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Page 2 of 26 Jin et al. Soft Sci 2023;3:8 https://dx.doi.org/10.20517/ss.2022.34

Keywords: Intelligent robotic, tactile sensing, object recognition, human-machine interaction, tactile sensor,
electronic skin

INTRODUCTION
Haptic perception is one of the essential sensations for human beings to collect ambient information ; it
[1]
can distinguish multiple sensory stimuli through mechanoreceptors and thermoreceptors, and helps
humans to improve grasping stability, recognize object properties and interact with the surrounding
[2]
environment . Haptic sensing has also been applied in robotics. Traditional robotic sensing using vision or
audio devices can detect environment information, while it is difficult to extract detailed features of target
[3]
objects through contactless measurement . Robotics with the capacity of tactile sensing can accurately
detect external force, vibration, temperature, and other contact stimuli . Therefore, tactile sensing
[4]
technologies have been widely utilized in intelligent robotics for stable grasping , dexterous
[5]
[7]
[6]
manipulation , object properties recognition , and human-machine interaction .
[8]
Tactile sensor is the key device to convey contact stimuli into processable signals based on different sensing
mechanisms, such as piezoresistive, capacitive, piezoelectric, triboelectric, magnetic, and optical sensing .
[9]
To imitate the somatosensory of human beings, robotics may require numerous sensors integrated with
their bodies, and it is desirable for tactile sensors to simultaneously measure multi-modal signals. Thus,
several types of promising tactile sensors, such as tri-axis force sensors , large-scale flexible sensing
[10]
arrays , and multi-modal sensors , have been widely used in robotics for tactile perception. To satisfy the
[12]
[11]
requirement of intelligent robotics, researchers have been pursuing high-performance tactile sensors by
studying highly sensitive materials and novel structural designs [14,15] . Development of flexible tactile
[13]
sensors with high sensitivity, wide detection range, fast dynamic response, and desirable repeatability
remains the fundamental requirement for robotic tactile perception.

With the usage of tactile sensors and advanced interactive technology, robotics can work in unpredictable
and changeable spaces rather than structured environments such as production lines . It is of great
[16]
significance for robotics with tactile perception to perform complicated tasks and interact with external
objects, especially human beings. Before conducting specific tasks, robotics are required to explore the
[17]
object’s properties, such as shape, material, texture, etc. . When extracting surface properties, tactile
sensors show significant advantages over traditional vision and audio devices, and they can also measure the
object global or even internal properties. Besides, in robotic grasping and dexterous operation tasks,
grasping stability need to be carefully considered. Actually, robotics is more desired to perform interactive
tasks with human beings. Based on interaction level, human-machine interactions (HMIs) can be classified
[18]
[19]
into human beings’ parameters measuring , input interface for robotic controlling , and close-looped
duplex interaction with sufficient feedback .
[8]
This study provides an overview of the latest progress of tactile sensing technologies and their applications
in intelligent robotics, as shown in Figure 1. Section “REQUIREMENTS OF TACTILE SENSING IN
ROBOTICS” summarizes the significance and requirements of tactile sensors in robotic applications.
Section “PROGRESS OF FLEXIBLE TACTILE SENSORS FOR ROBOTICS” discusses the working principle
as well as the characteristics of several promising tactile sensors. Then, Section “APPLIED TACTILE
SENSORS IN ROBOTIC APPLICATIONS” discussed tactile sensing technologies, especially data
processing methods and their applications. Finally, Section “SUMMARY AND FUTURE PROSPECTS”
summarized the challenges and prospects of robotic tactile sensing technologies.