Rapid Actuation Research Articles

Electrochemical and electromechanical properties of high performance polymer actuators using multi-walled carbon nanotubes containing ruthenium oxide

Abstract The effects of ionic liquid (IL) on the electrochemical and electromechanical properties of actuators using a non-activated multi-walled carbon nanotube (MWCNT)-IL gel electrode containing ruthenium oxide (RuO2) were investigated. The electrochemical and electromechanical properties of actuators using non-activated MWCNT-IL gel electrodes containing RuO2 were compared to those of a single-walled carbon nanotube (SWCNT)-based actuator. The RuO2/MWCNT electrode containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI[BF4]) gives the largest double-layer capacitance. Moreover, the non-activated MWCNT polymer actuator containing RuO2 surpassed the performance of the only-MWCNT and only-SWCNT actuators in terms of the strain and maximum generated stress. The RuO2/MWCNT actuator containing EMI[CF3BF3] provided the largest strain and maximum generated stress. Both MWCNTs and RuO2 are required to produce a rapid and large response actuator that surpasses the performance of the only-SWCNT polymer actuator. The frequency dependence of the displacement response of the RuO2/MWCNT polymer actuator was also measured and could be successfully simulated using an electrochemical kinetic model. The simulation result for the frequency dependence of the electromechanical response of the RuO2/MWCNT actuators determined two parameters for the simulation: the strain at a limit of low frequency and the time constant.

Visible microactuation of a ferromagnetic shape memory alloy by focused laser beam

We used a focused laser beam to achieve large amplitude and localized controlled actuation in a microstructure made of a ferromagnetic shape memory alloy. Significant deformation (18 µm) was achieved at low laser power (20 mW) and the amplitude of actuation could be linearly controlled with the laser power. The rapid mechanical actuation shows no apparent sign of fatigue even after a million continuous oscillatory cycles. As a possible mechanism, we propose that the deformation of structure was induced by a combination of the thermal effect and the magnetic field of the incident laser light. This is possibly the first such reported visual evidence of microactuation of materials due to the optomagnetic field.

Feedback Control with Nominal Inputs for Agile Satellites Using Control Moment Gyros

Satellitesorbiting the Earthrequirelarge-angle andrapid rotational maneuverability. Controlmoment gyrosare expected to be applied to attitude control actuators of small agile satellites, because control moment gyros can generate high torque effectively. However, the control moment gyro hasa singularity problem that affects its energy consumption and rapid actuation. To solve the problem, a feedforward control logic using an energy-optimal path planned by a Fourier basis algorithm is proposed here. However, this logic alone cannot maintain precise control under actual errors and disturbances. Therefore, a feedback control system was also designed in order to acquire robustness against errors and disturbances. The designed system included in this paper is characterized by using a system’s limit state, which isa newly definedvariable, and is predicted by numerical integrals using nominal control inputs.Severalnumericalsimulationsandexperimentswerecarriedouttoverifythefeasibilityoftheproposedlogic in terms of the robustness, energy consumption, and the safe use of the control moment gyro.

Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuation

A new shape-memory nanocomposite that exhibits rapid electrical actuation capabilities is fabricated by incorporating self-assembly multiwalled carbon nanotube (MWCNT) nanopaper and magnetic CNTs into a styrene-based shape-memory polymer (SMP). The MWCNT nanopaper was coated on the surface to give high electrical conductivity to SMP. Electromagnetic CNTs were blended with and, vertically aligned into the SMP resin upon a magnetic field, to facilitate the heat transfer from the nanopaper to the underlying SMP. This not only significantly enhances heat transfer but also gives high speed electrical actuation.

