Experimental Study and Model Analysis of the Performance of IPMC Membranes with Various Thickness

Ionic Polymer-Metal Composite （IPMC） is a new electro-active polymer, which has the advantages of light weight, flexibility, and large stroke with low driving voltage. Because of these features, IPMC can be applied to bionic robotic actuators, artificial muscles, as well as dynamic sensors. However, IPMC has the major drawback of low generative blocking force. In this paper, in order to enhance the blocking force, the Nation membranes with thickness of 0.22 mm, 0.32 mm, 0.42 mm, 0.64 mm and 0.8 mm were prepared by casting from liquid solution. By employing these Nation membranes, IPMCs with varying thickness were fabricated by electroless plating. The elastic modulus of the casted Nation membranes were obtained by a nano-indenter, and the current, the displacement and the blocking force were respectively measured by the apparatus for actuation test. Finally, the effects of the thickness on the performance of IPMC were analyzed with an electromechanical model. Experimental study and theory analysis indicate that as the thickness increases, the elastic modulus of Nation membrane and the blocking force of IPMC increase, however, the current and the displacement decrease.

The mechanisms of grain growth of Mg alloys:A review

Grain growth directly influences the plasticity and strength of Mg alloys.As the grain size decreases from the microscale to the nanoscale,the plasticity of Mg alloys continually increases,whereas the strength first increases and later decreases.These trends are observed because the plastic deformation mechanism changes from dislocation–twinning dominance to grain boundary dominance.In this study,the factors influencing grain growth,such as the temperature of plastic deformation/annealing,second-phase particles and solute atoms,are examined to aid effective control of the grain size.Additionally,the mechanisms of grain growth,typically induced by strain and thermal activation,are clarified.Strain-induced grain boundary migration is attributable to the difference in the strain energy stored in adjacent grains with high-density dislocations.Heat-induced grain boundary migration is driven by the difference in the energy of the grain boundary/subgrain boundary and boundary curvature.Abnormal grain growth can be induced by anisotropy of the strain energy,anisotropy of the grain boundary mobility,depinning of the second phase and high misorientation gradient.

Switchable shape memory polymer bio-inspired adhesive and its application for unmanned aerial vehicle landing

Controlled and switchable adhesion is commonly observed in biological systems.In recent years,many scholars have focused on making switchable bio-inspired adhesives.However,making a bio-inspired adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge.A Shape Memory Polymer Bio-inspired Adhesive(SMPBA)was successfully developed,well realizing high adhesion(about 337 kPa),relatively low preload(about90 kPa),high adhesion-to-preload ratio(about 3.74),high switching ratio(about 6.74),and easy detachment,which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect(SME).Furthermore,SMPBA exhibits adhesion strength of80–337 kPa on various surfaces(silicon,iron,and aluminum)with different roughness(Ra=0.021–10.280)because of the conformal contact,reflecting outstanding surface adaptability.The finite element analysis verifies the bending ability under different temperatures,while the adhesion model analyzes the influence of preload on contact area and adhesion.Furthermore,an Unmanned Aerial Vehicle(UAV)landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces.This study provides a novel switchable bio-inspired adhesive and UAV landing method.

基于AACSB和质量功能配置理念的课程教学质量提升研究

基于AACSB认证中的有关课程和教学的具体要求,将质量功能配置工具引入课程教学中,构建了课程教学体系设计的质量屋模型。以“新产品开发”课程的教学设计为例,具体分析模型的实际应用,并基于该模型提出相应的质量提升策略。

Black tantalic oxide submicro-particles coating on PEEK fibers woven into fabrics as artificial ligaments with photothermal antibacterial effect and osteogenic activity for promoting ligament-bone healing

Design of artificial ligaments possessing both osteogenic activity and antibacterial effect that promotes ligament-bone healing and prevents bacterial infection in bone tunnels for anterior cruciate ligament(ACL)reconstruction remains a significant challenge.In this study,black tantalic oxide(BTO)submicro-particles with oxygen vacancies and structure defects were fabricated by using traditional white tan-talic oxide(WTO)through magnesium thermal reduction(MTR)method,and BTO was coated on polyetheretherketone(PEEK)fibers(PKF),which were woven into fabrics(PBT)as artificial ligaments.PBT with BTO coating exhibited excellent photothermal performance,which possessed not only antibac-terial effects in vitro but also anti-infective ability in vivo.PBT with optimized surface properties(e.g.,submicro-topography and hydrophilicity)not only significantly facilitated rat bone mesenchymal stem cells(BMSC)responses(e.g.,proliferation and osteogenic differentiation)in vitro but also stimulated new bone formation for ligament-bone healing in vivo.The presence of oxygen vacancies and structure de-fects in BTO did not change the surface properties and osteogenic activity of BPT while displaying an outstanding photothermal antibacterial effect.In summary,BPT with osteogenic activity and photother-mal antibacterial effect promoted bone regeneration and prevented bacterial infection,thereby promoting ligament-bone healing.Therefore,PBT would have tremendous potential as a novel artificial ligament for ACL reconstruction.

