In the past 10 years, artificial skin research has made significant progress, but even the most effective self-healing materials still have major deficiencies. Some are not practical because they must be exposed to high temperatures. Some can heal at room temperature, but repairing the wound will change its mechanical or chemical structure, so it can only be used once. Most importantly, there has not been a self-healing material with good electrical conductivity.
Recently, a research team at Stanford University in the United States has developed the first synthetic material that has a sharp touch and can heal quickly and repeatedly at room temperature. This progress may lead to the emergence of smarter artificial limbs or more flexible self-repairing personal electronic products. The research results were published in the journal Nature & Nanotechnology on November 11.
Researchers have been trying to imitate the excellent properties of human skin, such as the tactile sensation of the skin (accurate information sent to the brain about pressure and temperature) and efficient self-healing ability. Professor Zhenan Bao and his team from the Department of Chemical Engineering at Stanford University successfully integrated the above two properties into a single synthetic material.
The team of Bao Zhenan successfully achieved the best of both worlds by mixing the two components-the self-healing ability of the plastic polymer and the conductivity of the metal. The plastic they use contains long-chain molecules linked by hydrogen bonds. These molecules are easy to break up. When they are reconnected, the hydrogen bonds can reorganize and restore the structure of the material.
The researchers added tiny metallic nickel particles to this elastic polymer to increase its mechanical strength. The nano-scale surface of nickel particles is rough, which is essential for the material to form conductivity. Each protruding edge accumulates an electric field, making it easier for current to travel from one particle to the next, thereby making the plastic polymer conductive.
The researchers tested the material's ability to recover from mechanical damage and electrical conductivity after damage. They took a thin strip of material and cut it in half. After putting it together and gently pressing it for a few seconds, the material can recover 75% of its original mechanical strength and conductivity; if pressed for 30 minutes, the recovery of the material's performance is close to 100%. More importantly, the same sample can be cut repeatedly in the same place. After 50 cuts and repairs, the flexibility and stretch of the sample are still intact.
The team also discussed the pressure-sensitive properties of the material. The process of electrons forming a current in the material is similar to jumping across a stream between stones. Nickel particles play the role of stones, and the distance between them determines how much energy an electron needs to jump from one stone to another. The twisting or pressing on the synthetic skin will change the distance between the nickel particles, which will change the difficulty of electron hopping. These subtle resistance changes can be converted into information that the skin is under pressure and tension. Researchers say the material can detect pressure changes caused by handshake.
Bao Zhenan said that the material is very sensitive to depression and flexion, so future prostheses will have better bending at the joints. Electrical equipment and wires covered with this material can also repair themselves, making electrical maintenance no longer difficult and expensive, especially in hard-to-reach places, such as building walls or vehicles. The research team's next goal is to make the material more transparent and more flexible, suitable for packaging and covering electronic devices or display screens.
Take a deep breath, close your eyes, the world has the freshest oxygen ... Yu Quan's "Deep Breath" is well known to us, but as the environmental problems become more and more serious, the haze sky also increases, PM2.5 PM10 and so on Vocabulary has also been mentioned more and more, and air purifiers have quickly become popular on the market with this "air quality" trend. Along with this, the air-clean brand has sprung up, and various technologies are dazzling. Which ones are indeed effective and which are just tasteless propaganda? How does the Air Purifier bother us to get rid of pollution? And look at the editors for you.
Analysis of air purifier
The critical value of PM2.5 content is 75 μg / m3
The pollutants in the air mainly include soot, total suspended particulates, inhalable particulates (PM2.5) and fine particulates (PM10). The smaller the diameter of the particulates, the deeper the part that can enter the respiratory tract. 10 micron diameter particles It is deposited in the upper respiratory tract, and particles below 2 microns can penetrate 100% into the bronchiole and alveoli.
1k-5k air purifier prices vary greatly
The air purifier products on the market not only have various functions, but also have prices ranging from thousand yuan to tens of thousands. The pricing of imported products is generally higher than that of domestic brands. Except for the core technology of many brands, the promotion of purification effects is similar, and consumers need to choose according to demand.
The air quality standard of 74 key cities is only 4.1%
According to the data of the press conference held by the State Council Information Office on June 4, according to the new "Ambient Air Quality Standards", the six pollutants SO2, NO2, PM10, PM2.5, CO and O3 were evaluated, 74 new standards In the first phase of monitoring and implementation, the proportion of cities that met the ambient air quality standards was only 4.1%, and the other 256 cities implemented the old air quality standards, and the proportion of cities that met the standards was 69.5%.
Air purifier sales increased by 90.5% compared with last year
According to a report recently released by the China Electronics and Information Industry Development Institute, due to the haze weather, air purifiers have become the most concerned home appliance products, with sales of nearly 2.4 million units nationwide last year, a year-on-year increase of 90.5%; retail The amount reached 5.6 billion yuan, a year-on-year increase of 105.9%.
HEPA filter needs to be replaced in March
The filter of the air purifier is the same as the filter of the water purifier, and it is not effective for a long time. After long-term use, the accumulation of dust on the surface of the filter will also cause the filter to gradually fail. Therefore, when the haze is more serious, the non-washable HEPA filter needs to be replaced every three months.
Merchants claim that the purification rate is more than 99% for the concept of stealing
99% or even 99.99% seems to have become a slogan for many air purifiers on the market. Many brands of products promote their high removal rate of PM2.5 and formaldehyde. In fact, this kind of publicity is more of a kind. The slogan of stealing the concept, the removal rate of 99% is the effect of the material itself on PM2.5 and formaldehyde, not the effect of actually running in space.
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