Surface Acoustic Wave Driven Microfluidics – A Review

This paper presents a systematic overview on the recent works on surface acoustic wave (SAW) driven microfluidics. SAW microfluidics is based on acoustic streaming induced by leaky SAW radiation into a liquid. The development of this field attracts attention from microfluidic research community due to its rapid actuation, programmable capability, simple and yet efficient operation. In our paper, SAW microfluidic applications are categorized into droplet-based applications and continuous-flow applications. Droplet is actuated into unique behaviours depending on the applied SAW power. A wide range of droplet based applications have been employed utilizing these behaviours. In continuous-flow system, applications are further categorized based on the interaction of travelling SAW and standing SAW with the bulk liquid. Finally, future perspectives of SAW driven microfluidics are discussed

A simple smart wing actuator using Ni-Ti SMA

One way shape memory effect (SME) is not sufficient in the application of the automatic repeated actuation of the SMA wire because the actuator using SME cannot return to its initial shape after it cools down. In the present study, the two-way SME under residual stress is considered. An actuator using the two-way effect of SMA returns to its initial shape by increasing or decreasing the temperature of SMA under initial residual stress. Using the two-way effect, we manufactured a simple smart wing actuator which consists of the SMA wire and a torsional spring to induce variable residual stresses. The SMA wire after the specific training procedure in order for the actuator to be used for the repeated actuations without performance deteriorations in the specified actuation requirements was used. The simple smart wing actuator has been tested for repeated actuations in still-air as an environmental thermal condition for the practical aspect of its usage. The characteristics of actuator behavior according to operation thermal cycle duration time, i.e., the response characteristics for rapid actuation were investigated. By the application of the simple smart wing actuator using the SMA wire, SMA shows novel performance in repeated actuations.

Photopolymerized thiol-ene systems as shape memory polymers

In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advantageous properties due to the thiol-ene polymerization mechanism which results in the formation of a homogeneous polymer network with low shrinkage stress and negligible oxygen inhibition. The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts. The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40°C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response.

Monolithic polyaniline/polyvinyl alcohol nanocomposite actuators with tunable stimuli-responsive properties

High-performance monolithic actuators responding to acid/base were fabricated based on polyaniline (PANI) nanofibers and polyvinyl alcohol (PVA) nanocomposite. Flash-welding technique was adopted to endow PANI/PVA films with asymmetric structure, which drove rapid reversible actuation in acid/base. Compared with conventional PANI actuators, the PANI/PVA actuators were capable of providing tunable actuation degree and responsive rate, as well as enhanced mechanical properties and reversible repeatability. Moreover, the PANI/PVA actuators had much better recoverability in base than pure PANI nanofiber actuators. On the basis of PANI/PVA monolithic beam, we also fabricated PANI/PVA monolithic cubic boxes which showed tunable folding/unfolding response in acid/base via proper modulation. It is anticipated that the monolithic PANI/PVA nanocomposite actuators with tunable stimuli-responsive properties will have large potential for applications in micromechanical system, on-demand devices, chemical sensors and biomedical materials.

Conductive shape memory nanocomposites for high speed electrical actuation

A new shape memory nanocomposite that exhibits rapid electrical actuation capabilities is fabricated by incorporating continuous, non-woven carbon nanofibers (CNFs) into an epoxy based SMP matrix. The fiber morphology and nanometre size provide a percolating conductive network with a large interfacial area. This not only gives high electrical conductivity but also simultaneously enhances heat transfer and recovery stress.

First jump of microgel; actuation speed enhancement by elastic instability

Swelling-induced snap-buckling in a 3D micro hydrogel device, inspired by the insect-trapping action of Venus flytrap, makes it possible to generate astonishingly fast actuation. We demonstrate that elastic energy is effectively stored and quickly released from the device by incorporating elastic instability. Utilizing its rapid actuation speed, the device can even jump by itself upon wetting.

Crash safety through side impact protection

In the moments before a collision, only fractions of a second remain, in which to activate additional side impact protection and provide the passengers with better protection. As part of the European Aprosys project, a system has been developed, which can detect accidents at an early stage by using radar and video sensors and which uses a new type of very rapid actuator to activate the side impact protection. The project has been headed by engineers at Continental, the international automotive supplier.

