Test for the deep:magnetic loading characterization of elastomers under extreme hydrostatic pressures

Soft robot incarnates its unique advantages in deep-sea exploration,but grapples with high hydrostatic pressure’s unpredictable impact on its mechanical performances.In our previous work,a self-powered soft robot showed excellent work performance in the Mariana Trench at a depth of 11000 m,yet experienced notable degradation in deforming capability.Here,we propose a magnetic loading method for characterizing elastomer’s mechanical properties under extremely high hydrostatic pressure of up to 120 MPa.This method facilitates remote loading and enables in-situ observation,so that the dimensions and deformation at high hydrostatic pressure are obtained and used for calculations.The results reveal that the Young’s modulus of Polydimethylsiloxane(PDMS)monotonously increases with pressure.It is found that the relative increase in Young’s modulus is determined by its initial value,which is 8% for an initial Young’s modulus of 2200 kPa and 38% for 660 kPa.The relation between initial Young’s modulus and relevant increase can be fitted by an exponential function.The bulk modulus of PDMS is about 1.4 GPa at 20℃ and is barely affected by hydrostatic pressure.The method can quantify alterations in the mechanical properties of elastomers induced by hydrostatic pressure,and provide guidance for the design of soft robots which serve in extreme pressure environment.

Analysis of Heading Stability due to Interactions between Pectoral and Caudal Fins in Robotic Boxfish Locomotion

Investigating the interaction between fins can guide the design and enhance the performance of robotic fish.In this paper,we take boxfish as the bionic object and discuss the effect of coupling motion gaits among the two primary propulsors,pectoral and caudal fins,on the heading stability of the body.First,we propose the structure and control system of the bionic boxfish prototype.Second,using a one/two-way fluid–structure interaction numerical method,we analyse the key parameters of the prototype and discuss the influence of pectoral and caudal motion gaits on the hydrodynamic performance.Finally,effect of the pectoral and caudal interactions on heading stability of the prototype is systematically analyzed and verified in experiments.Results show that the course-deviating degree,oscillation amplitudes of yawing,rolling,and pitching exhibited by the prototype are smaller than that caused by single propulsor when the motion gaits of both pectoral and caudal fins are coordinated in a specific range.This paper reveals for the first time the effect of interactions between pectoral and caudal fins,on the stability of body's course by means of Computational Fluid Dynamics and prototype experiments,which provides an essential guidance for the design of robotic fish propelled by multi-fins.

Inhibition of Heterogeneous Nucleation in Water by Hydrogel Coating

Heterogeneous nucleation plays a critical role in the phase transition of water,which can cause damage in various systems.Here,we report that heterogeneous nucleation can be inhibited by utilizing hydrogel coatings to isolate solid surfaces and water.Hydrogels,which contain over 90%water when fully swelled,exhibit a high degree of similarity to water.Due to this similarity,there is a great energy barrier for heterogeneous nucleation along the water-hydrogel interface.Additionally,hydrogel coatings,which possess polymer networks,exhibit higher fracture energy and more robust adhesion to solid surfaces compared to water.This high fracture and adhesion energy acts as a deterrent for fracture nucleation within the hydrogel or along the hydrogel-solid interface.With a hydrogel layer approximately 100μm thick,the boiling temperature of water under atmospheric pressure can be raised from 100 to 108℃.Notably,hydrogel coatings also result in remarkable reductions in cavitation pressure on multiple solid surfaces.We have demonstrated the efficacy of hydrogel coatings in preventing damages resulting from acceleration-induced cavitation.Hydrogel coatings have the potential to alter the energy landscape of heterogeneous nucleation on the water-solid interface,making them an exciting avenue for innovation in heat transfer and fluidic systems.

