A Prototype of a Biomimetic Mantle Jet Propeller Inspired by Cuttlefish Actuated by SMA Wires and a Theoretical Model for Its Jet Thrust

The cuttlefish have higher swimming speed and more maneuverability than most of the fish mainly benefiting from their unique jet propulsion mechanism, which is realized by the contraction and expansion of their flexible mantle. However it is difficult to mimic this jet propulsion mechanism using conventional electro-mechanical structures. In this paper, the musculature of the cuttlefish mantle and how the mantle flexibly contracts and expands were analyzed first. Then the Shape Memory Alloy（SMA） wires were chosen as the actuators and the soft silica gel was chosen as the body materials to develop a biomimetic mantle jet propeller. The SMA wires were embedded within the soft silica gel formed with cuttlefish mantle shape along the annular direction to mimic the circular muscles of cuttlefish mantle. The water was squeezed out the mantle cavity to form rear jets when the biomimetic mantle was contracted by SMA wires. A mechanical model and a thermal model were established to analyze the jet thrust and the jetting frequency. Theoretical analysis shows that the jet thrust is proportional to the square of the rate of change of SMA strain. Increasing the driving voltage can improve the rate of change of SMA strain, thus can improve both the jet thrust and the jetting frequency. However the j etting frequency is mainly restricted by the cooling of SMA wires. To maximize the jetting frequency, the optimal driving parameters for different driving voltage were calculated. The propulsion performance was tested and the results show that the jet thrust can increase with the driving voltage as predicted and the maximum average jet thrust is 0.14 N when the driving voltage is 25 V. The swimming test was carried out to verify the feasibility of the novel design. It is shown that the biomimetic jet propeller can swim with higher speed as the jet thrust and jetting frequency increase and the maximum speed can reach 8.76 cm·s^-1 （0.35 BL·s^-1） at a jetting frequency of 0.83 Hz.     

Gait Study and Pattern Generation of a Starfish-Like Soft Robot with Flexible Rays Actuated by SMAs

This paper presents the design and development of a starfish-like soft robot with flexible rays and the implementation of multi-gait locomotion using Shape Memory Alloy （SMA） actuators. The design principle was inspired by the starfish, which possesses a remarkable symmetrical structure and soft internal skeleton. A soft robot body was constructed by using 3D printing technology. A kinematic model of the SMA spring was built and developed for motion control according to displacement and force requirements. The locomotion inspired from starfish was applied to the implementation of the multi-ray robot through the flexible actuation induced multi-gait movements in various environments. By virtue of the proposed ray control patterns in gait transition, the soft robot was able to cross over an obstacle approximately twice of its body height. Results also showed that the speed of the soft robot was 6.5 times faster on sand than on a clammy rough terrain. These experiments demonstrated that the bionic soft robot with flexible rays actuated by SMAs and multi-gait locomotion in proposed patterns can perform successfully and smoothly in various terrains.     

Improvement of Artificial Foldable Wing Models by Mimicking the Unfolding/Folding Mechanism of a Beetle Hind Wing

<正> In an attempt to realize a flapping wing micro-air vehicle with morphing wings, we report on improvements to our previousfoldable artificial hind wing.Multiple hinges, which were implemented to mimic the bending zone of a beetle hind wing, weremade of small composite hinge plates and tiny aluminum rivets.The buck-tails of rivets were flared after the hinge plates wereassembled with the rivets so that the folding/unfolding motions could be completed in less time, and the straight shape of theartificial hind wing could be maintained after fabrication.Folding and unfolding actions were triggered by electrically-activatedShape Memory Alloy (SMA) wires.For wing folding, the actuation characteristics of the SMA wire actuator were modifiedthrough heat treatment.Through a series of flapping tests, we confirmed that the artificial wings did not fold back and arbitrarilyfluctuate during the flapping motion.     