Molecular Motor-Based Assays for Altered Nanomechanical Function of Ca2+-Regulatory Proteins in Cardiomyopathies

AbstractWe propose that a thermo-electrical control system for rapid and reversible actuation of biomolecular motors and their partner filaments can also be used to study molecular mechanisms of cardiovascular diseases. We have previously used this device to evaluate the temperature-dependence of unregulated (absence of cardiac Ca2+-regulatory proteins tropomyosin, α-Tm, and troponin, Tn) actin filament sliding powered by myosin motors, which hydrolyze ATP. These assays using the thermo-electric controller can also be applied to regulated thin filaments (F actin plus α-Tm and Tn) to obtain energetic parameters and functional correlates of structural stability at the level of single filaments. This allows us not only to examine Ca2+-dependent sliding of thin filaments, but also to test for altered function of clinically relevant mutations of cardiac myofilament proteins such as those identified in familial hypertrophic cardiomyopathy (FHC).

Microchip-based integration of cell immobilization, electrophoresis, post-column derivatization, and fluorescence detection for monitoring the release of dopamine from PC 12 cells

In this paper, we describe the fabrication and evaluation of a multilayer microchip device that can be used to quantitatively measure the amount of catecholamines released from PC 12 cells immobilized within the same device. This approach allows immobilized cells to be stimulated on-chip and, through rapid actuation of integrated microvalves, the products released from the cells are repeatedly injected into the electrophoresis portion of the microchip, where the analytes are separated based upon mass and charge and detected through post-column derivatization and fluorescence detection. Following optimization of the post-column derivatization detection scheme (using naphthalene-2,3-dicarboxaldehyde and 2-beta-mercaptoethanol), off-chip cell stimulation experiments were performed to demonstrate the ability of this device to detect dopamine from a population of PC 12 cells. The final 3-dimensional device that integrates an immobilized PC 12 cell reactor with the bilayer continuous flow sampling/electrophoresis microchip was used to continuously monitor the on-chip stimulated release of dopamine from PC 12 cells. Similar dopamine release was seen when stimulating on-chip versus off-chip yet the on-chip immobilization studies could be carried out with 500 times fewer cells in a much reduced volume. While this paper is focused on PC 12 cells and neurotransmitter analysis, the final device is a general analytical tool that is amenable to the immobilization of a variety of cell lines and analysis of various released analytes by electrophoretic means.

A low-cost, disposable card for rapid polymerase chain reaction

A low-cost, disposable card for rapid polymerase chain reaction (PCR) was developed in this work. Commercially available, adhesive-coated aluminum foils and polypropylene films were laminated with structured polycarbonate films to form microreactors in a card format. Ice valves [1] were employed to seal the reaction chambers during thermal cycling and a Peltier-based thermal cycler was configured for rapid thermal cycling and ice valve actuation. Numerical modeling was conducted to optimize the design of the PCR reactor and investigate the thermal gradient in the reaction chamber in the direction of sample thickness. The PCR reactor was experimentally characterized by using thin foil thermocouples and validated by a successful amplification of 10 copy of E. coli tuf gene in 27 min.

반복적인 작동을 위한 형상기억합금의 특성 실험과 거동 전산 모사

In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loadingunloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

Canonical Wnt signaling transiently stimulates proliferation and enhances neurogenesis in neonatal neural progenitor cultures

Canonical Wnt signaling triggers the formation of heterodimeric transcription factor complexes consisting of β-catenin and T cell factors, and thereby controls the execution of specific genetic programs. During the expansion and neurogenic phases of embryonic neural development canonical Wnt signaling initially controls proliferation of neural progenitor cells, and later neuronal differentiation. Whether Wnt growth factors affect neural progenitor cells postnatally is not known. Therefore, we have analyzed the impact of Wnt signaling on neural progenitors isolated from cerebral cortices of newborn mice. Expression profiling of pathway components revealed that these cells are fully equipped to respond to Wnt signals. However, Wnt pathway activation affected only a subset of neonatal progenitors and elicited a limited increase in proliferation and neuronal differentiation in distinct subsets of cells. Moreover, Wnt pathway activation only transiently stimulated S-phase entry but did not support long-term proliferation of progenitor cultures. The dampened nature of the Wnt response correlates with the predominant expression of inhibitory pathway components and the rapid actuation of negative feedback mechanisms. Interestingly, in differentiating cell cultures activation of canonical Wnt signaling reduced Hes1 and Hes5 expression suggesting that during postnatal neural development, Wnt/β-catenin signaling enhances neurogenesis from progenitor cells by interfering with Notch pathway activity.

