In the natural world, organisms can respond accurately and rapidly to the stimulation of the external environment. This is the result of hundreds of thousands of years of natural selection and an important feature of life. With the development of materials science and the increasing demand for material properties, it is expected that man-made materials can make a certain degree of perception or feedback on external stimuli, that is, it has an environmental response that is comparable to that of organisms. Therefore, the environmentally-responsive material may be defined as a material that undergoes a reversible change in the nature of the external physical or chemical stimuli, such as changes in temperature, pH, light field, electric field, magnetic field, and stress. However, traditional environment-responsive materials are mainly polymer materials, such as hydrogels, which still have the disadvantages of poor mechanical properties, single functions, and slow response speeds, which greatly limit their applications. In recent years scientists have attempted to improve the performance of environmentally responsive materials through nanotechnology. Wearable sensor technology is critical to achieving personalized medicine by continuously monitoring personal health. Physiological information can be non-invasively monitored. Previously reported sweat-based and other non-invasive biosensors can only monitor a single analyte at a time, or lack on-site signal processing circuitry and sensor calibration mechanisms to accurately analyze physiological status. The complexity of sweat secretion, simultaneous and multiple screening of target biomarkers is crucial, and comprehensive system integration is required to ensure the accuracy of the measurement. Provides mechanically flexible and fully integrated (ie, no external analysis is required) sensor arrays for multiple in situ perspiration analysis, simultaneously and selectively measuring sweat metabolites (eg, glucose and lactic acid) and electrolytes (eg, sodium and potassium) ions ), as well as the skin temperature (in response to calibrated sensors). Combining skin-based plastic-based sensors with silicon integrated circuits mounted on flexible circuit boards enables complex signal processing to bridge signal transduction, conditioning (amplification and filtering) in wearable biosensors Technical gap between processing and wireless transmission. Due to their respective inherent limitations, this application cannot be implemented using one of these techniques alone. The wearable system is used to measure the detailed sweat distribution of human subjects engaged in long-term indoor and outdoor physical activity and to perform real-time assessment of the subject's physiological state. The platform enables a wide range of personalized diagnostic and physiological monitoring applications. Therefore, while pursuing high-performance goals, the composition and structure design are given to their environmental response functions, and further integration of multi-function sensor devices to build a class of intelligent composite sensing detection systems. This paper summarizes the latest 10 research results of flexible physical or chemical sensors, including top journals such as Nature, Nat.Nanotechnol., AdvancedMaterials, MaterialsToday, Sci.Adv., as shown in Figure 1.
Figure 1 Journal Distribution
[Literature Reading]
1.Nature: Skin-like electronic device based on intrinsic stretchable transistor array scalable manufacturing process
Recently, Stanford University’s research team Bao Zhennan developed a fabrication process that can achieve high yield and uniformity of device performance for different intrinsic stretchable materials, and achieved an intrinsic stretchable polymer transistor array with a transistor density of 347/cm2. This is the highest density so far reported in all flexible stretchable transistor arrays. The array has an average carrier mobility comparable to that of amorphous silicon and only slightly changed after 1000 100% strain cycling tests. At the same time, there is no current-voltage hysteresis. Based on the above manufacturing process, the team has for the first time developed a skin-like stretchable integrated circuit element, such as a stretchable tactile circuit integrated with an active array and a sensor array, which can be adhered to the surface of human skin, allowing the flexible electronic device to be worn or Use more comfortable. The process it develops provides a versatile processing platform for the incorporation of other intrinsically stretchable polymer materials, making it possible to manufacture next-generation stretchable skin-like electronic devices.
2. Nat.Nanotechnol.: Graphene-based non-invasive, transdermal glucose monitoring with pathway selectivity and specificity
In the world, the incidence of diabetes is increasing, and the monitoring of blood glucose concentration in the human body becomes the basic guarantee for the care of patients with diabetes. At present, the main blood glucose monitoring method is achieved through the invasive blood collection of the fingers. This method inevitably brings certain pain and discomfort. The recently developed implantable microneedle sensors cannot be applied to most type 2 Diabetic patients. Thus, as of now, no needle-free method for monitoring blood glucose in diabetic patients has been reported. Recently, Professor Adelina Ilie of the University of Bath in the United Kingdom has designed and constructed a new in vivo glucose monitoring system. This system collects glucose from the tissue fluid of the hair follicles in the skin to achieve non-invasive glucose monitoring for the development of diabetic patients. Non-invasive blood glucose monitoring is of great value. The study also found that the system can continuously monitor blood glucose concentrations in the human body.