Tensile properties of embryonic epithelia measured using a novel instrument

We present the first measurements of the tensile properties of embryonic epithelia, data that are crucial to understanding the mechanics of morphogenetic movements. Fine wires were glued to the surface of an intact, live embryo using cyanoacrylate glue, after which the epithelium between the wires was separated from the remainder of the embryo by microsurgery. The wires were then separated from each other in 0.1 microm steps under computer control in order to elongate the tissue at a constant true strain rate. Force was determined from the degree of bending in the wires, and a real-time, image-based feedback system corrected for reductions in elongation that would otherwise have been caused by wire flexure. The instrument was used to determine the tensile properties of epidermis and neuroepithelia from early-stage embryos of the axolotl (Ambystoma mexicanum), a type of amphibian. Monolayer specimens as small as 300 by 500 microm were elongated at physiological strain rates of 5-30% per hour, and the effects of developmental stage, epithelium type, specimen origin, direction of elongation and strain rate were investigated. True strains as high as 50% were observed before tearing began and equivalent moduli for the initial, linear portion of the load resultant versus strain curves ranged from 1 x 10(-3) to 8 x 10(-3) N/m.     

Development and Analysis of an Electrically Actuated Lower Extremity Assistive Exoskeleton

An electrically actuated lower extremity exoskeleton is developed,in which only the knee joint is actuated actively while other joints linked by elastic elements are actuated passively.This paper describes the critical design criteria and presents the process of design and calculation of the actuation system.A flexible physical Human-Robot-Interaction (pHRI) measurement device is designed and applied to detect the human movement,which comprises two force sensors and two gasbags attached to the inner surface of the connection cuff.An online adaptive pHRI minimization control strategy is proposed and implemented to drive the robotic exoskeleton system to follow the motion trajectory of human limb.The measured pHRI information is fused by the Variance Weighted Average (VWA) method.The Mean Square Values (MSV) of pHRI and control torque are utilized to evaluate the performance of the exoskeleton.To improve the comfort level and reduce energy consumption,the gravity compensation is taken into consideration when the control law is designed.Finally,practical experiments are performed on healthy users.Experimental results show that the proposed system can assist people to walk and the outlined control strategy is valid and effective.     

拉伸作用对成骨细胞粘附、铺展、粘弹性的影响

采用四点弯曲梁实验装置（自行研制）对离体培养的大鼠成骨细胞,施以拉伸应变影响,通过微管吸吮系统、显微摄录、计算机图像系统了解细胞的粘附、铺展行为和细胞的粘弹性变化,认识细胞形态、粘附力及变形性对机械刺激的响应。发现：（1）机械拉伸2h成骨细胞与基底粘附力以及细胞单位面积粘附力较对照组明显升高,但加载后期与对照无明显;（2）成骨细胞粘弹性较对照组略低;（3）加载24h(500με）实验组细胞增殖比对照组快。机械拉伸有成骨细胞生长,并可通过粘附、铺展调整、削减应变影响。     

Effect of Flexible Back on Energy Absorption during Landing in Cats： A Biomechanical Investigation

Cats are characterized by their excellent landing ability. During the landing, they extend and bend their flexible backs. This study was undertaken to examine the effect of flexible back on impact attenuation. We collected kinematic and ground reaction force data from cats performing self-initiated jump down at different heights. Based on these measurements, the mechanical energy and elastic back energy were calculated. Further, we derived a beam model to predict back stiffness from the morphology of the vertebral spines. We found that cat could actively modulate the bending level of flexible back and the landing angle at different heights, making some kinetic energy be stored briefly as elastic strain energy in the back. This mechanism allows cat to reduce the kinetic energy dissipated by limbs and improve the efficiency of energy absorption. These results can provide bio- logical inspiration for the design of a flexible spine on a landing robot, and we anticipated their use in the energy absorption equipments for planetary exploration.     

