Why is it so difficult to shake hands with robots? Babies can draw lots at the age of one, but teaching a robot to grasp is something that hundreds of top tier papers cannot explain clearly. Scientists tell us that compared to playing chess like a human, speaking like a human, or walking like a human, having a robot pick up a balloon or hold a glass is a more difficult task. Ten years ago, there was a saying in our circle: 'Don't shake hands with robots,' "said Shen Guozhen, director of the Institute of Flexible Electronic Devices and Intelligent Manufacturing at Beijing Institute of Technology. Why do you say that? What is missing from a robot that doesn't know how to shake hands and how to interact with the world? Without skin, it's really different from before - "In the past, robots didn't have touch, couldn't control force, didn't know when to release their hand when shaking hands with people, and could accidentally crush bones in the human hand." Shen Guozhen's answer revealed a major problem in robot research - robots were missing one human organ, and the largest one was the skin. Without skin, robots would find it difficult to have developed tactile abilities. One of the classic robot characters in film history, Edward Scissorhands, who accidentally exerts force to injure people, is still not uncommon in robot laboratories today. Therefore, we have been talking about robots writing essays and playing chess, but we have not yet heard of robots skillfully completing household chores. Touch is actually a combination of various perceptual information: the location of contact, the magnitude and direction of contact force, the temperature, texture, and hardness of the object in contact (or even the object not in contact)... Our skin can capture these subtle clues and transmit them to the brain, triggering many of our habitual reactions and actions. It can be said that skin is not just a layer of nearly 2 square meters of attachment on the surface of the body, but also a communication link and interaction method between people and the surrounding world. So, how about adding a skin to the robot? Can robots perceive and adapt to their environment like humans? A robotic arm equipped with a biomimetic 3D electronic skin interacts with a human hand to create an electronic skin. Of course, not all robots in the movie are like Edward. The protagonist of the science fiction movie 'Alita', the robot Alita, although slim, is a 'hexagonal warrior'. Her combat power comes from a body of "black technology", including electronic skin that is more sensitive to touch than humans. Yes, electronic skin. Enabling robots to fully perceive their body and surrounding environment, electronic skin has become an important research field in robotics today. With the help of electronic skin, robots can have a sense of touch and more fully and accurately read pressure signals in the environment, making their actions more flexible and effective. Generally speaking, current robots lack precise force feedback for objects, making it difficult to grasp and manipulate small or soft objects accurately. Electronic skin, on the other hand, can endow future robots with a pair of "skillful hands", making it possible to perform high-precision surgeries without any problem. What exactly is an electronic skin? Shen Guozhen introduced that human skin is composed of epidermis, dermis, and subcutaneous tissue, and electronic skin is also a similar "sandwich" structure, consisting of electrode materials, active materials, and flexible substrates. The electrode material serves as an electrical connection layer located on both sides of the active material, receiving and transmitting electrical signals; The function of active materials is to convert environmental stimuli into detectable electrical signals; The flexible substrate is responsible for supporting the electronic skin and bonding it to the robot body. What issues must be addressed when developing an electronic skin? The first and foremost issue is the softness of materials. The key to electronic skins lies in the word 'soft'. The material that can be used as skin must be flexible and stretchable, rather than rigid and brittle. How is it possible to 'bend the finger'? There are currently three directions of exploration in the scientific community. The first approach focuses on physical flexibility and strives to develop materials with smaller scales. For example, soft and highly biocompatible nano silicon can be used as a biochemical sensor to achieve skin function to a certain extent. The second approach relies on structural flexibility. Efforts are being made to develop various novel mechanical structures of metals and other materials, such as springs, coils, and serpents, to transform traditional hard materials into new materials with good tensile and bending capabilities. Some scientists are attempting to break through intrinsic flexibility by altering the properties of polymer materials through polymer engineering, giving them high tensile properties and even self-healing capabilities. To develop electronic skins, we still need to focus on the perception function. Sensing is the foundation of machine perception of the environment, sensing pressure and temperature, judging different objects touched, and distinguishing whether the object in hand is a peach or an egg, all of which require sensors. Tactile sensors need to fully capture various surface characteristics of objects in contact, with particularly high requirements for sensing sensitivity. The flexible and stretchable multifunctional electronic skin developed by Shen Guozhen's team can be used for real-time monitoring of human physiological signals. In addition, how to efficiently transmit the signals captured by sensors is also a problem. The key is how to minimize signal loss during transmission to the robot's brain? Do we also have a set of electronic skins? In fact, electronic skins are not just the next generation of equipment for robots, we humans ourselves are also 'worth having'. In today's rapidly developing virtual reality technology, electronic skins may be an important tool for humans to explore the metaverse. In the virtual world, electronic skin can maximize the restoration of touch, not only allowing people to "touch" virtual objects almost realistically, but also restoring the feelings brought by breeze, water flow, and flames, greatly enhancing immersion and realism. In addition, for burn patients and amputees, electronic skin can help them regain touch and continue to enjoy a better life. What can electronic skin help for ordinary people with physical and mental health? It can serve as a human health monitoring device. Electronic skin comes into direct contact with the human body and can directly measure real-time body data (such as heart rate, body temperature, blood sugar, blood pressure) through high-precision sensors, which is equivalent to a highly precise 'health wristband'. Shen Guozhen said that such technology has matured and products will gradually enter the market. In fact, scientists have a bolder idea - can the functions of smartphones be integrated into electronic skins? If the sensors of the electronic skin are sensitive enough, the circuit is smooth, and the performance is stable, wouldn't it be natural to send and receive messages and make calls by "clicking" on different positions of the electronic skin? Perhaps by then, we can really leave our phones behind and go out light. (New Society)