detection; furthermore, mechanisms or devices to detect other stimuli, such as strain, temperature, and humidity, may be integrated. A tactile feedback system, integrated with a prosthetic hand, was demonstrated in 1974, [2] and since then, a variety of tactile sensors have been actively developed for use in various applications, such as touch screens and robotic hands.
Flexible tactile sensors capable of measuring mechanical stimuli via physical contact have attracted significant attention in the field of human-interactive systems. The utilization of tactile information can complement vision and/or sound interaction and provide new functionalities. Recent advancements in micro/nanotechnology, material science, and information technology have resulted in the development of high-performance tactile sensors that reach and even surpass the tactile sensing ability of human skin. Here, important advances in flexible tactile sensors over recent years are summarized, from sensor designs to system-level applications. This review focuses on the representative strategies based on design and material configurations for improving key performance parameters including sensitivity, detection range/linearity, response time/hysteresis, spatial resolution/crosstalk, multidirectional force detection, and insensitivity to other stimuli. System-level integration for practical applications beyond conceptual prototypes and promising applications, such as artificial electronic skin for robotics and prosthetics, wearable controllers for electronics, and bidirectional communication tools, are also discussed. Finally, perspectives on issues regarding further advances are provided.
Tactile
sensor arrays have attracted considerable attention for
their use in diverse applications, such as advanced robotics and interactive
human–machine interfaces. However, conventional tactile sensor
arrays suffer from electrical crosstalk caused by current leakages
between the tactile cells. The approaches that have been proposed
thus far to overcome this issue require complex rectifier circuits
or a serial fabrication process. This article reports a flexible tactile
sensor array fabricated through a batch process using a mesh. A carbon
nanotube–polydimethylsiloxane composite is used to form an
array of sensing cells in the mesh through a simple “dip-coating”
process and is cured into a concave shape. The contact area between
the electrode and the composite changes significantly under pressure,
resulting in an excellent sensitivity (5.61 kPa–1) over a wide range of pressure up to 600 kPa. The mesh separates
the composite into the arranged sensing cells to prevent the electrical
connection between adjacent cells and simultaneously connects each
cell mechanically. Additionally, the sensor shows superior durability
compared with previously reported tactile sensors because the mesh
acts as a support beam. Furthermore, the tactile sensor array is successfully
utilized as a Braille reader via information processing based on machine
learning.
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