Solid-state bonding process induced highly synergistic mechanical properties of 6061 Al alloy joint by shear deformation

Obtaining a highly synergistic mechanical property between joint and base metal(BM)in aluminum(Al)alloy is a chronic problem.In this work,shear bonding technology is applied to a commercial 6061 Al alloy.The results show that a flat and uniform joint interface is obtained.The joint presents a highly synergistic mechanical property compared with BM,whether after shear bonding or heat treatment.The joint coefficient reaches 95.6%after shear bonding and exceeds 100%after heat treatment,which is better than the traditional connection method of aluminum alloy.The high joint coefficient mainly originates from the well-linked joint and gradient grain structure.The gradient grain structure is beneficial to activate more slip systems to coordinate plastic deformation.Although the fine-grained structure is sacrificed after heat treatment,higher strength and joint coefficient are obtained due to the higher work hardening.This newly developed method has a large potential for application to the infinite rolling of Al alloy sheets and can also be used for Al alloy connection in automobile,aerospace,rail transportation,and other fields.The findings in this work can provide essential theoretical support and application reference for the shear connection of Al alloy.

Advanced Electro-active Dry Adhesive Actuated by an Artificial Muscle Constructed from an Ionic Polymer Metal Composite Reinforced with Nitrogen-doped Carbon Nanocages

An advanced electro-active dry adhesive, which was composed of a mushroom-shaped tibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite （IPMC） artificial muscle reinforced with nitrogen-doped carbon nanocages （NCNCs）, was developed to imitate the actuation of a gecko＇s toe. The properties of the NCNC-reinforced Nation membrane, the electro- mechanical properties of the NCNC-reinforced IPMC, and the related electro-active adhesion ability were investigated. The NCNCs were uniformly dispersed in the 0.1 wt% NCNC/Nafion membrane, and there was a seamless connection with no clear interface between the dry adhesive and the IPMC. Our 0.1 wt% NCNC/Nation-IPMC actuator shows a displacement and force that are 1.6 - 2 times higher than those of the recast Nafion-IPMC. This is due to the increased water uptake （25.39%） and tensile strength （24.5 MPa） of the specific 3D hollow NCNC-reinforced Nation membrane, as well as interactions between the NCNCs and the sulfonated groups of the Nation. The NCNC/Nation-IPMC was used to effectively actuate the mushroom-shaped dry adhesive. The normal adhesion forces were 7.85 raN, 12.1 mN, and 51.7 mN at sinusoidal voltages of 1.5 V, 2.5 V, and 3.5 V, respectively, at 0.1 Hz. Under the bionic leg trail, the normal and shear forces were approximately 713.5 mN （159 mN·cm^-2） and 1256.6 mN （279 mN·cm^-2）, respectively, which satisfy the required adhesion. This new electro-active dry adhesive can be applied for active, distributed actuation and flexible grip in robots.

Adhesion Characteristics of a Novel Synthetic Polydimethylsiloxane for Bionic Adhesive Pads

Materials with appropriate adhesive properties are suitable for the fabrication of bionic adhesive pads. In this study, a novel polydimethylsiloxane （PDMS） material enhanced with two types of crosslinkers, carbon nanotubes and graphene sheets, was fabricated. The Contact Angle （CA） and cross-sectional morphology of the new material were investigated and observed using a CA meter and Scanning Electron Microscopy （SEM）, respectively. CA measurements indicate that the surface energy of the novel material is twice that of the common PDMS material. SEM observations show that carbon nanotubes and graphene sheets are well dispersed in the polymer, a feature that improves the mechanical properties of the new material. The adhesive performance of this novel composite was tested on an in-house fabricated friction machine. Results show that at a preload of only 50 mN, the adhesion of the novel PDMS material is up to -3.7 times that of common PDMS. The maximum macroscale shear strength and normal adhesion reach 4 N·cm^-2 and 1 N·cm^-2, respectively. The adhesive capability of the material is maintained even after hundreds of times of repeated use. This novel material exhibits excellent adhesion, sufficiently high elastic modulus and high repeatability at low preloads.

