Researchers design platypus-inspired multi-receptor bionic skin

Although engineers have developed increasingly advanced bio-inspired systems in recent decades, the sensing capabilities of these systems are generally far less advanced than those seen in humans and other animals.

The design and manufacture of more sophisticated sensors and artificial skins could further improve these systems, allowing them to accurately capture a wide range of sensory information from their environment.

Researchers from the Beijing Institute of Nanoenergy and Nanosystems and Tsinghua University have recently developed a new multi-receptor skin inspired by the sensory capabilities of the platypus, an intriguing animal that combines some physical characteristics of ducks, beavers and otters.

The team’s multi-receiver detection system, introduced in Scientific progresscould be used to improve the sensing capabilities of robotic, haptic and prosthetic systems.

“During a conversation, my 9-year-old daughter, Oriana Wei, told me about a documentary she had watched in the UK about the platypus,” Di Wei, lead author of the paper, told Tech Xplore. “She asked me, ‘Did you know that the platypus is an egg-laying mammal that doesn’t use its eyes to hunt?’”

“His question sparked my curiosity about the platypus’ sensory capabilities. That curiosity led me to a deeper exploration of the platypus’ remarkable sensory system, which ultimately inspired this research.”

The platypus has a unique dual sensory system that sets it apart from many other aquatic and egg-laying animals. This sophisticated sensory system allows it to detect electrical and mechanical changes in its environment, enhancing its ability to spot prey or potential threats without relying on sight.

“We sought to replicate the platypus’ capabilities in an artificial skin that combines both tactile and teleperceptive features,” Wei said. “Our main goal was to extend the perceptual range of artificial systems, allowing robots to sense and interact with their environment without relying solely on physical contact.”

“This could significantly improve interaction and control in robotic applications, overcoming the limitations of traditional tactile sensors that rely on direct contact to operate effectively.”

The platypus-inspired skin design developed by Wei and his colleagues relies on two key principles: contact electrification and electrostatic induction. When skin comes into contact with another material, the overlapping electron clouds in the two materials facilitate the transfer of electrons, generating triboelectric electricity. This allows the skin to perceive tactile stimuli.

To gather sensory information at a distance (i.e. teleperception), the skin instead relies on electrostatic induction. Essentially, the structured doping of nanoparticles in the elastomer on which the skin rests enhances the dielectric polarization, allowing the system to detect changes in electric fields when charged objects are nearby.

“In terms of composition, the multi-receptor skin follows a single-electrode design,” Wei explains. “It comprises a PTFE and PDMS thin film, a structured doped elastomer integrated with inorganic nonmetallic nanoparticles to enhance dielectric properties, a silver nanowire (AgNW) layer functioning as an electrode, and a PDMS-encapsulated substrate providing flexibility and protection.”

The main advantage of the sensing system developed by Wei and his colleagues is its dual-sensor design, which mimics the electroreception and mechanoreception capabilities of platypuses. This unique design allows the skin to accurately detect objects and collect tactile information with high sensitivity, both to touch and at a distance.

“Unlike traditional non-contact or pre-contact sensors that typically rely on detecting changes in proximity or basic capacitance, our multi-receptor skin offers a fundamentally different approach through enhanced polarization mechanisms,” Wei said.

“Traditional systems often suffer from sensitivity and accuracy limitations due to weaker charge interactions or surface-level charge sensing. Ours improves charge capture by exploiting a structured doped elastomer, which amplifies local electric fields and enhances dielectric polarization.”

Combined with deep learning techniques, the team’s platypus-inspired skin achieved very promising results, enabling rapid material identification with 99.56% accuracy, as well as the detection of distant objects.

Compared to conventional sensing systems, which often struggle to regulate charge and detect objects in varied environments, the multi-receptor skin was shown to better control its charge while maintaining stability in dynamic real-world environments.

“We have comprehensively reproduced the electroreception mechanism of the platypus,” Wei said. “Specifically, we found that the structured doping of nanoparticles in the elastomer matches the highly ordered arrangement of the platypus’ electroreceptors on its beak. This unique design greatly improves the sensitivity, enabling precise charge capture.”

“Furthermore, we found that the high electronegativity of the multi-receptor skin reflects the platypus’ single-polarity receptors, enabling dynamic charge control similar to its natural system.”

The skin designed by this team of researchers could contribute to the development of new technologies capable of detecting objects at a distance, also called teleperception systems. These systems could have a wide range of practical applications, from environmental monitoring in extreme climates to human-machine interaction and autonomous robot navigation.

“In practical terms, this bio-inspired replica of the platypus’ dual sensory system, combining both tactile and teleperception, is a major breakthrough in multimodal sensing,” Wei said. “This breakthrough addresses the limitations of traditional non-contact sensors, enabling more accurate and reliable performance in harsh environments.”

Wei and his colleagues’ recent work could pave the way for the development of other detection systems based on dual-sensor designs. In parallel, the researchers are working to further improve their multi-receiver system by increasing its versatility and facilitating its large-scale deployment.

“Our future research will focus on improving the capabilities of the electronic receiver, not only through further integration of artificial intelligence, but also by advancing hardware innovations to extend the range and accuracy of electric field detection,” Wei said.

“Concretely, we want to improve the adaptability and robustness of the system in extreme or unpredictable environments. In addition, we will refine the electronic receiver by incorporating additional sensory modalities, allowing it to respond to more complex stimuli and offer a wider range of perception.”

In their upcoming studies, Wei and his colleagues will also try to optimize the data processing capabilities of their system, so that it can reliably process data and accurately detect objects in real time. This could be particularly beneficial for applications that require rapid processing of sensory data, such as autonomous vehicles and human-machine interfaces.

“By pushing the boundaries of teleperception and sensory technology, we also hope to expand the applicability of our skin to advanced robotics, medical devices and beyond,” Wei added.

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