Optical Actuator Research Articles

An Optical Actuator Based on Gold‐Nanoparticle‐Containing Temperature‐Memory Semicrystalline Polymers

AbstractPhotoresponsive actuators based on semicrystalline poly(ethylene‐co‐vinyl acetate) (EVA) loaded with small amounts of gold nanoparticles (AuNPs) are described. Upon absorption of light (532 nm), the heat released by the AuNPs raises the temperature in the irradiated region to Tlight to melt crystallites with lower melting temperatures (Tm<Tlight), resulting in a contraction force on the sample sustained by the crystalline skeleton domains with Tm>Tlight . Once the light is turned off, the recrystallization of oriented chains in the actuation domains upon cooling gives rise to an expansion force. We show that the photoinduced contraction force, Tlight , and the speed for reaching Tlight can readily be adjusted, which makes EVA/AuNP a robust, fast optical actuation system tunable in both speed and magnitude. The material design can easily be extended to other temperature‐memory semicrystalline polymers in combination with various light‐absorbing and heat‐generating additives.

An Optical Actuator Based on Gold-Nanoparticle-Containing Temperature-Memory Semicrystalline Polymers.

Photoresponsive actuators based on semicrystalline poly(ethylene-co-vinyl acetate) (EVA) loaded with small amounts of gold nanoparticles (AuNPs) are described. Upon absorption of light (532 nm), the heat released by the AuNPs raises the temperature in the irradiated region to Tlight to melt crystallites with lower melting temperatures (Tm <Tlight ), resulting in a contraction force on the sample sustained by the crystalline skeleton domains with Tm >Tlight . Once the light is turned off, the recrystallization of oriented chains in the actuation domains upon cooling gives rise to an expansion force. We show that the photoinduced contraction force, Tlight , and the speed for reaching Tlight can readily be adjusted, which makes EVA/AuNP a robust, fast optical actuation system tunable in both speed and magnitude. The material design can easily be extended to other temperature-memory semicrystalline polymers in combination with various light-absorbing and heat-generating additives.

Experimental Investigation of Photostrictive Materials for MEMS Application

Micro-Electro-Mechanical-Systems (MEMS) is an emerging technology that integrates micromachined mechanical structures with integrated circuits (IC). During the last two decades, it has grown vastly as a prominent research area among scientists and engineers. Usually the main components of MEMS are sensors, actuators, and structures with all in microscale. A photostrictive mate-rial has high potential to be used in a MEMS application to develop an ad-vanced optical actuator. A strain is induced when a photostrictive material is il-luminated by high intensity light, which is known as photostriction. This phe-nomenon can be generally described as the combined effect of the photovoltaic effect and the converge-piezoelectric effect. When an incident light strikes a photostrictive material, a photovoltage is produced and this photovoltage develops strain in the material. Lanthanum modified lead zirconate titanate (Pb, La) (Zr, Ti) O3 ceramic doped with WO3, called PLZT, is one of the photostrictive ceramics which has an advantageous use as a wireless remote control over traditional actuators. Traditional actuators require wire connections to transmit the control signal; these wires yield noise via external electromagnetic fields. Whereas, PLZT actuators can transmit the control signal without wires which can eliminate possible noise due to the external electromagnetic field. In this current research, the photostrictive effect of a thin PLZT film on a silicon wafer is investigated experimentally. The transverse deflection of the PLZT optical actuator cantilever beam has been measured for stationary continuous light as well as for pulses of light using an optical chopper at various light intensities and focused locations. Results indicate that transverse deflection increases with the increase of light intensity. Also, the maximum transverse deflection at the free end of the cantilever beam for stationary light has been found to be three times larger than that for the pulses of light.

Characterization of Ferrofluid-Based Stimuli-Responsive Elastomers

Stimuli-responsive materials undergo physicochemical, and/or structural changes when a specific actuation is applied. They are heterogeneous composites, consisting of a non-responsive matrix where functionality is provided by the filler. Surprisingly, the synthesis of Polydimethylsiloxane (PDMS)-based stimuli-responsive elastomers (SRE) has seldomly been presented. Here we present the structural, biological, optical, magnetic and mechanical properties of several magnetic SRE (M-SRE) obtained by combining PDMS and isoparafin-based ferrofluid (FF). Independently of the FF concentration, results shown a similar aggregation level, with the nanoparticles (NP) mostly isolated (>60%). In addition to the superparamagnetic behaviour, the samples show no cytotoxicity except the sample with the highest FF concentration. Spectral response shows FF concentrations where both optical readout and magnetic actuation can simultaneously be used. The Young’s modulus increases with the FF concentration until the elastomeric network is distorted. Our results demonstrate that PDMS can host up to 24.6% FF. When applied to soft microsystems, a large displacement for relatively low magnetic fields (< 0.3 T) is achieved. The herein presented M-SRE characterization can be used for a large number of disciplines where magnetic actuation can be combined with optical detection, mechanical elements and biological samples.

