4D Printing Strain Self‐Sensing and Temperature Self‐Sensing Integrated Sensor–Actuator with Bioinspired Gradient Gaps

Abstract

Integrated sensor–actuators with exciting functionalities, such as action self‐sensing, position self‐sensing, posture self‐sensing, or active sensing, are promising for applications in biomedical device, human–machine interaction, intelligent self‐protection devices, and humanoid robots. Despite recent progress, it remains challenging to achieve a macroscopical integrated sensor–actuator in a material system with microstructures. To address this critical challenge, a 4D printing bioinspired microstructure strategy is reported to design a high‐performance integrated sensor–actuator capable of simultaneous actuation and sensation. Decoupled thermal stimulation and strain sensation is achieved by combining nanocarbon black/polylactic acid composites with bioinspired gradient microgap structures. As a result, printed integrated sensor–actuators can actively touch objects triggered by thermal stimulation and self‐sense the touching state through the resistance change. It is anticipated that the basic design principle underlying this behavior can be used to develop integrated sensor–actuators of various shapes and functionalities to meet desirable applications.

4D Printing: A Review on Recent Progresses

“…However, the whole time of completely deformation under the stimulus is nearly 20 min. Chen et al designed a high-performance integrated sensor–actuator with strain-sensing and temperature self-sensing and the average materials response time is about 20 s [ 185 ]. On the other hand, most existing materials make the response to only one stimulus and it will not work in the case of stimulus producing equipment failure.…”

Fused Filament Fabrication of Polymers and Continuous Fiber-Reinforced Polymer Composites: Advances in Structure Optimization and Health Monitoring

“…An important technology developed for health monitoring is the so-called self-sensing technology, for which the 3D printed material is used to sense its structural state, acting as a strain sensor [ 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ]. The 3D printing materials enabling such a self-sensing ability of the material is part of 4D printing technology [ 91 ]. The structure monitoring is based on measuring the electrical resistance of the materials, for which a certain level of electrical conductivity is ensured by conductive agents such as carbon black, graphene, carbon nanotubes, carbon continuous fiber, or copper wire leading to conducting paths.…”

“…The advantage of this system is that it provides a 2D strain field of the material that appears suitable to obtain local information, and hence, more precise sensing and detection of potential damage. As suggested in [ 91 ], the application range of this technology includes intelligent devices (biomedical instruments, human-machine interaction systems, protection devices, robots, etc. ), but also conventional applications such as a bikes (Limburg Bike project, Brightlands Materials Center (the Netherlands), [ 93 ]) and helmets ([ 89 ], with the use of another 3D printing technology—photocuring 3D printing) with the detection of damage to improve safety.…”

“… Self-sensing technology to detect strain and temperature variation in 3D printed PLA/carbon black composite: ( a ) material design showing gaps, ( b ) resistance variation when the composite is subjected to compression, and ( c ) resistance variation when the composite is subjected to a temperature increase from 30 °C to 52.6 °C [ 91 ] (copyright (2020), with permission from Wiley-VCH Verlag GmbH & Co). …”

Four-Dimensional Printing of Alternate-Actuated Composite Structures for Reversible Deformation under Continuous Reciprocation Loading

“…However, this internal force is generally small, so that 4D printed structures are not expected to be stiff during deformation. This explains why current 4D printed structures with significant deformation usually have low stiffness during actuation: it is caused by a decrease in the modulus of the smart material due to an externally induced deformation (Shiblee et al, 2018;Chen et al, 2020) or by a reduced stiffness of the deformation area due to a hinge structure (Zhu et al, 2018). The end result is that the structure is unable to carry loads at certain points in the deformation process.…”