Researchers design platypus-inspired bionic multi-receptor skin

While engineers have developed increasingly advanced bio-inspired systems over the past decades, the sensing capabilities of these systems are typically far less advanced than those observed in humans and other animals.

The design and fabrication of more sophisticated sensors and artificial skins could further improve these systems, allowing them to accurately pick up a broad range of sensory information from their surroundings.

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

The team’s multi-receptor sensing system, introduced in Science Advances, could be used to boost the sensing capabilities of robotic, haptic and prosthetic systems.

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

“Her question sparked my curiosity about the sensory abilities of the platypus. This curiosity led to a deeper exploration of the platypus’s remarkable sensory system, which ultimately inspired this research.”

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

“We aimed to replicate the platypus’ capabilities in an artificial skin that combines both tactile and tele-perception functionalities,” said Wei. “Our primary goal was to extend the perceptual range of artificial systems, allowing robots to detect and interact with their environment without relying solely on physical contact.

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

The platypus-inspired skin design developed by Wei and his colleagues is based on two key principles, namely contact electrification and electrostatic induction. When it touches another material, the overlap of electron clouds in the two materials facilitates the transfer of electrons, ultimately generating triboelectric electricity. This allows the skin to perceive tactile stimuli.

To gather sensory information from afar (i.e., tele-perception), the skin instead relies on electrostatic induction. Essentially, the structured doping of nanoparticles in the elastomer that the skin is based on enhances 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,” explained Wei. “It comprises a PTFE and PDMS thin film, a structured-doped elastomer embedded with inorganic nonmetal nanoparticles to boost dielectric properties, a silver nanowire (AgNW) layer functioning as the electrode, and a PDMS encapsulated substrate providing flexibility and protection.”

The primary advantage of the sensing system developed by Wei and his colleagues is its dual sensory design, which mimics the electroreception and mechanoreception capabilities of platypuses. This unique design allows the skin to accurately detect objects and gather tactile information with a high sensitivity, both when touching them and from afar.

“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,” said Wei.

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

When combined with deep learning techniques, the team’s platypus-inspired skin attained highly promising results, enabling the rapid identification of materials with a 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 varying environments, the multi-receptor skin was found to better control its charge while also retaining its stability in dynamic real-world settings.

“We comprehensively replicated the platypus’ electroreception mechanism,” said Wei. “Specifically, we found that the structured doping of nanoparticles in the elastomer corresponds to the platypus’ highly ordered electroreceptor arrangement on its bill. This unique design significantly enhances sensitivity, allowing for precise charge capture.

“Additionally, we uncovered that the strong electronegativity of the multi-receptor skin mirrors the platypus’ single-polarity receptors, achieving dynamic charge control akin to its natural system.”

The skin designed by this team of researchers could contribute to the development of new technologies that can sense objects from afar, also known as tele-perception systems. These systems could have a wide range of real-world applications, ranging from environmental monitoring in extreme climates to human-machine interaction and autonomous robot navigation.

“In practical terms, this bio-inspired replication of the platypus’ dual sensory system—combining both tactile and tele-perception—marks a major advancement in multi-modal sensing,” said Wei. “This breakthrough addresses the limitations of traditional non-contact sensors, enabling more accurate and reliable performance in challenging environments.”

The recent work by Wei and his colleagues could pave the way for the development of other sensing systems that rely on dual sensory designs. Meanwhile, the researchers are working on further improving their multi-receptor system by enhancing its versatility and facilitating its large-scale deployment.

“Our future research will focus on enhancing the electronic receptor’s capabilities not only through deeper integration of artificial intelligence but also by advancing material innovations to extend electric field sensing range and precision,” said Wei.

“Specifically, we aim to improve the system’s adaptability and robustness in extreme or unpredictable environments. Additionally, we will refine the electronic receptor by incorporating additional sensory modalities, enabling it to respond to more complex stimuli and offer a broader range of perception.”

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

“By pushing the boundaries of tele-perception and sensory technology, we also hope to expand our skin’s applicability in advanced robotics, medical devices, and beyond,” added Wei.

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