Review of Soft Linear Actuator and the Design of a Dielectric Elastomer Linear Actuator

Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed various soft active devices with linear actuation.This paper reviews several soft linear actu ators,such as the dielec trie elastomer,t hermal responsive hydrogels,pneumatic artificial muscle,and conducting polymers.The actuation mechanisms and performances of these soft linear actuators are summarized.Based on the dielectric elastomer,we propose a design of a hybrid system with linear actuation,driven by both the electric motor and dielectric elasto mer cone.The elec tromechanical behaviors of the dielec trie elastomer cone have been investigated in both experiment and finite element analysis.This work may guide the further design of soft actuators and robots.

RATE DEPENDENT STRESS-STRETCH RELATION OF DIELECTRIC ELASTOMERS SUBJECTED TO PURE SHEAR LIKE LOADING AND ELECTRIC FIELD

The performance of dielectric elastomer （DE） transducers is significantly affected by viscoelastic relaxation-induced electromechanical dissipations. This paper presents an experi- mental study to obtain the rate dependent stress-stretch relation of DE membranes （VHBTM9473） subjected to pure shear like loading and electric loading simultaneously. Stretching rate depen- dent behavior is observed. The results also show that the tensile force decreases as the voltage increases. The observations are compared with predictions by a viscoelastic model of DE. This experiment may be used for further studies of dynamic electromechanical coupling properties of DEs.

Culture of patient-derived multicellular clusters in suspended hydrogel capsules for pre-clinical personalized drug screening

A personalized medication regimen provides precise treatment for an individual and can be guided by pre-clinical drug screening.The economical and high-efficiency simulation of the liver tumor microenvironment(TME)in a drug-screening model has high value yet challenging to accomplish.Herein,we propose a simulation of the liver TME with suspended alginate-gelatin hydrogel capsules encapsulating patient-derived liver tumor multicellular clusters,and the culture of patient-derived tumor organoids(PDTOs)for personalized pre-clinical drug screening.The hydrogel capsule offers a 3D matrix environment with mechanical and biological properties similar to those of the liver in vivo.As a result,18 of the 28 patient-derived multicellular clusters were successfully cultured as PDTOs.These PDTOs,along with hepatocyte growth factor(HGF)of non-cellular components,preserve stromal cells,including cancer-associated fibroblasts(CAFs)and vascular endothelial cells(VECs).They also maintain stable expression of molecular markers and tumor heterogeneity similar to those of the original liver tumors.Drugs,including cabazitaxel,oxaliplatin,and sorafenib,were tested in PDTOs.The sensitivity of PDTOs to these drugs differs between individuals.The sensitivity of one PDTO to oxaliplatin was validated using magnetic resonance imaging(MRI)and biochemical tests after oxaliplatin clinical treatment of the corresponding patient.Therefore,this approach is promising for economical,accurate,and high-throughput drug screening for personalized treatment.

X-Mechanics——An endless frontier

In contrast to the conventional wisdom that mechanics is a relatively mature subject, the new manifestation of mechanics in an extended or crossed form is unfolding. Mechanics is now powering all subjects, from physical sciences, life sciences to social sciences. We name this new phase for the development of mechanics X-Mechanics. The present article outlines the contents of X-Mechanics from four aspects: cross media, cross scales, cross compliances, and cross cyber/physical spaces. X-Mechanics constitutes an endless frontier of science and technology.

Electromechanical behavior of fiber-reinforced dielectric elastomer membrane

Based on its large deformation,light weight,and high energy density,dielectric elastomer(DE)has been used as driven muscle in many areas.We design the fiberreinforced DE membrane by adding fibers in the membrane.The deformation and driven force direction of the membrane can be tuned by changing the fiber arrangements.The actuation in the perpendicular direction of the DE membrane with long fibers first increases and then decreases by the increasing of the fiber spacing in the perpendicular direction.The horizontal actuation of the membrane decreases by decreasing the spacing of short fibers.In the membrane-inflating structure,the radially arranged fibers will break the axisymmetric behavior of the structure.The top area of the inflated balloon without fiber will buckle up when the voltage reaches a certain level.Finite element simulations based on nonlinear field theory are conducted to investigate the effects of fiber arrangement and verify the experimental results.This work can guide the design of fiber-reinforced DE.