3.Adv.Funct.Mater.: A sensor with an opposite resistance response to normal-tangential force. Highly sensitive artificial skin
In order to be compatible with the external environment and attachable to 3D structures, wearable electronic skin requirements are flexible and stretchable. In order to achieve this goal, a flexible electronic skin with versatility has been developed, in which the development of the flexible force sensor is the fastest, because of its great application in smart terminals. For real detection, it is very important to realize real-time detection and differentiation of normal skin pressure and tangential friction force. Compared to current flexible pressure sensors or pressure-strain sensors, the research on the normal and tangential forces to detect electronic skin is very limited. There are three challenges for the development of this kind of electronic skin: (1) to realize the three-direction force detection of the electronic skin; (2) to realize the normal and tangential differentiation of different types of forces; (3) the simple structure can be prepared on a large scale. Here, researchers have created a new fully-flexible and multi-directional tensile force sensor using porous carbon nanotubes (CNTs)/graphene oxide (GO) @ polydimethylsiloxane (PDMS) layers. This unique electronic skin has good stability and high sensitivity (the highest response factor of the sensor to tangential friction is up to 2.26). In addition, the resistance of pressure and friction is opposite, and real-time detection and electrical signal discrimination between pressure and friction are realized. Recently, Associate Professor Song Yuanqiang and Professor Zhang Huaiwu of the University of Electronic Science and Technology of China and Professor Wei Weihua of the Harbin Institute of Technology (the co-corresponding author) have jointly developed a flexible electronic skin that can sense pressure and friction at the same time. Researchers prepared electronic skin based on CNTs/GO@PDMS composite three-dimensional conductive network by preparing special graphene-coated sodium chloride (GO@NaCl) powder as a porogen-assisted self-assembly process. The electronic skin can respond to both longitudinal and tangential friction forces, and the pressure and friction causes the resistance to change in the opposite direction. The electronic skin has particularly excellent sensitivity to friction (at a pressure of 1 KPa, the friction sensitivity factor is as high as 2.26). In the functional applications, the manufactured electronic skin can realize the real-time detection of wrist pulse, distinguish different surface roughness, detect human breath, and sense the air vibration brought by music.
4.AdvancedMaterials: Stretchable tribological electro-optic smart skin for tactile and gesture sensing
Smart skin, as a medium between a bionic robot and the external environment, requires stretchability and tactile sensing characteristics as well as the ability to measure a variety of external mechanical stimuli. In recent years, a variety of smart skins based on pressure sensors have been developed for use in tactile sensing, but due to the lack of stretchability and lateral stretch sensing characteristics, the functions and applications of these artificially intelligent skins have been greatly limited. In addition, some animal skins can communicate and camouflage by changing the color and luminous intensity, so having adjustable optical properties is also of great significance for smart skin. The scientific research team led by Zhang Chi, a researcher of the Beijing Institute of Nano Energy and Systems, Chinese Academy of Sciences, and a research team led by Academician Wang Zhonglin have developed a stretchable triboelectric electro-optic smart skin (STPS) that provides multi-dimensional tactile and gesture sensing for manipulators. STPS is based on a grating structure film with bionic skin folds, which can exhibit tunable aggregation-induced luminescence (AIE) at different transverse tensile strains. At the same time, it can also be used as a friction nano-generator (TENG), the open circuit voltage is used for longitudinal pressure sensing, and the pressure sensing characteristics remain stable under different tension conditions. By integrating the STPS into the manipulator as a conformal overlay, the STPS exhibits multi-dimensional tactile sensing and gesture translation features. This multi-functional sensing terminal coupled with triboelectric and optical excitation will have a wide range of application prospects in human-computer interaction, software robots and artificial intelligence.