Physical Limits and Design Principles for Plant and Fungal Movements

The typical scales for plant and fungal movements vary over many orders of magnitude in time and length, but they are ultimately based on hydraulics and mechanics. We show that quantification of the length and time scales involved in plant and fungal motions leads to a natural classification, whose physical basis can be understood through an analysis of the mechanics of water transport through an elastic tissue. Our study also suggests a design principle for nonmuscular hydraulically actuated structures: Rapid actuation requires either small size or the enhancement of motion on large scales via elastic instabilities.

ISOLATING DAMAGE FROM MECHANICAL HARVESTING OF APPLES

This research studied the performance of the ARS fruit-harvesting concept in relationship to apple removal efficiency and damage. There were no differences in apple removal efficiency or fruit quality between a single impulse or three rapid impulses when using the rapid displacement actuator (RDA) for fruit removal. In the canopy zone .300 mm (12 in.) from the impulse point of the RDA, removal was not significantly different between apples on short limbs and long/thin limbs. Removal outside that zone was lower and there was a significant difference between removal on short and long/thin limbs. The harvesting concept described in this article harvested 53% to 72% damage-free apples on five cultivars. Cuts and punctures were a serious problem, but bruising was also a factor limiting better quality. Apples growing inside the canopy were significantly more susceptible to damage than apples growing below the canopy. There were no significant differences in the amount of damage-free apples detached from short limbs and long/thin limbs.

Dynamic Flow Response Due to Motion of Partial-Span Gurney-Type Flaps

Uninhabited air vehicles are commonly designed with high-aspect-ratio wings, which can be susceptible to significant aeroelastic vibrations. These oscillations can result in a loss of control or structural failure, and new techniques are necessary to alleviate them. A multidisciplinary effort at Stanford developed a distributed flow control method that used small trailing-edge actuators, known as micro-trailing-edge effectors (MiTEs) to alter the aerodynamic loads at specific spanwise locations along an airplane wing. The actuators were based on a Gurney flap, which is a trailing-edge flap of small size and large deflection, allowing an increase in lift with a small drag penalty. The transient response caused by relatively rapid MiTE actuation was studied using particle image velocimetry in the near wake. The transient response was quasi-steady for dimensionless actuation times (tU∞/c) near unity. A shorter dimensionless actuation time of 0.2 produced a transient response with significant overshoot of the downwash velocity in the near wake. This indicated a nonmonotonic response of the aerodynamic loads for rapid actuation.

Susceptibility of the Stem Pull Area of Mechanically Harvested Apples to Blue Mold Decay and Its Control with a Biocontrol Agent.

A new harvester, which uses a rapid displacement actuator on the main scaffolds to remove apples from trees with narrow-inclined trellises, has shown good potential. With this technique, stem loss (stempulls) during harvest ranges from 20 to 57%, depending on the cultivar. This can create a potential point of entry for pathogens. We evaluated the susceptibility of the stem cavity area, with and without stems, to blue mold decay (Penicillium expansum) on three cultivars of mechanically harvested apples, and tested the effectiveness of the antagonist Pseudomonas syringae (used in BioSave 110) in controlling decay. Fruit with stempulls were more susceptible to blue mold decay than fruit with stems. On fruit with stempulls inoculated with P. expansum and stored for 2 months at 1°C, decay incidence was 0% on 'Pink Lady', 8.3% on 'Ace Spur Delicious', and 41% on 'Empire'. On fruit with stems, there was no decay on all three cultivars. P. syringae reduced decay on 'Empire' with stempulls to 3.3%, and no decay occurred on the other two cultivars. Similar trends were observed on fruit stored at 22°C for 14 days, but the incidence of decay was higher, and only 'Pink Lady' had no decay on the antagonist-treated fruit. Although mechanical harvesting can predispose the stem cavity to decay in some cultivars, this problem can be alleviated using biological control without resorting to the use of synthetic pesticides.