research achievements: self powered plantar pressure imaging system, Beijing Institute of nano energy and systems, Chinese Academy of Sciences, has made a series of pioneering work in the field of self driving systems and self driving sensors In 2011, Academician Wang Zhonglin first proposed the concept of self driving system (nano letters, 2011, 11, 2572-2577) He pointed out that a complete integrated self driving system consists of energy collector, energy memory, sensor, data processor, control unit and communication system Figure 1: schematic diagram of self driving system structure (source: nano letters, 2011, 11, 2572-2577) The key of self driving system is to have an energy collector to collect the energy existing in the environment, including but not limited to the mechanical energy of vibration, sound, wind and water conservancy, as well as thermal energy, solar energy and chemical energy In order to make good use of the energy in the surrounding environment, the composite energy unit which is combined with nano generator and can collect mechanical energy and other energy at the same time is invented Friction nano generator can also be combined with traditional electromagnetic generator, and the friction electromagnetic composite nano generator can effectively collect mechanical energy (nanotechnology, 2014, 25, 135402; nano res., 2018, DOI: 10.1007/s12274-018-1978-z) Figure 2: friction electromagnetic composite Nanogenerator (source: nano res., 2018, DOI: 10.1007/s12274-018-1978-z) in addition to being an energy collection device, another application of Nanogenerator is active sensor In this regard, Academician Wang Zhonglin's research team has completed a series of pressure sensors based on piezoelectric nanogenerators and pressure / tactile sensors based on friction nanogenerators (nano lett., 2012, 12, 3109-3114; extreme mechanics letters, 2015, 2, 28-36; science advances, 2017, 3, e1700694; advanced Mater., 2017, 29, 1606346; ACS Nano , 2018, 12, 254 – 262), these sensors not only have potential application value in the field of intelligent electronic equipment and human-computer interaction, but also provide a new solution for long-term biological signal detection As the physiological signals such as heart rate and pulse, plantar pressure distribution is also an important physiological signal, especially the pressure values of heel, lateral middle foot and metatarsal bone, which are important medical indicators for diagnosing diseases and preventing plantar injury Traditional plantar pressure monitoring system, either because of the large size of the test board, inconvenient to wear, or limited by power consumption and battery life, can not achieve long-term continuous monitoring In order to solve this problem, the research team used PVDF based piezoelectric nano generator as self energy sensor to directly install 32 PVDF piezoelectric films on FPC Compared with the multi-step micro structure processing technology, this method can produce a large number of pressure sensor arrays which can be integrated into intelligent insoles at a low cost Figure 3: schematic diagram of self powered plantar pressure imaging system: (a) schematic diagram of plantar pressure imaging system (b) Structure diagram of the sensor including PVDF film and FPC (c) How a single sensor works under pressure (d) SEM images of PVDF films (e) An optical image of the entire plantar pressure imaging system (source: advfunct mater., 2018, 28 (23), 201801606) due to PVDF piezoelectric nano generator Because of the problems of high output impedance and more pyroelectric noise, the original output signal can not be directly used Therefore, the author designs a charge amplifier to convert the original output into a voltage signal which can be directly used by commercial electronic chips At the same time, the output characteristics, response speed and durability of the sensor and the sensor unit composed of the charge amplifier are tested And the possible impact of the working environment on it In order to meet the practical needs, the effects of the output of each channel in the whole array on the change of pressure are tested when the metal weight is rolling and people are walking As shown in Fig 4 (B, c), during the whole process of the weight rolling through each sensor in turn, the pressure causes the output of different channels It can be clearly seen that each channel has a rapid response to the weight rolling, and there is no mutual influence between the channels Figure 4 (d) shows the response of each channel to human motion Figure 4: schematic diagram of the location of the pressure sensing unit selected in test (a) of the sensor array (b) When a heavy object rolls over a flexible circuit board pasted with a pressure sensor array, the output of the sensor unit changes (c) When the flexible circuit board with pressure sensor array is worn to walk, the output of the selected sensor unit changes (d) The change of pressure is shown in the form of strength diagram (source: advfunct mater., 2018, 28 (23), 201801606) the experimental results show that the heel first contacts the sensor, at this time, the channel corresponding to the position of No 3 and No 8 sensors will have a rapid increase in output response; as the action continues, the output of No 3 and No 8 decreases, and the foot pressure distribution moves forward, and No 5 and No 6 can be seen The corresponding channel of sensor No.1 will have the rising voltage output; when the walking action is about to be completed and the forefoot force leaves the ground, it can be seen that the corresponding channel output of sensor No.5 and sensor No.6 decreases rapidly, while the output of the corresponding charge amplifier of sensor No.1 and sensor No.2 rises first and then decreases slowly with the change of the traveling state This is the result of the pressure sensor based on PVDF piezoelectric nano generator and the charge amplifier as the analog signal conditioning circuit In order to convert the pressure signals collected from the pressure into digital signals, the team has developed a DAQ to convert the data collected from each channel The converted results are transmitted to the mobile terminal through Bluetooth 4.2 protocol By using the Android application, the whole plantar pressure imaging system can accurately monitor and visually display the real-time pressure distribution during walking More importantly, DAQ has a very low working current, which means that the nano generator designed in the previous work can provide power for the data acquisition circuit: by combining with the friction electromagnetic composite nano generator, the team developed a self powered, continuous real-time pressure distribution monitoring system Figure 5: for plantar pressure imaging system