5.Adv.Funct.Mater.: A self-absorbing tactile electronic skin that monitors human motion
The skin, as the largest human organ, plays an important role in the interaction between the human body and the external environment. With the increasing demand for health monitoring and human-computer interaction, the sensing performance of high-sensitivity, multi-functional artificial skin mimicking human skin has attracted worldwide interest. Piezoresistive, piezoelectric, frictional, and capacitive electronic skins have been developed so far. Among them, the piezoresistive sensor is expected to become the most promising electronic skin due to its simple preparation, high sensitivity and low cost advantages. Recently, in order to simulate the function of human skin, more work has been devoted to the development of multifunctional piezoresistive electronic skin. So far, these tasks have focused on the sensory properties of the skin and have neglected other skin functions. In particular, the complex structure of the skin has the function of protecting the human body against external injuries. Here, researchers implanted silver nanowires between PET and composite polymers to produce an electronic skin with multiple sensing and protection functions. Associate Professor Xuan Shouhu of the University of Science and Technology of China and Professor Yin Guansheng of Chang'an University (co-corresponding author) have constructed an energy-absorbing protection and multi-sensor sensing characteristics by assembling Ag nanowires, PET films, and SST/PDMS substrates. Electronic skin. This highly damped electronic skin can counteract the 720 to 400N impact force and can also detect human motion.
6.Adv.Mater.: Azimuth mechanical metamaterials are used to enhance the sensitivity of tensile strain sensors.
Stretchable strain sensors play a key role in wearable devices, soft robots, electronic skin, and the Internet of Things. However, these applications often require the detection of subtle strains under a wide variety of strains, and the low sensitivity limits their further development. This is mainly due to the Poisson effect of the conventional strain sensors, ie the tensile elastomer substrate is stretched in the longitudinal direction and compressed in the transverse direction. In stretchable strain sensors, stretching separates the active material and contributes to sensitivity, while Poisson compression squeezes the active material together, essentially limiting sensitivity. Therefore, adjusting and reducing the conventional transverse Poisson compression under tension is a key issue to enhance the sensitivity of the strain sensor. Recently, Prof. Chen Xiaodong of Nanyang Technological University and Liu Jianjian of A*Star published an article titled “Auxetic Mechanical metamaterials to Enhancing Sensitivity of Stretchable Strain Sensorsâ€. The authors used the Poisson's ratio of the negative structure of auxetic mechanical metamaterials to allow 2D stretching in both directions. , Embed it into stretchable strain sensors, thereby significantly increasing the sensitivity of strain sensors. Compared to traditional sensors, the sensitivity is increased by 24 times.
7.Sci.Adv.: skin-like flexible electronic device for medical grade non-invasive blood glucose monitoring
Diabetes has become a major chronic disease that threatens the health and life of modern people. In 2015, there were more than 400 million diabetic patients in the world. The number of diabetic patients in China exceeded 100 million, ranking the first in the world. The method of measuring blood glucose by taking blood with a “tie finger†has a certain degree of pain, affects the quality of life of diabetic patients and long-term compliance with self-monitoring. The current non-invasive continuous blood glucose monitoring method cannot directly measure glucose in the blood, and has not yet broken through on key issues such as accuracy, convenience, and complete non-invasiveness. Recently, Prof. Xue Feng (Corresponding author) from Tsinghua University published an article on Sci.Adv. on non-invasive blood glucose monitoring. This work uses a skin-like flexible sensing technology to establish a new non-invasive blood glucose measurement medical method, which provides a new way to solve the non-invasive blood glucose dynamic continuous monitoring, achieves a medical sense of non-invasive blood glucose measurement on the human skin surface, and has a medical grade Accuracy. Related content has been recommended by the Science Advances Press Package Team to internationally renowned media such as The New York Times, The Wall Street Journal and The Economist. On December 21st, IEEESpectrum, the flagship publication of the International Institute of Electrical and Electronics Engineers (IEEE), took the lead in this paper, and researchers from Purdue University and the Juvenile Diabetes Research Foundation (JDRF) Give a high evaluation. Professor Feng Xue’s research team has combined many years of experience in the development of flexible electronic devices to develop electroless two-channel non-invasive blood glucose measurement methods based on the principle of mechanics-chemistry coupling, utilizing flexible electronic devices that can be naturally attached to the human body. The surface of the skin is applied with an electric field that does not cause adverse skin reactions. The osmotic pressure of the tissue fluid is changed by iontophoresis to regulate the balance between blood and tissue fluid permeation and reabsorption, and the glucose in the blood vessel is driven to flow to the skin surface actively and directionally according to the design path. A skin-like biosensor with four functional layers was prepared on a 1.2 micron thick film based on the principle of mechanics. The nano-thickness electron mediator electrochemical deposition is realized by preparing the device surface microstructure, and the multi-layer ultrathin biosensor is peeled off non-destructively from the prepared substrate using a bionic droplet transfer method based on liquid surface tension and evaporation capillary force. Next, a skin-like flexible biosensor with a total thickness of only 3.8 μm was prepared.
