Bioinspired strategies for biomimetic actuators from ultrafast to ultraslow

Motile plant tissues can control their configurations and regulate their motion speed according to their specific requirements,which offer various protypes for biomimetic actuators with controlled motion speed.In this perspective,we focus on the speed control of plant tissues and the bioinspired strategies for speed regulation of artificial actuators.We begin with a summary to the strategies and mechanisms of motile plant tissues for controlling motion speed,ranging from ultrafast to ultraslow.We then exemplify the models for fabricating bioinspired artificial actuators and briefly discuss current application scenarios of actuators with varying speeds from ultrafast to ultraslow.Finally,we propose potential strategies for the speed regulation of actuators.

Behavior Analysis of Biomimetic Soft Bending Actuators in Free Motion and Contact

Bioinspired Soft Bending Actuators (SBA) are increasingly being used in rehabilitation, assistant robots, and grippers. Despite many investigations on free motion modeling, understanding how these actuators interact with the environment requires more detailed research. It is caused by high compliance and nonlinearity of bioinspired soft material, which leads to serious challenges in contact conditions. In this paper, a continuous deformation analysis is presented to describe the free motion nonlinear behavior of the actuator. Based on the achieved result, this study proposes static modeling of SBA affected by a concentrated external force. For this purpose, the finite rigid element method is utilized, which is based on discretizing the actuator into smaller parts and assuming these parts as rigid serial links connected by nonlinear torsional springs. To verify the proposed model, two kinds of forces are considered to be acting on the actuator, i.e. following force and constant direction force. In addition, the effect of gravity on the actuator configuration is also investigated. The validity of the model has been demonstrated through experiments in free motion, contact conditions and the presence of gravity. It generally shows that the prediction error of robot configuration is lower than 7.5%.

Correlation of Direct Piezoelectric Effect on EAPap under Ambient Factors

Direct piezoelectricity of electro-active papers （EAPap） is analysed in this paper. The test setups for direct effect are designed and determined. Different ambient factors impacting the piezoelectricity of EAPap, such as temperature, humidity, and strain rate, are applied and analyzed. Strong piezoelectricity of EAPap is found on the basis of the test results and in comparison with polyvinylidene fluoride （PVDF） and lead zirconate titanate （PZT）-5H. The maximum piezoelectric constant is achieved to be 504 pC/N. The reason of strong piezoelectricity of EAPap is discussed in this paper. The potential of EAPap as a biomimetic actuator and sensor is also investigated.

A multistimuli-responsive fluorescent hydrogel based on a fluorescence response to macromolecular segmental motion

Fluorescent hydrogels with fast and reversible responses have attracted extensive attention, and it remains a challenge to designmultistimuli-responsive fluorescent hydrogel through a facile and versatile method. Meanwhile, the segmental motion inhydrogels is of significance for the various functions of hydrogels such as chemical reactivity, self-healing, and mechanicalstrength, etc., however, it is difficult and complicated to in situ investigate the segmental motion under different conditions. In thiswork, a multistimuli-responsive fluorescent hydrogel was designed and fabricated by introducing a tetraphenylethylene (TPE)derivative as a nonaggregated crosslinker in the gel network. Since the intermolecular rotation of TPE at the crosslinking pointwas directly integrated with the dynamic conformational transition of the macromolecular network, the mobility of macromolecularsegments can be monitored by the fluorescence intensity of the hydrogel. The prepared hydrogel has promising fluorescenceresponses to temperature, pH, metal ions, and hydrogen bonding agents, and characterization of the fluorescence and the chainsegmental motion showed that the weaker the mobility of the network macromolecular chain is, the stronger the fluorescenceintensity is. Furthermore, due to the multistimuli-responsive fluorescence of the hydrogel, such fluorescent hydrogels can bedesigned as reversible patterning displays and biomimetic color/shape adjustable actuators, with various potential applications.