Interference against liquids and a flexible strain sensor preparing new policy bacterial adhesion

Promoting research and development of artificial intelligence strain sensors, microelectromechanical systems skin, the development of implantable biological field sensors and biological diagnostics. To further promote the practical application of the strain sensors, considering its stability during use is particularly important. Especially in some harsh environments such as water, microorganisms, acidic, basic conditions can lead to device conductivity and electronic sensing instability, thus affecting the performance of the strain sensor and shorten its life. For example, a microorganism in an aqueous environment the surface of bacteria attached to the sensor, corrosion of the conductive layer, so that the interference pathway. Water can penetrate into the pathway, interference sensing performance. In order to avoid the environmental impact of liquid sensor performance, extending its life, to build a super-hydrophobic surface of the sensor is a good strategy. Since the area of ​​contact between the liquid and super-hydrophobic surface is very small, the conductive layer difficult to penetrate the liquid sensor. But previously reported superhydrophobic sensor focused on the design of ultra-hydrophobic strain sensor function, and how the design of liquid anti-interference strain sensor and studies the mechanism of liquid anti-interference, has not been reported. Recently, Guangzhou University Professor Lin Jingfu , Beijing Normal University, Professor Liu Nan and the University of Tennessee [123 ] Guo Zhanhu Associate Professor cooperation proposed a new strategies interference against liquids and a flexible strain sensor bacterial adhesion was . of a fluorine-containing unique micro / nano structure by constructing multilevel F / Ag / MWCNG / G-PDMS (FAMG) strain sensors, the liquid in the Cassie-Baxter state wetted surface of the sensor, performance superhydrophobic resistance and self-cleaning function. The surplus stable sensor performance liquid resistant strain sensing interfering in tests, while having high sensitivity, wide strain range, the advantages of quick response time. The authors also explored in depth Cassie-Baxter state wetting liquid resistant strain sensing interference in the action of the strain sensor and high sensitivity, wide strain range of reasons. Further, the sensor exhibits excellent underwater superhydrophobic and oleophobic, so that it has good resistance to interference and antibacterial liquid adhesive properties. Finally, the sensor is applied to an electronic EagleWings in outdoor sports and artificial rainfall monitoring, and monitoring of human motion a complex environment, indicating its potential applications in the field of wearable electronic devices. The work entitled \”Anti-liquid-Interfering andBacterially Antiadhesive Strategy for Highly Stretchable and UltrasensitiveStrain Sensors Based on Cassie-Baxter Wetting State\” published in \” Advanced Functional Materials \” (Adv. Funct. Mater. 2020,2000398) on.

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FIG. Preparation strategy liquid resistant strain sensor interferenceOn the first conventional MWCNT / G-PDMS strain sensor was prepared, and added dropwise to explore different droplet impact on the sensor device surface resistance. The results show that when the liquid is placed on the surface of the sensor, the resistance is reduced. Although such graphene and MWCNT MWCNT / G-PDMS strain sensor surface having a certain hydrophobicity, but in this case, the droplets on the strain sensor can be considered in Wenzel wet state, the conductive layer is present between the droplet and the strain sensor is more a large contact area. And the liquid will gradually penetrate cracks generated drawing process, with the increase in the amount of stretching, the contact angle is significantly reduced. Thus, when the droplets on the sensor surface, the resistance decreases, thus affecting the performance of the sensor. Thus, based on OF MWCNT / G-PDMS, by constructing a fluorine-containing silver nanoparticles and micro / nano multi-level structure (F / Ag / MWCNG / G-PDMS (FAMG)), FAMG strain sensor is designed such that droplets Cassie-Baxter sensor surface was wet state. In this case, the droplets floating on an air layer can be prevented from contacting the droplets with the conductive layer, no liquid penetrates into the conductive film impact resistance, resistance to the liquid in order to achieve interference. At the same time, the use of APTESAs the conductive layer between the substrate and the adhesive between adjacent conductive layers, such that the intermediate separation layer is formed terminal cracking and slippage, thereby enabling the strain sensor FAMG obtain high sensitivity and a wide strain range.