8.Adv.Mater.: Self-driven pulse sensor for diagnosis of cardiovascular disease
Cardiovascular disease is one of the diseases that currently cause the highest mortality in the world. Patients with cardiovascular disease have long suffered from fear and torture. Fortunately, at present, 90% of cardiovascular diseases can be prevented through long-term detection of physiological signals related to the cardiovascular system. At present, the quality and performance of the devices used for in-situ monitoring of physiological signals are uneven, and although a certain effect can be achieved, the equipment cannot be used for a long time and the power supply system needs to be periodically replaced. In particular, the reduction in power supply caused by the miniaturization of equipment has made the contradiction between sensitivity and power consumption even more prominent. Compared to the current large number of research efforts focused on the search for a balance between power consumption and sensitivity, self-driven active sensing technology has provided a new solution to this contradiction. It can directly convert mechanical vibration signals into electricity. The signal thus solves the contradiction between power consumption and sensitivity, realizing self-driven sensing without power consumption and high sensitivity. A joint research team led by Li Zhou (Corresponding author) and Academician Wang Zhonglin (Corresponding author) of the Beijing Institute of Nano Energy and Systems, Chinese Academy of Sciences, and two cardiovascular disease experts from Beijing Anzhen Hospital and Chaoyang Hospital Fan Yifan (corresponding author) and Sun Guanglong Carried out research work and jointly developed a self-driven ultra-sensitive pulse sensor (SUPS) that can transmit Bluetooth without signal amplification and alert and diagnose cardiovascular diseases. SUPS is an active sensor based on frictional power generation and can output a voltage of 1.52V. It has a very high peak signal-to-noise ratio (45dB), which is 10 times that of medical photoelectric sensors. It still has good performance after 10 million cycles of operation. Output characteristics, and the preparation cost is very low, only 1/5 of medical photoelectric sensors. Compared with pulse sensors such as PPG (photoelectric pulse sensor) and PPT (piezoelectric pulse sensor) that require power supply, SUPS can obtain more detailed pulse wave signals. The pulse waveform signal output by the SUPS is proportional to the second derivative of the signal acquired by the conventional device, which allows us to easily analyze the pulse signal without additional complicated circuit design or logical operation. The SUPS has a high output voltage and can be integrated with a Bluetooth chip without a signal amplifier, enabling wireless transmission of pulse signals and visual display and analysis on smartphones/computers. Using this pulse sensor system, the researchers performed comparative tests on healthy adult patients and a series of patient groups. The successful diagnosis of arrhythmia (atrial fibrillation) and differential diagnosis of coronary heart disease and atrial septal defect were successfully achieved. . SUPS is expected to achieve self-driven wearable intelligent mobile diagnostics for cardiovascular disease in the future.
