Flexible Plasmonic Optical Tactile Sensor for Health Monitoring and Artificial Haptic Perception

Abstract

specialized to respond to various physical stimuli (e.g., temperature, pressure, and stretching), humans can rapidly and accurately locate and identify objects via haptic perception. [5][6][7] To emulate human skin with haptic pressure sensation, tactile sensors capable of measuring contact pressure/force have been extensively exploited with diverse nanomaterials and nanostructures over the past decade. [8][9][10][11][12][13] For example, Gong et al. proposed a flexible and highly sensitive pressure sensor by sandwiching ultrathin gold nanowire between elastomer sheets that allowed real-time monitoring of arterial blood pressure through skin surface contact. [10] Cao et al. demonstrated enhanced tactile sensitivity for surface texture discerning based on an optimized micropyramid structure assembled with a single-walled carbon nanotube. [13] The general principle of such sensors is to transduce the mechanical stimuli into electrical signals through the effects of piezoelectricity, capacitance, or piezoresistance. [14,15] Tactile sensors made of piezoelectric elements have shown advantages such as high sensitivity, low power consumption, and high response frequency, which make them, especially promising for dynamic pressure measurements such as slip and vibration detection in robotics. [15][16][17] However, the piezoelectric effects are generally temperature-dependent, and not suitable for static pressure measurement due to charge leakage. [18,19] Capacitive sensors can monitor both static and dynamic pressure with the merits of temperature independence and long-term stability but suffer from parasitic effects, complex circuits, and limited working range. [20][21][22] By comparison, piezoresistive sensors have been more predominantly used for tactile sensing due to their simple structure, easy readout, and broad sensing range. [23,24] However, they typically exhibit undesirable hysteresis and signal drift, inducing practical difficulties in high-precision measurements. [18] Besides, other issues such as electromagnetic interference (EMI) susceptibility, electrical safety, and biocompatibility of the electronic components in medical settings, are also common concerns of all aforementioned approaches that impair their widespread applications. [25,26] Recently, there have also been efforts in developing tactile sensors by using ion conductors and ionic luminophores that can convert mechanical stimuli into luminescence. [27,28] These sensors provide visual-tactile feedback with spatially-resolved capability, but suffer from long response

Packaged Elastomeric Optical Fiber Sensors for Healthcare Monitoring and Human‐Machine Interaction

“…Flexible optical sensors have been found enormous utility in healthcare, [1][2][3][4] human-machine interaction (HMI), [5][6][7][8][9] and robotics, [10][11][12][13] due to their high sensitivity, fast response, and anti-electromagnetic interference. To date, silica optical fiber, [14,15] micro/nano fiber, [16][17][18][19] elastomeric polymer optical fiber, [20][21][22] and protein waveguide [23] have been widely used to construct flexible optical sensors. A prominent example is fiber Bragg gratings (FBGs) enabled large-area tactile-sensitive skin that can detect contact location and force by analyzing the shift of the resonant wavelength of each FBG.…”

Soft Optical Waveguides for Biomedical Applications, Wearable Devices, and Soft Robotics: A Review

“…Elastomers, which are natural or synthetic polymers with elastic properties, can deform elastically under tensile and compressive stresses, and then return to their original shape. [44,45] These materials are highly flexible and transparent, making them suitable for use not only as complete optical waveguides, but also as cladding or encapsulation for soft optical wearable devices.…”

Soft Biomimetic Fiber-Optic Tactile Sensors Capable of Discriminating Temperature and Pressure

“…Biomimetic tactile sensors that can emulate the sensory ability of human skin are of paramount importance for applications in skin prosthetics, assistive robotics, and health monitoring. − The human skin is a complex integrated sensory network composed of diverse sensory receptors, which enable humans to precisely perceive and discriminate various thermal and mechanical stimuli. − In the past decade, numerous efforts have been dedicated to developing skin-like tactile sensors with capabilities of perceiving thermal and mechanical stimuli, such as temperature, pressure, strain, and vibration. − Liao et al demonstrated a multifunctional tactile sensor composed of ZnO nanowires and polyurethane fibers that possessed strain, temperature, and UV-sensing capabilities . Hou et al proposed a skin-like multifunctional sensor based on elastic films of graphene that allowed sensitive detection of temperature and pressure .…”