The effect of wire plane tilt and olive wires on proximal tibia fracture fragment stability and fracture site motion

To analyze the effect of the tilt angle relationship between the crossed wire plane and the bone axis on the stiffness of fine wire external fixation, load-deformation behavior was compared across different tilt angles (0 degree, 10 degrees, and 20 degrees) of the plane containing crossed smooth or olive wires under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. A tilt angle of 20 degrees with olive wires provided significantly greater stiffness compared to smooth wires at any angle in any loading condition (p < 0.05). A tilt angle of 20 degrees with olive wires was also significantly more stiff than a tilt angle of 0 degree with olive wires in any loading condition. In torsion, olive wires with 10 degrees and 20 degrees tilt were not significantly different, while in posterior bending olive wires with 10 degrees tilt were significantly stiffer than olive wires with 0 degree or 20 degrees tilt. With smooth wires, tilting the wire plane caused a decrease in stiffness in posterior bending, posteromedial bending, and torsion. Overall, the use of olive wires in conjunction with tilting the wire plane enhances the fixation stiffness for proximal tibia fractures while allowing more options for wire configurations that avoid neurovascular and musculotendinous structures, and wounds.     

A Novel Implementation of a Flexible Robotic Fin Actuated by Shape Memory Alloy

In this paper,study of a novel flexible robotic-fin actuated by Shape Memory Alloy (SMA) is presented.The developed robotic fin is capable of implementing various 3-Dimensional (3D) motions,which plays an important role in robot propulsion and maneuverability.Firstly,the morphological and mechanics parameters of a real pectoral fin from a carp are investigated.Secondly,a detailed design of the flexible pectoral fin driven by SMA is presented according to the previous morphological and mechanics analyses.Thirdly,a simplified theoretical model on the SMA fin plate is derived.The thermodynamics of the SMA plate and the relationship between curvature and phase transformation are analyzed.Finally,several simulations and model experiments are conducted according to the previous analyses.The results of the experiments are useful for the control of the robotic fin.The experimental results reveal that the SMA actuated fin ray has a good actuating performance.     

Laser micromarking technique in studying the negative gravitropism in pea stem

A laser micromarking technique on plant epidermis was developed to study how a plant can reduce the stress in bending behavior by controlling the growth and morphogenesis. The negative gravitropism in a pea seedling (Pisum sativum L.) was discussed based on the time-dependent displacement of laser marking points which were formed by spatially-selective laser ablation of the cuticle layer that covers the outer surface of a plant. The elongation of the stem in the horizontal direction was remarkable in the first half of the gravitropism. The elongation percentages of the stem length between laser-marking points at around upper surface, middle, and bottom surface were evaluated to be 2.57, 4.87, and 7.70%, respectively. The characteristic feature of the stem bending in gravitropism is the elongation even at the upper surface region, that is, inside of the bending. This is a different feature from cantilever beams for structural materials like metals and polymers, where the compression of the upper surface and elongation of the bottom surface are caused by bending. Another laser micromarking technique was developed to improve the resolution of a dot-matrix pattern by fluorescent material transfer to a plant through a masking film with a micro-hole matrix pattern. Similar time-dependent displacement behavior was observed for a fluorescent dot-marked stem showing a feedback control loop in the mechanical optimization. These results suggested that plants solve the problem of the stress in stem bending through growth. The laser micromarking is an effective method for studying the mechanical optimization in plants.     

Comparison of mechanical properties of orthodontic nickel-titanium wires]

