Beyond Human Touch Perception: An Adaptive Robotic Skin Based on Gallium Microgranules for Pressure Sensory Augmentation

Abstract

Robotic skin with human‐skin‐like sensing ability holds immense potential in various fields such as robotics, prosthetics, healthcare, and industries. To catch up with human skin, numerous studies are underway on pressure sensors integrated on robotic skin to improve the sensitivity and detection range. However, due to the trade‐off between them, existing pressure sensors have achieved only a single aspect, either high sensitivity or wide bandwidth. Here, an adaptive robotic skin is proposed that has both high sensitivity and broad bandwidth with an augmented pressure sensing ability beyond the human skin. A key for the adaptive robotic skin is a tunable pressure sensor built with uniform gallium microgranules embedded in an elastomer, which provides large tuning of the sensitivity and the bandwidth, excellent sensor‐to‐sensor uniformity, and high reliability. Through the mode conversion based on the solid–liquid phase transition of gallium microgranules, the sensor provides 97% higher sensitivity (16.97 kPa−1) in the soft mode and 262.5% wider bandwidth (≈1.45 MPa) in the rigid mode compared to the human skin. Successful demonstration of the adaptive robotic skin verifies its capabilities in sensing a wide spectrum of pressures ranging from subtle blood pulsation to body weight, suggesting broad use for various applications.

Liquid Metal-Based Electronics for On-Skin Healthcare

“…An all-soft capacitive sensor with tunable sensitivity was demonstrated for the gesture quantification of the proximal interphalangeal. In addition, the solid-liquid phase transition of the gallium microgranule-based dielectric layer could facilitate a wide range and high sensitivity of the sensors (Figure 11C) [35]. This temperature-dependent rigid-soft mode conversion provides a 97% lower minimum and 262% higher detectable pressure, compared with the detection range of human skin.…”

“…As a result, pressure, strain, pain sensors, and other functional circuits for temperature and perspiration monitoring to serve as artificial skin have been designed [32][33][34]. In addition, blood pressure and blood pulsation in subcutaneous tissue could also be identified with a pressure sensor to monitor subtle physiological changes [35]. Prior to the applications of LMs, the representative properties of LMs will be thoroughly discussed in terms of their physical properties (conductivity, surface tension, thermal conductivity, etc.…”

Deep-Learning Enabled Active Biomimetic Multifunctional Hydrogel Electronic Skin

“…Human skin is extremely crucial for its protective, immunological, and tactile functions. Inspired by the natural human skin, scientists have developed various types of electronic skins (e-skins). , The tactile sensing capability is critical for these electronic skins; for example, it allows intelligent robots to interact effectively with their environment. , A variety of pressure sensing techniques have been developed for e-skins based on various mechanisms such as piezoresistive, , capacitive, , piezoelectric, , and triboelectric ones. , In addition to pressure sensing, identification/recognition of different types of material or texture/roughness is also essential for the e-skin, especially when the robots are required to have real intelligence to interact with their surroundings. − However, so far, a comprehensive e-skin, which can simultaneously detect the pressure, material/substance, and texture/roughness, has rarely been reported.…”

“…1,2 The tactile sensing capability is critical for these electronic skins; for example, it allows intelligent robots to interact effectively with their environment. 3,4 A variety of pressure sensing techniques have been developed for e-skins based on various mechanisms such as piezoresistive, 5,6 capacitive, 7,8 piezoelectric, 9,10 and triboelectric ones. 11,12 In addition to pressure sensing, identification/recognition of different types of material or texture/roughness is also essential for the e-skin, especially when the robots are required to have real intelligence to interact with their surroundings.…”

Stretchable, Adhesive, and Bioinspired Visual Electronic Skin with Strain/Temperature/Pressure Multimodal Non-Interference Sensing

“…Human skin, containing lots of receptors for sensing and distinguishing multiple stimuli, is one of the most important somatosensory systems. , Artificial multifunctional electronic skin (e-skin) that can mimic and even surpass the human skin sensory functions is anticipated to play an important role in personal healthcare, − prosthetics, − soft robotics, − human–machine interaction, − and other fields. − However, cross-talks prevent accurate measurements of the target input signals when parts of them are simultaneously present . In general, several combination effects of the materials (e.g., thermoelectric, piezoresistive, triboelectric, capacitive, and ferroelectric) and structural engineering (e.g., hierarchical patterns, nanohelixes, micropyramids, microridges, and interlocked microstructures) yielding different signals are the most straightforward method to design multimodal sensors with decoupled sensing mechanisms.…”