Motion Control of Capsule-like Underwater Robot Utilizing the Swing Properties of Ionic Polymer Metal Composite Actuators

Ionic Polymer Metal Composite(IPMC)is a novel electrically actuated intelligent material with the advantages of big bending displacement,low driving voltage,flexible and so on.It has been recognized as one of the most attractive actuators with prospective applications for underwater robots and bionic organs.In this work,a capsule-like robot was introduced with the pectoral and caudal fins made of IPMC.By analyzing the properties of displacement response to square waves with different frequencies and low level voltages,it was found that performance of IPMC are frequency sensitive.Besides,when the absolute value of low level voltage decreases,IPMC could swing on one side with the decrease in amplitudes,whereas the amplitude at high level voltage fluctuates within small ranges at low frequencies.IPMC tip can approximately maintain when the frequency of driving signal around 30 Hz.Such properties were employed to control the locomotion of robot combining the motions of pectoral and caudal fin.Thus,the locomotions of swimming forward,turning and positioning were realized.

Optimized Bio-inspired Micro-pillar Dry Adhesive and Its Application for an Unmanned Aerial Vehicle Adhering on and Detaching from a Ceiling

Various bio-inspired dry adhesive materials have been investigated.In this work,lithography and silicon deep etching method were used to fabricate bio-inspired micro-pillar dry adhesive materials of which the parameters,such as side length,Height to Side length Aspect Ratio(HSAR),and inter-pillar Distance to Side length Aspect Ratio(DSAR)were comprehensively studied to obtain a dry adhesive with high adhesion.An orthogonal array method was designed and a series of fabrication experiments were conducted to identify optimum parameters,which resulted in a high normal adhesion of 2.98 N·cm^-2 and a shear adhesion of 9.59 N·cm^-2.An adhesion and desorption device was further designed on basis of the optimum dry adhesive,which enables an Unmanned Aerial Vehicle(UAV)to successfully adhere on and detach from a ceiling.This would allow an UAV to stay aloft for prolonged time,which could be invaluable to many applications,such as energy conservation and aerial detection.

The square rod-shaped ionic polymer-metal composite and its application in interventional surgical guide device

Ionic polymer-metal composite(IPMC)is an electro-active polymer material,which has many advantages such as small size,light weight,low driving voltage,large strain,and good biocompatibility.However,the conventional sheet IPMC has the shortcoming of only bending in the two-dimensional plane,which greatly limits the application of IPMC in the field of interventional surgery.In this work,a square rodshaped IPMC with multi-degree-of-freedom motion was fabricated,and the displacement and blocking force of the square rod-shaped IPMC in different directions are measured and analyzed under the DC voltage signal.An interventional catheter was designed using the square rod-shaped IPMC in order to achieve active guidance,and a simulation experiment platform and a model of human aorta were built to successfully complete the in vitro simulation experiment of interventional surgery,which preliminarily verified the feasibility of the square rod-shaped IPMC in the field of interventional surgery.

Effects of Cu^2＋ Counter Ions on the Actuation Performance of Flexible Ionic Polymer Metal Composite Actuators

The resistance of Ionic Polymer Metal Composite （IPMC） electrodes plays an important role in the actuation performance of IPMC actuators. Owing to crack formation on the surface of platinum electrode, the surface resistance of the electrode increases, which greatly limits its actuating performance. In this paper, we proposed a new method of dynamic self-repair electrodes by ex- changing Cu2＋ into the IPMC basement membrane. IPMC actuators with Cu2＋ were prepared and the actuation performance in the air was subsequently measured. Compared with conventional IPMC actuators containing Li＋ counter ions, those containing Cu2＋ counter ions exhibited 2 times - 3 times larger displacement and 2 times -3 times bigger blocking force. In the morphology observation, we found that many small copper particles scattered in the middle of cracks after several bending cycles, which leads to an obvious decrease in electrode resistance. In the Cyclic Voltammetry （CV） scan measurement, we observed that the oxidation reaction of copper alternates with reduction reaction of copper ions with the change of voltage polarity, which was a dynamic process. Based on these analyses, it is concluded that the presence of Cu2＋ can repair the damaged electrodes and induce lower electrode resistance, thus leading to the performance improvement of actuation.

Investigation of Ionic Polymer Metal Composite Actuators Loaded with Various Tetraethyl Orthosilicate Contents

Ionic Polymer Metal Composite （IPMC） can be used as an electrically activated actuator, which has been widely used in artificial muscles, bionic robotic actuators, and dynamic sensors since it has the advantages of large deformation, light weight, flexibility, and low driving voltage, etc. To further improve the mechanical properties of IPMC, this paper reports a new method for preparing organic-inorganic hybrid Nafion/SiO2 membranes. Beginning from cast Nation membranes, IPMCs with various tetraethyl orthosilicate （TEOS） contents were fabricated by electroless plating. The elastic moduli of cast Nation membranes were measured with nano indenters, the water contents were calculated, and the cross sections of Nation membranes were observed by scanning electron microscopy. The blocking force, the displacement, and the electric current of IPMCs were then measured on a test apparatus. The results show that the blocking force increases as the TEOS content gradually increases, and that both the displacement and the electric current initially decrease, then increase. When the TEOS content is 1.5%, the IPMC shows the best improved mechanical properties. Finally, the IPMC with the best improved performance was used to successfully actuate the artificial eye and tested.