Two packages each, containing 10 wires per package, of different batches of 25 different types of orthodontic archwires made of super-elastic nickel-titanium alloys measuring 0.41 x 0.56 mm2, were investigated. The wires were characterized by obtaining the following measurements at an ambient temperature of 37 degrees: a three-point bending test with the supporting points spaced 10 mm apart, and determination of the torque/bending angle curves using a pure bending test. The force/deflection curves provided the parameters characterizing the super-elastic unloading plateau: average force, slope and endpoint. From the torque/bending angle curves, the parameters average torque, plateau endpoint and the elasticity parameters were determined. Average force (0.8-4.5 N), endpoint (0.2-0.9 mm) and the slope of the unloading plateau (0.2-2.1 N/mm) of the three-point bending test clearly differed for individual wires. Significant differences were also seen for average torque (1.5-11.5 Nmm), unloading plateau endpoint (2.7-20.0 degrees) and elasticity parameters epsilon 4, E4, E5 and E6 in the pure bending test. Individual batches showed only minor differences. The results permit the conclusion to be drawn that super-elasticity is applicable to only a small portion of the wires examined. Although other wires showed super-elastic behaviour, the unloading plateaus has a force level of up to 6 N, and cannot be recommended for orthodontic application. The super-elastic plateau is often of use only for deflections greater than 1.5 mm. The use of super-elastic archwires made of nickel-titanium alloys makes sense only when the elastic properties of the respective wires are known. This makes the provision by the manufacturer of relevant data on the elastic properties of wires a necessity.     

Sequence-dependent dynamics in duplex DNA

The submicrosecond bending dynamics of duplex DNA were measured at a single site, using a site-specific electron paramagnetic resonance active spin probe. The observed dynamics are interpreted in terms of the mean squared amplitude of bending relative to the end-to-end vector defined by the weakly bending rod model. The bending dynamics monitored at the single site varied when the length and position of a repeated AT sequence, distant from the spin probe, were changed. As the distance between the probe and the AT sequence was increased, the mean squared amplitude of bending seen by the probe due to that sequence decreased. A model for the sequence-dependent internal flexural motion of duplex DNA, which casts the mean squared bending amplitudes in terms of sequence-dependent bending parameters, has been developed. The best fit of the data to the model occurs when the (AT)(n) basepairs are assumed to be 20% more flexible than the average of the basepairs within the control sequence. These findings provide a quantitative basis for interpreting the kinetics of biological processes that depend on duplex DNA flexibility, such as protein recognition and chromatin packaging.     

Bending continuous structures with SMAs: a novel robotic fish design

In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed.     

Flexible Na/K‐Ion Full Batteries from the Renewable Cotton Cloth–Derived Stable,Low‐Cost,and Binder‐Free Anode and Cathode

Flexible Na/K‐ion batteries (NIBs/KIBs) exhibit great potential applications and have drawn much attention due to the continuous development of flexible electronics. However, there are still many huge challenges, mainly the design and construction of flexible electrodes (cathode and anode) with outstanding electrochemical properties. In this work, a unique approach to prepare flexible electrode is proposed by utilizing the commercially available cotton cloth–derived carbon cloth (CC) as a flexible anode and the substrate of a cathode. The binder‐free, self‐supporting, and flexible cathodes (FCC@N/KPB) are prepared by growing Prussian blue microcubes on the flexible CC (FCC). Na/K‐ion full batteries (FCC//FCC@N/KPB) are assembled by using FCC and FCC@N/KPB as anode and cathode, respectively. Electrochemical performance, mechanical flexibility, and practicability of FCC//FCC@N/KPB Na/K‐ion full batteries are evaluated in both coin cells and flexible pouch cells, demonstrating their superior energy‐storage properties (excellent rate performance and cycling stability) and remarkable flexibility (they can work under different bending states). This work provides a new and profound strategy to design flexible electrodes, promoting the development of flexible NIBs/KIBs to be practical and sustainable.     

Membrane protein extraction and purification using partially-esterified SMA polymers

