High‑Performance Fasciated Yarn Artificial Muscles Prepared by Hierarchical Structuring and Sheath-Core Coupling for Versatile Textile Actuators

High-performance yarn artificial muscles are highly desirable as miniature actuators,sensors,energy harvesters,and soft robotics.However,achieving a yarn artificial muscle that covers all the properties of excellent actuation performance,mechanical robustness,structural stability,and high scalability by a low-cost strategy is still a great challenge.Herein,a bio-inspired fasciated yarn structure is first reported for creating robust high-performance yarn artificial muscles.Unlike conventional strategies that leverage costly materials or complex processing,the developed yarn artificial muscles are constructed by hierarchically helical and sheath-core assembly design of cost-effective common fibers,such as viscose and polyester.The hierarchically helical sheath structure pushes the theoretical limit of the inserted twist in yarns and endows the yarn muscles with large stroke(5815°cm^(-1))and high work capacity(23.5 J kg^(-1)).Due to the rapid water transfer and efficient energy conversion of inter-sheath-core coupling,the as-prepared yarn muscles possess fast response,high rotation accelerated speed,and low recovery hysteresis.Moreover,the inactive core yarn serves as support for internal tethering and load-bearing,enabling these yarn muscles to maintain a self-stable structure,robust life cycle and mechanics.We show that the yarn muscle fabricated in this method is readily available and highly scalable for achieving high-dimensional actuation deformations,which considerably broadens the application scenarios of artificial muscles.

A Survey on Pneumatic Muscle Actuators Modeling

The aim of this article is to provide a survey on the most popular modeling approaches for PMAs （pneumatic muscle actuators）. PMAs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last decade, there has been an increase in the industrial and scientific utilization of PMAs, due to their advantages such as high strength and small weight, while various types of PMAs with different technical characteristics have appeared in the literature. This article will： （a） analyse the PMA＇s operation from a mathematical modeling perspective; （b） present their merits and drawbacks of the most common PMAs; and （c） establish the fundamental basis for developing industrial applications and conducting research in this field.

Ultralong Stretchable Soft Actuator(US2A):Design,Modeling and Application

Actuator plays a significant role in soft robotics.This paper proposed an ultralong stretchable soft actuator(US2A)with a variable and sizeable maximum elongation.The US2A is composed of a silicone rubber tube and a bellows woven sleeve.The maximal extension can be conveniently regulated by just adjusting the wrinkles’initial angle of the bellows woven sleeve.The kinematics of US2A could be obtained by geometrically analyzing the structure of the bellows woven sleeve when the silicone rubber tube is inflated.Based on the principle of virtual work,the actuating models have been established:the pressure-elongation model and the pressure-force model.These models reflect the influence of the silicone tube’s shell thickness and material properties on the pneumatic muscle’s performance,which facilitates the optimal design of US2A for various working conditions.The experimental results showed that the maximum elongation of the US2A prototype is 257%,and the effective elongation could be variably regulated in the range of 0 and 257%.The proposed models were also verified by pressure-elongation and pressure-force experiments,with an average error of 5%and 2.5%,respectively.Finally,based on the US2A,we designed a pneumatic rehabilitation glove,soft arm robot,and rigid-soft coupling continuous robot,which further verified the feasibility of US2A as a soft driving component.

IPMC人工肌肉的特性及其应用

介绍了IPMC人工肌肉致动器的制备、致动特性和应用 。

IPMC的力输出特性

IPMC(ion-exchange polymer metal com-posite)离子交换聚合物-金属复合材料)是一种人工肌肉材料,其较低的驱动电压能产生较大的位移变形,研究了IPMC这种智能材料的输出力特性。实验选取了不同电压幅值,不同频率的方波、三角波、正弦波3种波形作为电激励信号,通过力传感器实测了IPMC试样末端的输出力。结果表明,随着电压幅值的增大,其输出力也增大;随着电刺激信号频率的降低,其输出力也增大;而波形对其输出力影响不显著。

人工肌肉IPMC电致动响应特性及其模型

采用自行设计的悬臂梁装置对人工肌肉IPMC的电致动响应特性进行测试,研究在直流电压作用下悬臂梁位移与电压的关系及在方波电压作用下位移与电压频率的关系,建立IPMC材料的力学模型;提出IPMC材料悬臂梁电致动挠曲线方程的大变形解法,导出作用于IPMC悬臂梁上的等效弯矩与电压、频率的函数。测试结果表明,在电压为5V时位移达到最大值11.1mm;当电压的频率大于30mHz时,随着频率的增加,悬臂梁的位移逐渐减小,且在30～100mHz时下降迅速。模型计算结果与测试结果最大相对误差在10%以内,证实了模型的准确性。

