The hottest MIT has designed active materials that

MIT has designed "active materials" that can be used as new sensors

it is reported that MIT has designed a "active material" that can monitor chemicals in the environment or human body. At present, the potential of this material as a new sensor has been certified in a paper published in the proceedings of the National Academy of Sciences this week

it is understood that this "active material" is a hydrogel film implanted with living cells. This hydrogel film is tough, elastic and biocompatible. The implanted cells are genetically modified and will glow when they encounter specific chemicals

researchers found that the water rich environment of hydrogels is conducive to the maintenance of nutrients and the survival and activity of transgenic bacteria. As shown in the figure, when bacteria respond to specific chemicals, bacteria will emit light under the action of genes

the team used hydrogels implanted into cells to make a variety of wearable sensors, including a moth resistant rubber glove, which will shine when the fingertips touch the surface contaminated by chemicals. A bandage is also made, which will become shiny when applied to human skin stained with chemicals

"through this design, people can put different types of bacteria into the device to indicate toxins in the environment or diseases on the skin." Timothy Lu, associate professor of bioengineering and electrical engineering and computer science, said, "our results show the application potential of active materials and related devices."

inject life into materials

lu and his colleagues in MIT's synthetic biology team are specialized in biological circuit research, and gene recombination of biomass in living cells (such as E. coli) to make it work in an orderly manner, which is very similar to the logical steps in the circuit. Using this method, scientists can redesign cells to perform specific functions, such as sensing the presence of viruses and toxins and sending signals

however, most of these new transgenic cells can only survive in Petri dishes. Scientists can carefully control the various nutritional levels required to maintain cell activity in Petri dishes - and this environmental condition is extremely difficult to replicate into synthetic materials

"the primary challenge in manufacturing active materials is how to cultivate these living cells so that they can survive and perform certain functions." Lu said, "cultured cells need humidity, nutrition, and some also need oxygen. The second challenge is how to prevent them from losing from the material."

in response to these roadblocks, other researchers used freeze-dried chemical extracts from genetically engineered cells and combined them with paper to produce low-cost virus detection and diagnosis test paper. However, Lu believes that unlike living cells, the extract can maintain its function for a long time and has higher sensitivity in detecting pathogens

other research teams have inoculated cardiomyocytes onto rubber films to make soft, "live" actuators or robots. However, after repeated bending, these membrane materials may rupture, resulting in the leakage of living cells

vibrant cell host

Professor Zhao's team developed a new material hydrogel in MIT's active soft materials laboratory, which is a biocompatible material with high toughness and elasticity made of polymer and water, and may be an ideal choice for host living cells

in the past few years, the team has proposed a variety of hydrogel formulations. In their latest design, the water content is as high as 95%. Professor Zhao and Lu agreed that this aqueous material is very suitable for forming an environment to maintain the survival of living cells. The material is not easy to crack even after repeated stretching - this feature is very conducive to containing active cells

then, the researchers soaked the hydrogel/elastomer material in the nutrient solution to fill the hydrogel with nutrients, so as to ensure that the bacterial cells in it can survive for several days

in order to prove the potential of the material and because the technology that does not integrate the two is used, researchers first manufactured a piece of material with four independent narrow channels, each channel contains a kind of bacteria, each of which is designed to respond to different chemicals and emit green light. As a result, there is no doubt that the four channels were successfully lit when exposed to the corresponding chemicals of each bacterium

next, the team made the material into bandages or "active stickers", in which the patterned channels contain bacteria sensitive to rhamnose (a naturally occurring sugar). The researchers wiped the volunteers' wrists with cotton balls soaked in rhamnose, and then pasted the aqueous gel patch. The "active patch" responded to the skin contact and began to glow

finally, the researchers made a hydrogel/elastomer glove, and designed vortex channels at the fingertips, each channel filled with bacterial cells that respond to different chemicals. When pinching cotton balls impregnated with different compounds, each fingertip responds accordingly and emits a glow

the team also developed a theoretical model to help guide others in designing similar active materials and devices

"the theoretical model can help us design active devices more effectively." Zhao said, "it will tell you how thick the hydrogel layer should be, the distance between channels, how to make channel patterns, and how many bacteria to use."

Professor Zhao finally envisioned various products that may be made of active materials in the future, such as gloves for detecting signs of infection or disease, rubber soles lined with chemical sensing hydrogels, or bandages, patches, and even clothing

this study was partially supported by the Naval Research Office, the National Science Foundation and the National Institutes of health