Styrene maleic acid (SMA) polymers have proven to be very successful for the extraction of membrane proteins, forming SMA lipid particles (SMALPs), which maintain a lipid bilayer around the membrane protein. SMALP-encapsulated membrane proteins can be used for functional and structural studies. The SMALP approach allows retention of important protein-annular lipid interactions, exerts lateral pressure, and offers greater stability than traditional detergent solubilisation. However, SMA polymer does have some limitations, including a sensitivity to divalent cations and low pH, an absorbance spectrum that overlaps with many proteins, and possible restrictions on protein conformational change. Various modified polymers have been developed to try to overcome these challenges, but no clear solution has been found. A series of partially-esterified variants of SMA (SMA 2625, SMA 1440 and SMA 17352) has previously been shown to be highly effective for solubilisation of plant and cyanobacterial thylakoid membranes. It was hypothesised that the partial esterification of maleic acid groups would increase tolerance to divalent cations. Therefore, these partially-esterified polymers were tested for the solubilisation of lipids and membrane proteins, and their tolerance to magnesium ions. It was found that all partially esterified polymers were capable of solubilising and purifying a range of membrane proteins, but the yield of protein was lower with SMA 1440, and the degree of purity was lower for both SMA 1440 and SMA 17352. SMA 2625 performed comparably to SMA 2000. SMA 1440 also showed an increased sensitivity to divalent cations. Thus, it appears the interactions between SMA and divalent cations are more complex than proposed and require further investigation.     

Penalized Multimarker vs. Single-Marker Regression Methods for Genome-Wide Association Studies of Quantitative Traits

The data from genome-wide association studies (GWAS) in humans are still predominantly analyzed using single-marker association methods. As an alternative to single-marker analysis (SMA), all or subsets of markers can be tested simultaneously. This approach requires a form of penalized regression (PR) as the number of SNPs is much larger than the sample size. Here we review PR methods in the context of GWAS, extend them to perform penalty parameter and SNP selection by false discovery rate (FDR) control, and assess their performance in comparison with SMA. PR methods were compared with SMA, using realistically simulated GWAS data with a continuous phenotype and real data. Based on these comparisons our analytic FDR criterion may currently be the best approach to SNP selection using PR for GWAS. We found that PR with FDR control provides substantially more power than SMA with genome-wide type-I error control but somewhat less power than SMA with Benjamini–Hochberg FDR control (SMA-BH). PR with FDR-based penalty parameter selection controlled the FDR somewhat conservatively while SMA-BH may not achieve FDR control in all situations. Differences among PR methods seem quite small when the focus is on SNP selection with FDR control. Incorporating linkage disequilibrium into the penalization by adapting penalties developed for covariates measured on graphs can improve power but also generate more false positives or wider regions for follow-up. We recommend the elastic net with a mixing weight for the Lasso penalty near 0.5 as the best method.     

Polymer actuator valves toward controlled drug delivery application

A novel controlled drug delivery system in which drug release is achieved by electrochemically actuating an array of polymeric valves on a set of drug reservoirs has been developed. The valves are bilayer structures, made in shape of a flap hinged on one side to a valve seat, consisting of thin films of evaporated gold and electrochemically deposited polypyrrole (PPy). Drugs (dry or wet) were pre-stored in an array of these reservoirs and their release is accomplished by bending the bilayer flaps away from the substrate with a small applied bias. In vitro color dye release experiment has been conducted. Seventy-five percent less energy consumption was achieved with this bilayer polymer valve design to open a same size reservoir compared to metal-corrosion based valves. Complex release patterns such as multiple drug pulsatile release and continuous linear release have been successfully implemented through flexible control of valve actuation sequence. These valves can be actuated under closed-loop-control of sensors responding to a specific biological or environmental stimulus, leading to potential applications in advanced responsive drug delivery systems.     

Maturation antigen of the mouse sperm flagellum. I. Analysis of its secretion, association with sperm, and function