IPMC型柔顺手爪作动器的设计与性能测试

为克服传统手爪机构传动链多,耗能大,结构复杂等缺点,设计并制作了一种应用电致动智能材料(IPMC)的柔顺手爪。运用Pro/E软件设计IPMC手爪的主体结构,并分析其运动过程,最终装配完成IPMC手爪;运用激光位移传感器,精密电子秤和Canon相机测试了研制的4片IPMC驱动薄膜的末端位移,端部力和平均运动速度,并通过Labview测试系统对其进行采样和分析。实验结果表明:IPMC手爪驱动元件的角位移在3V电压激励下超过了180°(-3V电压下负向位移与+3V电压下正向位移之和);其末端位移大小为其自身(除固定部分外)总长;手爪驱动薄膜每片重量约为0.5mg,可抓握质量为1.6g左右的物体。该手爪结构简单、位移大、耗能低;同时,由于IPMC的柔顺特性,在抓取物体时它会贴附在其表面,而不破坏其表面精度。因此,这种手爪适用于抓取表面粗糙度要求高的物体。

一种离子交换树脂金属复合材料（IPMC）的力学参数测定

对一种新型的人工肌肉材料——离子交换树脂金属复合材料（IPMC）的力学性能参数进行了测试研究。进行了精密拉伸实验,测定了其弹性模量E和泊松比υ,确定了其本构关系,证实了其具有各向同性特性。测试研究为开展IPMC人工肌肉和其应用研究提供了参考数据。

Modeling and Design of H-Infinity Controller for Piezoelectric Actuator LIPCA

We proposed a dynamic model identification and design of an H-Infinity （i.e.H） controller using a LightweightPiezo-Composite Actuator （LIPCA）.A second-order dynamic model was obtained by using input and output data, and applyingan identification algorithm.The identified model coincides well with the real LIPCA.To reduce the resonating mode that istypical of piezoelectric actuators, a notch filter was used.A feedback controller using the Hcontrol scheme was designed basedon the identified dynamic model; thus, the LIPCA can be easily used as an actuator for biomemetic applications such as artificialmuscles or macro/micro positioning in bioengineering.The control algorithm was implemented using a microprocessor, analogfilters, and power amplifying drivers.Our simulation and experimental results demonstrate that the proposed control algorithmworks well in real environment, providing robust performance and stability with uncertain disturbances.

Soft actuator based on ion-exchange polymer-metal composite

Ion-exchange polymer-metal composite （IPMC） is a new electroactive material. It has large deformation and high force weight ratio in the presence of low voltage （〈1.5 V）. In this study a soft actuator known as artificial muscle based on IPMC was prepared. The IPMC actuator is composed of a perfluorinated ion-exchange membrane and platinum plated on both sides of the membrane by chemical means. Experiences and some key points are introduced in preparation of the IPMC. Electromechanical behaviors of the actuator are investigated, Factors related to the actuator performance are discussed.

Hardware Neural Networks Controlled MEMS Rotational Actuators and Application to Micro Robot

Hardware neural networks controlled rotational actuators and application to an insect type micro robot are reported in this paper. Millimeter size rotational actuators are fabricated by combining MEMS （Micro Electro Mechanical System） technology and shape memory alloy based artificial muscle wires. The actuator is composed of a pair of disk rotators and each rotor is suspended by four artificial muscle wires that are connected to the silicon frame. The rotational motion is generated by flowing the electrical current to each wire successively. Two actuators of different sizes are fabricated. The large actuator shows the displacement of 0.5 mm at the cycle time of 4 s. The small actuator shows 0.3 mm at 2 s. For controlling the actuator, the hardware neural networks are used. The hardware neural networks are composed of electrical circuits imitating cell bodies, excitatory synapses and inhibitory synapses. Four signal ports are extracted from four pairs of excitatory and inhibitory neurons and they are connected to the actuator. The small actuator is applied to the robot and built in the mid body of the robot. The shaft of the actuator is connected to the link mechanisms that transform the rotational motion to the locomotion. The appearance dimensions of the robot are 4.0, 2.7, 2.5 mm width, length and height. The robot performs forward and backward foot step like insects. The speed is 26.4 mm·min^-1 and the stepping width is 0.88 mm. Also, the robot changes the direction by external trigger pulses.

