An e-skin simultaneously mimicking SA- and RA- mechanoreceptors can analyze objects based on their physical properties, such as the surface texture, sense of shape, pressure, and dynamic or static strain 10. Subsequently, the tactile sensation has been extensively explored by several researchers, and different strategies have been employed to mimic each type of mechanoreceptor. demonstrated the first prosthetic hand in 1974 9. Based on physical feedback principles, Clippinger et al.
#PIEZO SENSOR SKIN#
The interest in the sensory system of the human skin began in the late 1970s when Knibestöl and Vallbo analyzed 61 mechanoreceptor units in the glabrous skin 8. Similarly, Ruffini endings and Pacinian corpuscles are representative of SA-II and RA-II however, they have large receptive fields and respond to large pressures and high vibration frequencies.īased on human tactile perception principles, artificial tactile perception systems can be advanced similarly to perceive complex mechanical stimuli, enabling robots or artificial prosthetics to interact with the surrounding environment efficiently. Merkel receptors and Meissner corpuscles are representative of SA-I and RA-I they have small receptive fields and respond to minor pressures and low vibration frequencies. With regards to the positioning of these mechanoreceptors in the glabrous skin, Merkel receptors and Meissner corpuscles are located close to the surface of the skin, whereas Ruffini endings and Pacinian corpuscles are located deeper in the skin. The number and densities of these mechanoreceptors vary within the separate subregions of the glabrous skin and exhibit different resolutions. In the glabrous skin of one hand, there are ~17,000 cutaneous mechanoreceptors 5, which are categorized into four major types: Meissner’s corpuscles, Pacinian corpuscles, Merkel cells, and Ruffini endings (Fig. Generally, mechanoreceptors are spread over the entire area of the human skin. They differ with regard to the sizes and structures of their receptive fields and exhibit different sensitivities to static and dynamic stimuli 5, 6. SA-mechanoreceptors respond to static stimuli by showing continuous response to the maintained skin deformation, whereas RA-mechanoreceptors respond to dynamic stimuli by showing on and off responses with respect to the changes in skin deformation 4. Subsequently, the brain examines the type of the external stimulus using rapidly adaptive (RA) and slowly adaptive (SA) mechanoreceptors. When an external stimulus is applied, the sensory organs of the skin generate a receptive potential that is transmitted to the brain through axons 2, 3.
In the human body, the skin is the largest biological sensory system containing complex arrays of mechanoreceptors. The advancement of AI systems has facilitated the scale-up of e-skins that can emulate biological sensory systems and introduce a sense of touch for humanoid robots and those who wear prosthetic devices. The development of a self-powered electronic skin (e-skin) inspired by human mechanoreceptors is a prime need to restore sensory functions. Researchers globally have developed artificial organs such as bionic eyes 1 that can provide sensory capabilities to robots or restore sensory feelings to the disabled. Over the last few decades, artificial intelligence (AI) systems have been replicating biological functions realistically. The response and reset times showed by SA-mechanoreceptors were 11 and 18 ms under 1-Hz frequency, which are rapid enough for practical e-skin applications. Mechanoreceptors further detected several stimuli of various pressures with low and high frequencies. Based on piezoelectric sensing principles, the proposed e-skin can simultaneously mimic static and dynamic pressure signals.
The SA- and RA-mechanoreceptors demonstrated distinguished features such as grasping of objects and detection of their surface textures. We proposed SA- and RA-mechanoreceptors based on n-type and semi-insulating GaN nanowire arrays. However, the complex process of merging multimode sensors to mimic SA- and RA-mechanoreceptors hinders their utilization in e-skins. Based on human tactile perception principles, the fabrication of a self-powered electronic skin (e-skin) that simultaneously mimics SA- and RA-mechanoreceptors is a prime need for robots and artificial prosthetics to interact with the surrounding environment. Human skin contains slowly adaptive (SA) and rapidly adaptive (RA) mechanoreceptors, which respond differently to external stimuli.
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