We report here recent findings on the sperm maturation antigen SMA4, which is secreted by holocrine cells of the distal caput epididymis and binds to the flagellar surface of mouse sperm during epididymal transit. Washed sperm from the caput and corpus epididymides of mice were examined by immunofluorescence and SDS-PAGE using wheat germ agglutinin, which binds specifically to SMA4 as a primary probe. Results indicate that sperm first exhibit WGA reactivity on their flagellae in the region of the distal caput, and that the appearance of WGA receptors is due to the binding of a 54-Kd glycoprotein (SMA4) to the cell surface. Extracts of epididymis containing SMA4 were tested for their ability to bind to the surfaces of caput and corpus sperm. Caput sperm surfaces bound SMA4 in a temperature-independent manner, and binding occurred in the presence of enzyme inhibitors, suggesting a nonenzymatic process. Biochemical studies revealed that SMA4 contains disulfide bonds which stabilize it on the sperm surface and restrict its mobility. Terminal carbohydrate residues of the molecule are sialic acids. The addition of SMA4 to caput sperm flagellae prevented tail-to-tail agglutination, normally seen when caput sperm are diluted into saline; and SMA4 was able to disperse clumps of agglutinated caput sperm. The data suggest that a primary function of SMA4 is to prevent tail-to-tail agglutination of sperm during storage in the epididymis.     

Minimum Membrane Bending Energies of Fusion Pores

Membranes fuse by forming highly curved intermediates, culminating in structures described as fusion pores. These hourglass-like figures that join two fusing membranes have high bending energies, which can be estimated using continuum elasticity models. Fusion pore bending energies depend strongly on shape, and the present study developed a method for determining the shape that minimizes bending energy. This was first applied to a fusion pore modeled as a single surface and then extended to a more realistic model treating a bilayer as two monolayers. For the two-monolayer model, fusion pores were found to have metastable states with energy minima at particular values of the pore diameter and bilayer separation. Fusion pore energies were relatively insensitive to membrane thickness but highly sensitive to spontaneous curvature and membrane asymmetry. With symmetrical bilayers and monolayer spontaneous curvatures of ?0.1 nm^?1 (a typical value) separated by 6 nm (closest distance determined by repulsive hydration forces), fusion pore formation required 43–65 kT. The pore radius of ~2.25 nm fell within the range estimated from conductance measurements. With bilayer separation >6 nm, fusion pore formation required less energy, suggesting that protein scaffolds can promote fusion by bending membranes toward one another. With nonzero spontaneous monolayer curvature, the shape that minimized the energy change during fusion pore formation differed from the shape that minimized its energy after it formed. Thus, a nascent fusion pore will relax spontaneously to a new shape, consistent with the experimentally observed expansion of nascent fusion pores during viral fusion.     

Role of the membrane cortex in neutrophil deformation in small pipets.

The simplest model for a neutrophil in its "passive" state views the cell as consisting of a liquid-like cytoplasmic region surrounded by a membrane. The cell surface is in a state of isotropic contraction, which causes the cell to assume a spherical shape. This contraction is characterized by the cortical tension. The cortical tension shows a weak area dilation dependence, and it determines the elastic properties of the cell for small curvature deformations. At high curvature deformations in small pipets (with internal radii less than 1 micron), the measured critical suction pressure for cell flow into the pipet is larger than its estimate from the law of Laplace. A model is proposed where the region consisting of the cytoplasm membrane and the underlying cortex (having a finite thickness) is introduced at the cell surface. The mechanical properties of this region are characterized by the apparent cortical tension (defined as a free contraction energy per unit area) and the apparent bending modulus (introduced as a bending free energy per unit area) of its middle plane. The model predicts that for small curvature deformations (in pipets having radii larger than 1.2 microns) the role of the cortical thickness and the resistance for bending of the membrane-cortex complex is negligible. For high curvature deformations, they lead to elevated suction pressures above the values predicted from the law of Laplace. The existence of elevated suction pressures for pipets with radii from 1 micron down to 0.24 micron is found experimentally. The measured excess suction pressures cannot be explained only by the modified law of Laplace (for a cortex with finite thickness and negligible bending resistance), because it predicts unacceptable high cortical thicknesses (from 0.3 to 0.7 micron). It is concluded that the membrane-cortex complex has an apparent bending modulus from 1 x 10(-18) to 2 x 10(-18) J for a cortex with a thickness from 0.1 micron down to values much smaller than the radius of the smallest pipet (0.24 micron) used in this study.