Dual-Ion Co-Regulation System Enabling High-Performance Electrochemical Artificial Yarn Muscles with Energy-Free Catch States

Artificial yarn muscles show great potential in applications requiring low-energy consumption while maintaining high performance. However, conventional designs have been limited by weak ion-yarn muscle interactions and inefficient “rocking-chair” ion migration. To address these limitations, we present an electrochemical artificial yarn muscle design driven by a dual-ion co-regulation system. By utilizing two reaction channels, this system shortens ion migration pathways, leading to faster and more efficient actuation. During the charging/discharging process, PF_6~- ions react with carbon nanotube yarn, while Li~+ ions react with an Al foil. The intercalation reaction between PF_6~- and collapsed carbon nanotubes allows the yarn muscle to achieve an energy-free high-tension catch state. The dual-ion coordinated yarn muscles exhibit superior contractile stroke, maximum contractile rate, and maximum power densities, exceeding those of “rocking-chair” type ion migration yarn muscles. The dual-ion co-regulation system enhances the ion migration rate during actuation, resulting in improved performance. Moreover, the yarn muscles can withstand high levels of isometric stress, displaying a stress of 61 times that of skeletal muscles and 8 times that of “rocking-chair” type yarn muscles at higher frequencies. This technology holds significant potential for various applications, including prosthetics and robotics.

Recent advances in flexible self-oscillating actuators

Soft actuators are constituted by a type of intelligent materials,and they can generate reversible mechanical motions under external stimuli.They usually achieve continuous actuation by manual turning on or off the power supply,which significantly increases the operation complexity.In contrast,self-oscillating actuators can achieve autonomous motions under constant stimuli,and have recently attained great advancements,as well as promoted the development of autonomous soft robotics.In this review,the latest achievements of soft oscillators are summarized.First,the self-oscillating mechanisms mainly including oscillating chemical reactions and self-shadowing-induced mechanical negative feedback loops are discussed.The oscillators constructed with various materials and configurations,driven by different stimuli and applied in different fields are then presented in detail.Finally,the difficulties and hopes of oscillators are presented.Overall,self-oscillating actuators are in the stage of vigorous development,and we believe that in the future,they will be used in various fields and make many scenarios more intelligent and autonomous.

Self-sensing actuators with programmable actuation performances for soft robots

Designing soft robots that are able to perceive unstructured,dynamic environments and their deformations has been a long-term goal.Previously reported self-sensing soft actuators were mostly constructed via integrating separate actuators and sensors.The actuation performances and the sensing reliability are affected owing to the unmatched materials and weak connections.Realizing a seamless integration of soft actuators and sensors remains a grand challenge.Here,we report a fabrication strategy to endow soft actuators with sensing capability and programmable actuation performances.The foam inside the actuator functions as actuator and sensor simultaneously,effectively addressing the conformability and connection reliability issues that existed in current self-sensing actuators.The actuators are lightweight(a decrease of 58%in weight),powerful(lifting a load of 433 times of its own weight),and versatile(coupling twisting and contraction motions).Furthermore,the actuators are able to detect multiple physical stimuli with high reliability,demonstrating their exteroception and proprioception capability.Two self-sensing soft robotic prototypes,including a bionic bicep and a bionic neck,are constructed to illustrate their multifunctionality.Our study opens up new possibilities for the design of soft actuators and has promising potential in a variety of applications,ranging from human-robot interaction,soft orthotics,to wearable robotics.

Sleeve Muscle Actuator： Concept and Prototype Demonstration

This paper presents the concept and prototype demonstration results of a new sleeve muscle actuator, which provides a significantly improved performance through a fundamental structural change to the traditional pneumatic muscle. Specifically, the sleeve muscle incorporates a cylindrical insert to the center of the pneumatic muscle, and thus eliminates the central portion of the internal volume. Through the analysis of the actuation mechanism, it is shown that the sleeve muscle is able to provide a consistent increase of force capacity over the entire range of motion. Furthermore, the sleeve muscle provides a significant energy saving effect, as a result of the reduced internal volume as well as the enhance force capacity. To demonstrate this new concept, a sleeve muscle prototype was designed and fabricated. Experiments conducted on the prototype verified the improvement in the force capacity and demonstrated a significant energy saving effect （20%-37%）. Finally, as the future work on this new concept, the paper presents a new robotic elbow design actuated with the proposed sleeve muscle. This unique design is expected to provide a highly compact and powerful actuation approach for robotic systems.