Significantly Enhanced Actuation Performance of IPMC by Surfactant-Assisted Processable MWCNT/Nafion Composite

The performance of Ionic Polymer Metal Composite （IPMC） actuator was significantly enhanced by incorporating surfactant-assisted processable Multi-Walled Carbon Nanotubes （MWCNTs） into a Nation solution. Cationic surfactant Cetyl Trimethyl Ammonium Bromide （CTAB） was employed to disperse MWCNTs in the Nation matriX, forming a homogeneous and stable dispersion ofnanotubes. The processing did not involve any strong acid treatment and thus effectively preserved the excellent electronic properties associated with MWCNT. The as-obtained MWCNT/Nafion-IPMC actuator was tested in terms of conductivity, bulk and surface morphology, blocking force and electric current. It was shown that the blocking force and the current of the new IPMC are 2.4 times and 1.67 times higher compared with a pure Nation-based IPMC. Moreover, the MWCNT/IPMC performance is much better than previously reported Nafion-IPMC doped by acid-treated MWCNT. Such significantly improved performance should be attributed to the improvement of electrical property associated with the addition of MWCNTs without acid treatment.

Modeling of IPMC Cantilever＇s Displacements and Blocking Forces

The motion of an Ionic Polymer Metal Composite （IPMC） cantilever under a periodic voltage control is modeled. In our finite element 3D model, we follow both the free tip displacements and the blocking forces for various thicknesses and elastic constants of the ionomer membrane. It turns out that the maximum displacement of the free tip strongly depends on the value of the Young＇s modulus of the electrodes. Furthermore, the maximum blocking force, Fmax, increases with the thickness of the ionomer membrane. At constant values of Young＇s moduli of the electrodes and ionomer membrane thickness, if the Young＇s modulus of the ionomer membrane varies within the range from 0.2 MPa to 1 GPa, the change of Fmax is less than 10 %. The simulated maximal displacements, blocking forces and electrical currents are compared with the corresponding sets of ex- perimental data, respectively. Qualitative agreement between the simulated and the respective measured data profiles is ob- tained. Furthermore, it is found that the assumption of electrostatic interactions in the cation depleted region of the ionomer membrane has a negligible effect. The advantage of the model consists in its simplicity.

Review on Improvement,Modeling,and Application of Ionic Polymer Metal Composite Artificial Muscle

Recently,researchers have concentrated on studying ionic polymer metal composite(IPMC)artificial muscle,which has numerous advantages including a relatively large strain under low input voltage,flexibility,high response,low noise,light weight,and high driving energy density.This paper reports recent developments in IPMC artificial muscle,including improvement methods,modeling,and applications.Different types of IPMCs are described,along with various methods for overcoming some shortcomings,including improvement of Nafion matrix membranes,surface preparation of Nafion membranes,the choice of high-performing electrodes,and new electro-active polymers for enhancing the properties of IPMCs.IPMC models are also reviewed,providing theoretical guidance for studying the performance and applications of IPMCs.Successful applications such as bio-inspired robots,opto-mechatronic systems,and medical engineering are discussed.

Printing ionic polymer metal composite actuators by fused deposition modeling technology

In this work,we printed a Nafion precursor membrane by fused deposition modeling(FDM)rapid prototyping technology and further fabricated IPMCs by electroless plating.The ion-exchange capacity of the Nafion membrane was tested,and the morphology of IPMCs was observed.The electro-mechanical properties of IPMCs under AC voltage inputs were studied,and grasping experiments were performed.The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity.SEM observed that the thickness of the IPMC’s electrode layer was about 400 nm,and the platinum layer was tightly combined with the substrate membrane.When using a square wave input of 3.5 V and 0.1 Hz,the maximum current of IPMCs reached 0.30 A,and the displacement and blocking force were 7.57 mm and 10.5 mN,respectively.The new fabrication process ensures the good driving performance of the printed IPMC.And two pieces of IPMCs can capture the irregular objects successfully,indicating the feasibility of printing IPMCs by FDM technology.This paper provides a new and simple method for the fabrication of three-dimensional IPMCs,which can be further applied in flexible grippers and soft robotics.