FIG 2.FAMG strain sensor sensing fluid properties and resistance to interferenceFAMG strain sensing the strain sensor and anti-interference performance liquid as shown in FIG. OF different droplet by dropping the sensor surface, which is resistant to liquids investigated interference. The results show, liquid smaller influence on the sensor resistance, indicating that the sensor has a good anti-interference performance liquid. At the same time, this structure is also constructed such that the adhesive layer with ultra-high sensitivity of the sensor (GF = 2059, 160% -180% strain), and ultra-fast response time (150 ms). By cycle test was found, the sensor exhibits high repeatability and good cycle stability, so it has great potential in practical applications.

FIG 3.FAMG Strain sensor against liquids and interference sensing mechanismTo further elucidate the mechanism of interference in the sensor liquid resistant strain sensing process, by the establishment of transmission strain feeling model and corresponding results of SEM analysis. Sensor structure model shown in Figure 3a, including the silicone and the substrate surface due to the action of hydroxyl closely APTES and bottom, in close connection with APTES layer intermediate layer (APTES / MWCNT / G) is formed adjacent MWCNT / G, inviscid multi-level structure of the outer cover layer junction MWCNT / G and the core layer F / Ag / MWCNT / G. When no strain is applied, rendering the sensor surface without cracks of a wrinkled surface. Due to the low surface energy fluorocarbon chains synergistically with Ag / MWCNT / G micro / nano structures, wrinkles can be seen the gap filled with a layer of an air layer, the strain sensor in this case FAMG superhydrophobic Cassie-Baxter wet state , droplets suspended in the air layer, the barrier contact with the conductive layer of the droplets, the liquid can not penetrate into the conductive layer. When FAMG stretched to 60% strain sensor, the sensor surface microcracks, but graphene microbridge and the intermediate separation layer carbon nanotubes because multi-walled slip, the core layer overlap each other, the conductive path remains connected. When FAMStrain G increased 110%, most of the core layer are not bonded completely separated graphene overlap, despite the presence of crack bridging the gap, some of MWCNTs began to separate. With further stretching, MWCNTs micro bridge gradually reduced. The intermediate separating layer (APTES / MWCNT / G) due to the increase of the stretching occurs during the traction slip, so that the graphene bonded overlapping separation gives rapid crack propagation, so that a rapid increase in resistance. Since the strain sensor FAMG Cassie-Baxter surface remains wet state, although a lot of pressure is applied, but the liquid did not interfere with the sensor. Accordingly, the resistance change of the strain sensor FAMG by increasing the number of cracks and crack dominated area. Anti-interference performance liquid while the sensor is closely related to the superhydrophobic Cassie -Baxter wet state. To demonstrate the strain sensor FAMG potential applications in the flexible wearable electronic device, of which was used to monitor body motion (FIG. 4) to monitor movement of electrons under the wings of the eagle and outdoor environment and the complexity of artificial rainfall. The results show that, when used in the electron motion eagle wings artificial rain outdoors and monitoring, sensor indicates stable resistance change, which showed stable performance. By detecting movement of the body while at conventional bacterial droplets into the case, the results showed that the sensor has good resistance to liquids and interfere with bacterial adhesion properties, so that it is applied to complex environments having a large fine real-time sensing of strenuous exercise and the potential applications.

Application of wearable FAMG strain sensor 4. FIG liquid resistant bacterial adhesion and interferenceIn summary, the proposed interference resistance and a process for preparing the liquid flexible wearable bacterial adhesion strain sensor new strategy, and confirmed its potential applications in complex environments. The liquid sensor is not more interference and with high sensitivity and stability. Meanwhile, the sensor exhibits excellent superhydrophobic and underwater oleophobic, plays an important role in preventing bacterial adhesion and interference liquid sensing strain. As a wearable electronic device successfully used artificial rain droplets and bacteria in motion a series of human and electronic monitoring of birds. Thus, such a liquid resistant bacterial adhesion and interference strategy provides a new way to design a flexible environment for complex, wearable strain sensor. Original link: https: // oWhere is it library.Wiley.com/do i / 10.1002 / A unilateral .202000398