Re-engineering artificial muscle with microhydraulics

We introduce a new type of actuator,the microhydraulic stepping actuator(MSA),which borrows design and operational concepts from biological muscle and stepper motors.MSAs offer a unique combination of power,efficiency,and scalability not easily achievable on the microscale.The actuator works by integrating surface tension forces produced by electrowetting acting on scaled droplets along the length of a thin ribbon.Like muscle,MSAs have liquid and solid functional components and can displace a large fraction of their length.The 100μm pitch MSA presented here already has an output power density of over 200 W kg^(−1),rivaling the most powerful biological muscles,due to the scaling of surface tension forces,MSA’s power density grows quadratically as its dimensions are reduced.

A Hollow Polyethylene Fiber-Based Artificial Muscle

Recently,researches on artificial muscles for imitating the functions of the natural muscles has attracted wide attention.The fiber-shape actuators,shape-memory materials or deforming devices,which are similar to human muscle fiber bundles,have extensively studied and provided more possibilities for artificial muscles.Herein,we develop a thermal responsible fiber-shaped actuator based on the low-cost hollow polyethylene fiber.The sheath-core structured fibrous actuators and the stainless-steel conductive yarn winded pre-stretched polyethylene actuators are fabricated with the heating assisted pre-stretching procedure.The actuation mechanism of the thermal-responsive orientation change of molecular chains driving the actuation is discussed and demonstrated by 2D XRD patterns.These polyethylene-based fibrous actuators displayed three significant advantages including(i)color-turning and shape-changing bifunctional response,(ii)direct joule heating actuation and(iii)effective contraction(18%shrinkage of the pristine length)and lifting ability(the ratio of lifting weight to self-weight is up to 50).

表面粗化对IPMC人工肌肉性能的影响

离子聚合物金属复合材料(Ionic Polymer Metal Composite,IPMC)是由聚合物基底膜和金属电极复合而成的一种新型的离子型电致动材料.对基底膜进行表面粗化处理,改善聚合物基底和金属电极间交界面构筑方式是提高材料性能的重要方法.本文针对IPMC人工肌肉的制备提出了一种可控的基底膜定向表面粗化方法,基于UMT-2摩擦磨损试验机的线性往复运动设计了一套IPMC基底膜表面粗化装置.对比手工粗化,采用3种载荷对Nafion商业膜表面进行了机械粗化处理.对不同粗化条件获得的基底膜以相同的工艺制备IPMC,研究了不同粗化方法和条件对IPMC人工肌肉力和位移输出性能的影响.结果表明,机械粗化能够排除手工粗化过程中人为因素的影响,做到粗化加载的力度及方向性可控,使磨痕深浅均匀方向一致.相比手工粗化,通过机械粗化可以改善基底膜与电极层之间的构筑紧密程度,增加铂颗粒的吸附能力和沉积厚度,获得更为平整致密、裂隙均匀有序的表面电极,从而降低IPMC表面电阻,提升力和位移输出能力.致密且较厚的电极层同时可以阻挡一部分水分的泄露,延长IPMC有效工作的时间.该研究能够提升IPMC制备工艺的稳定性,为IPMC制备的标准化奠定基础,同时提高IPMC人工肌肉的驱动性能,对IPMC人工肌肉的进一步开发应用提供保障.

不锈钢丝/尼龙螺旋线圈型人工肌肉的制备及其性能研究

将廉价的尼龙线和不锈钢丝混纺制备螺旋线圈型人工肌肉,探索尼龙线直径和不锈钢丝股数对人工肌肉的电热致动性能影响。结果表明:随着尼龙线直径的增加,不锈钢丝/尼龙人工肌肉的一个工作循环时间增长,在相同刺激时间下输出力和收缩率大幅提升,且输出力与尼龙线直径之间呈二次函数关系;随着不锈钢丝股数增加,人工肌肉的收缩率和输出力增大,3股不锈钢丝性能最优,50g恒定载荷下收缩率达17%,输出力达0.67N。可为聚合物基人工肌肉的制备及应用提供一定理论依据。

Preparation and performance analysis of Pt-IPMC for driving bionic tulip

Based on the biological characteristics of tulip,the low driving voltage and fast response of ionic polymer metal composite(IPMC),we analyzed the fabrication,morphology and performance of the platinum IPMC(Pt-IPMC)and selected the right IPMC for driving bionic tulip.The preparation and performance of IPMC was analyzed first in this paper such as blocking force,output displacement and bending angle of IPMC under the different directed current voltage(DC).The optimal IPMC sample size and driving voltage were selected based on tulip blooming angles and the strain energy density of IPMC,which completed the blooming process of bionic tulip.The feasibility of IPMC used in driving bionic field was fully proved in this paper,which laid a foundation for the application of IPMC in driving biomimetic biological robots.