Scientists used “living human skin” to make a face for the robot. It smiled and made me cry.

Recently, Japanese scientists made a "face" for a robot that can smile, move and have wrinkles.

Many netizens thought of "Terminator" after seeing it. After all, the smile in the picture does look like Schwarzenegger's performance in "Terminator".

This is actually not from a science fiction movie, but a "robot face" created by the team of Professor Shoji Takeuchi and Michio Kawai of the University of Tokyo in Japan using living human skin cell tissue.

And this face is most likely to be used on people first.

How to put "human skin" on a robot

For more than a decade, robotics researchers have been experimenting with various materials, hoping to find one that can protect the complex machinery of robots while being soft and light enough, but progress has been slow.

Although the current silicone skin of robots can imitate human skin to a certain extent, the details are still not enough. Not only is it difficult to achieve appropriate adhesion to the machine, but once the surface is scratched, it will often affect the mechanical function. operation, and this can easily lead directly to the "uncanny valley effect".

How can we talk about serving people if we see a robot that scares people?

▲ Uncanny Valley Effect – When humanoid robots or simulation images become very realistic but not completely realistic, people will feel strong uneasiness and disgust

Japanese scientist Shoji Takeuchi described this method in his paper "Perforation-type anchors inspired by skin ligament for robotic face covered with living skin (Perforation-type anchors inspired by skin ligament for robotic face covered with living skin)", Because the skin it generates is a mixture of human skin cells, it looks and feels very similar to human skin and solves the problem of robot skin fixation to a large extent.

In humans, there is a huge ligament network that fixes the skin to the underlying muscles and tissues. The researchers followed this idea and designed a V-shaped perforated structure. Professor Takeuchi said:

By mimicking the ligamentous structure of human skin and using specially designed V-shaped perforations in the solid material, we discovered a way to combine artificial skin with mechanical structural structures. The design of the V-shaped perforations mimics the structure of human skin ligaments, allowing the skin to move with the robot's mechanical parts without tearing or peeling off.

▲ Left: Human facial structure Right: Robot facial structure

The researchers also tested and evaluated the ability of this perforated anchor to fix skin tissue through a series of experiments:

First, to demonstrate the versatility of perforated anchors on 3D objects covering complex contours, the researchers fabricated a 3D facial device covered with skin equivalents.

A dermal equivalent fixed on the anchor was formed by pouring gel dermal solution and incubating for 7 days. In order to imitate the human facial structure, they also set up some small holes in the robot's face and filled them with a large amount of gel containing elastic materials.

Next, artificial epidermal keratinocytes were inoculated on the dermis and cultured for 17 days, finally forming a robot skin with dermis and epidermis layers.

The study noted that uniform thickness of the collagen injection space is critical to achieve uniform coverage and found that skin equivalents varied in thickness in different contour areas.

Experiments have also shown that the use of perforated anchors is critical to secure skin equivalents, otherwise the tissue will separate due to contractile forces.

▲ During the culture process, tissue without anchors shrinks and cannot maintain its shape.

In order to verify the effect of perforated anchors in inhibiting skin shrinkage, the researchers produced devices with perforated anchors of different diameters (1mm, 3mm and 5mm), and injected collagen gel containing human normal skin fibroblasts into the device to form a dermis. equivalent, the shrinkage of the dermal equivalent was observed over a 7-day period.

The results show that:

  • The samples without anchors shrank by 84.5% within 7 days, while the samples with anchors shrank much less.
  • A 1 mm diameter anchor limits shrinkage to 33.6%.
  • A 3 mm diameter anchor further limits shrinkage to 26.3%.
  • At 5mm, the degree of shrinkage increased by 32.2%.

This may be because larger anchors occupy more surface area, causing the tissue to shrink farther toward the center.

▲The effect of different numbers of anchor points on inhibiting skin shrinkage

The researchers also evaluated the impact of the number of anchor points on anchoring performance through the finite element method (using computer simulation technology to evaluate and analyze the impact of the number of anchor points on anchoring performance). The results showed:

  • The greater the number of anchors, the more resistant the skin is to stretching forces.
  • When the anchor bolt is far away from the stress point, the skin will undergo significant displacement under a small force.

That is, areas with lower anchor density allow greater deformation but tend to cause concentrated loads on a single anchor. Conversely, a higher anchor density can provide stronger adhesion and lower deformation.