9.Nat.Nanotech.: A multi-functional, two-photon nanostructure designed by Longtail Glasswing Butterfly for medical devices
According to the survey, it is estimated that 8-10% of Americans (5-6% in other developed countries) need to rely on implanted medical equipment to maintain their physical functions during their lifetime. As a result, efforts to develop medical implant technology have been increasing. However, one of the main challenges to these efforts is to require multiple functions within a strictly limited range, while at the same time it must be ensured that it is acceptable in terms of in vivo performance and reliability performance. The inspiration for multi-functional surface engineering is usually from the natural world, it has a large number of nanostructures, with a wide range of ideal characteristics. In nature, many living organisms have photonic nanostructures that provide color and many other functions for survival. Although these structures have been actively studied and replicated in the laboratory, it is not yet clear whether they can be used for biomedical applications. Recently, Prof. Hyuck Choo of the California Institute of Technology and Professor David Sretavan of the University of California (co-corresponding author) reported a transparent two-photon nanostructure inspired by the long-tailed glass butterfly (Chorinea faunus). It uses the intraocular pressure (IOP) sensor in the body. The phase separation of the two immiscible polymers (polymethyl methacrylate and polystyrene) produces nanostructure features on the Si3N4 substrate. The resulting film has good keratinous white light transmission, strong hydrophilicity and anti-biological activity, preventing protein, bacteria and eukaryotic cell adhesion. Moreover, they used the prepared photonic film as an optical sensing element to develop a miniature implantable IOP sensor. Finally, in vivo testing in New Zealand white rabbits showed that the prepared device reduced the average measurement bias of IOP without evidence of inflammation.
10.Nature Communications: Stretchable Extended Multifunctional Integrated Electronic Skin
Human skin is an active, very sensitive and highly elastic sensory organ, and it is mainly responsible for protecting the body, perspiration, temperature regulation, perception of cold and heat, and stress. The body somatosensory system can convert external environmental stimuli into electrical pulse signals through sensors in the skin, such as tactile sensation, temperature, and pain sensation, and conducts through the nerve pathways to the nerve center so that the skin acquires sensory functions such as tactile sensation and pain sensation. Based on this multi-functional biological model of skin, scientists have developed a new discipline of research - touch-sensitive electronics (commonly known as "electronic skin", Electronickins, E-skin) that mimics skin's sensory functions such as touch, temperature perception, etc. Features. At present, electronic skin is a sensor or array with pressure, temperature, or other stimuli generated on a flexible or elastic substrate. It can sense a variety of physical, chemical, and biological signals in the surrounding environment and will help develop new human-machine interfaces. , intelligent robots, bionic artificial limbs and other intelligent systems. The important development trend of electronic skin is: multi-functional and simultaneous monitoring of multiple stimuli. Recently, research team Pan Caofeng and researcher Wang Zhonglin from the Beijing Institute of Nano Energy and Systems, Chinese Academy of Sciences, reported on a flexible and stretchable multi-function integrated sensor array that successfully extended the detection capability of electronic skin to 7 types. The real-time simultaneous monitoring of various external stimuli such as temperature, humidity, ultraviolet light, magnetism, strain, pressure and proximity is realized.
Summary and outlook
With the rapid development of society and economy, many fields require higher and higher requirements for the materials used. Taking into account the majority of wearable systems, healthcare electronics and laboratory chip testing tools can be exposed to arbitrary curved interfaces. The sensor's flexibility is crucial to improve its interaction with the target system and improve reliability and stability. Therefore, flexible sensors have great promise for innovative applications such as medicine, healthcare, environment and biology. Therefore, this topic will take the current popular graphene-based flexible sensor field as the starting point, and in pursuit of high-performance targets, it will give its characteristic signal response function through its composition and structural design. However, there are still many problems in the application of traditional sensing materials or environmental-responsive materials. There are mainly the following points:
(1) At present, there are few flexible substrates for preparing sensor devices, and the electrical and mechanical properties cannot meet the requirements for use.
(2) The interface of the multi-layered sensor device is unstable in the flexible state, which affects the performance of the sensor device.
(3) Single-sensor devices are often unable to meet the actual requirements, and have a single function and a low degree of intelligence.
Plug-In Connecting Terminals,Insulated Spade Terminals,Cable Connector Double Spade Terminals,Vinyl-Insulated Locking Spade Terminals
Taixing Longyi Terminals Co.,Ltd. , https://www.longyicopperlugs.com