This demonstrates the potential utility of perforated anchors for selective actuation of facial skin, much like human facial muscles. In other words, the arrangement of different anchor density on the skin will become the key to the "expression" design on the skin.

In human emotional expression, facial skin is often driven to form expressions through the contraction of mimic muscles. On this skin, the researchers also controlled the skin thickness, anchor point density, anchor length and other factors to selectively deform the skin and recreate a smile similar to a human face.

▲Simulating robot facial drive

Why "skin" is so important

In fact, Professor Takeuchi has always advocated combining human biological tissue and mechanical materials to create robots with more anthropomorphic characteristics. he thinks:

Living skin is the ultimate solution for giving robots a biological look and feel.

In 2022, he and his team used collagen and dermal fibroblasts to create human-like dermal fingers.

The artificial "skin" created not only has good elasticity, but can also wrinkle and stretch with the movements of the fingers, giving people a very close feeling to real fingers.

And the skin also has a certain degree of repairability. The researchers cut a small incision on the "finger" and used a collagen dressing to wrap it. After leaving it in a petri dish for a week, the collagen could repair the skin to a certain extent.

After this experiment, Professor Takeuchi said:

We were struck by how well the skin tissue conformed to the surface of the robot.

In January this year, he also proposed to imitate human muscles to make robot legs, creating a mechanical structure biohybrid robot with machinery as bone and human tissue as skin and flesh.

Although today's artificial skin still seems a bit "scary", in fact, making robots more and more like humans is one of the important goals of humanoid robots.

This is mainly because humanoid robots can provide a more natural and friendly interaction experience by imitating humans in appearance, expressions and movements. This similarity makes humans feel more comfortable when interacting with robots, making it easier to accept and trust them. Takeuchi Shoji said:

Human-like faces and expressions improve communication and empathy in human-robot interactions, making robots more effective in healthcare, service and companionship.

For example, in many science fiction movies, realistic human skin has become the standard feature of humanoid robots. Even in "Liao Zhai", beautiful "painted skin" is an inevitable choice for ghosts to get close to humans.

Obviously, humans are naturally more likely to form emotional connections with similar faces and behavioral patterns, providing emotional support and companionship. By imitating human expressions, voices and body language, humanoid robots can more smoothly integrate into human work environments, use the same tools and equipment as humans, and even fill the roles of actors, models or art creators.

Wang Yifan, an assistant professor at the School of Mechanical and Aerospace Engineering at Nanyang Technological University in Singapore, said this skin combination gives biohybrid robots the potential to feel:

This could create opportunities for robots to sense humans and interact with them safely.

▲ The humanoid robot in the movie "Ex Machina"

However, although the experiment was successful, there is still a long way to go before it can be used on robots. Professor Takeuchi said:

First, we need to improve the durability and longevity of cultured skin when applied to robots, specifically addressing issues related to nutrition and moisture supply. This may involve the development of integrated blood vessels or other perfusion systems within the skin. Second, it is critical to increase the mechanical strength of the skin to match that of natural human skin. This requires optimizing the collagen structure and concentration within cultured skin.

He also pointed out that to truly function, artificial skin must ultimately be able to convey sensory information such as temperature and touch to the robot wearing it, and this is the next research goal of Professor Takeuchi. He said:

Our goal is to create skin that closely mimics the functions of real skin by gradually building up basic components such as blood vessels, nerves, sweat glands, sebaceous glands, and hair follicles.

▲ Takeuchi Masaharu

It is worth mentioning that if the research on artificial skin is successful, it can not only be used in robot manufacturing, but also has great application potential in other fields, such as designing and making prostheses, treating burns, cosmetic sequelae, facial paralysis, etc. Michio Kawai express:

With the development of AI technology and several others, allowing robots to assume more roles, the functional requirements of robot skins are also changing.

In some experiments, researchers found that when robot skin maintains one shape for a long time, it can replicate the wrinkle generation process:

Skin models that recreate wrinkle formation could potentially be used in testing cosmetics and skin care products designed to prevent, delay or improve wrinkle formation.

This will undoubtedly play a huge role in researching and testing new cosmetics and skin care products.

This "skin" specially created for robots will most likely be used on humans first.

Obviously, there is still some controversy over whether this technology can help robots become more human-like, but it may be used in fields other than robots.

Isn't this another kind of success?

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