A Review of Automated Microinjection Systems for Single Cells in the Embryogenesis Stage

Modern genetics research has resulted in significant advances in cell in vitro microinjection systems. Such systems provide biological and medical practitioners with high volume cell throughput and statistically relevant data. This paper provides the reader with a comprehensive review of the major research technologies used in automated cell microinjection and of their individual subsystems. Microinjection subsystems reviewed include machine vision, nonvision sensors and user interface (input), cell modeling, piercing mechanisms and injection control loop (control), cell holder and manipulator, and microinjection (output). The interdisciplinary technologies reviewed for microinjection sensing, automation, and control include microfluidic actuation, optical field actuation (optical trapping and optical guidance), electrical field actuation (electrorotation, electrowetting, and dielectrophoresis), and ultrasonic vibration. The survey concludes that research into automated microinjection systems will focus on reducing the scale of microinjection systems and developing appropriate controllers.

Engineering optical gradient force from coupled surface plasmon polariton modes in nanoscale plasmonic waveguides**Project supported by the National Natural Science Foundation of China (Grant No. 11474106) and the Natural Science Foundation of Guangdong Province, China (Grant No. 2016A030313439).

We explore the dispersion properties and optical gradient forces from mutual coupling of surface plasmon polariton (SPP) modes at two interfaces of nanoscale plasmonic waveguides with hyperbolic metamaterial cladding. With Maxwell’s equations and Maxwell stress tensor, we calculate and compare the dispersion relation and optical gradient force for symmetric and antisymmetric SPP modes in two kinds of nanoscale plasmonic waveguides. The numerical results show that the optical gradient force between two coupled hyperbolic metamaterial waveguides can be engineered flexibly by adjusting the waveguide structure parameters. Importantly, an alternative way to boost the optical gradient force is provided through engineering the hyperbolic metamaterial cladding of suitable orientation. These special optical properties will open the door for potential optomechanical applications, such as optical tweezers and actuators.

Molecular Dynamics Study on the Photothermal Actuation of a Glassy Photoresponsive Polymer Reinforced with Gold Nanoparticles with Size Effect.

We investigated the optical and thermal actuation behavior of densely cross-linked photoresponsive polymer (PRP) and polymer nanocomposites containing gold nanoparticles (PRP/Au) using all-atom molecular dynamics (MD) simulations. The modeled molecular structures contain a large number of photoreactive mesogens with linear orientation. Flexible side chains are interconnected through covalent bonds under periodic boundary conditions. A switchable dihedral potential was applied on a diazene moiety to describe the photochemical trans-to-cis isomerization. To quantify the photoinduced molecular reorientation and its effect on the macroscopic actuation of the neat PRP and PRP/Au materials, we characterized the photostrain and other material properties including elastic stiffness and thermal stability according to the photoisomerization ratio of the reactive groups. We particularly examined the effect of nanoparticle size on the photothermal actuation by varying the diameter of the nanofiller (10-20 Å) under the same volume fraction of 1.62%. The results indicated that the insertion of the gold nanoparticles enlarges the photostrain of the material while enhancing its mechanical stiffness and thermal stability. When the diameter of the nanoparticle reaches a size similar to or smaller than the length of the mesogen, the interfacial energy between the nanofiller and the surrounding polymer matrix does not significantly affect the alignment of the mesogens, but rather the adsorption energy at the interface generates a stable interphase layer. Hence, these improvements were more effective as the size of the gold nanoparticle decreased. The present findings suggest a wider analysis of the nanofiller-reinforced PRP composites and could be a guide for the mechanical design of the PRP actuator system.

적응광학계용 37채널 SiC 변형거울을 이용한 파면 보상

본 논문에서는 37채널을 갖는 적응광학계용 SiC(Silicon Carbide) 변형거울의 파면 보상 성능 검증에 관한 내용을 다룬다. 컴퓨터 시뮬레이션을 통해 SiC 변형거울의 파면 보상 성능을 예측하였고, 실제 closed-loop 적응광학계를 구성하여 파면 보상 성능을 확인 하였다. Closed-loop 적응광학계는 광원, 위상판, SiC 변형거울, 고속 샥-하트만 센서 그리고 제어용 컴퓨터로 구성되어있다. 회전하는 위상판에 의해 왜곡된 파면을 샥-하트만 센서로 측정하고, SiC 변형거울을 이용하여 왜곡된 파면을 보상해주는 시스템이다. 결과적으로 closed-loop 적응광학계에서 500 Hz의 속도로 PV(Peak-to-Valley) <TEX>$0.3{\mu}m{\sim}0.9{\mu}m$</TEX>, RMS(Root-Mean-Square) <TEX>$0.06{\mu}m{\sim}0.25{\mu}m$</TEX>의 왜곡된 파면을 PV <TEX>$0.1{\mu}m$</TEX>, RMS <TEX>$0.03{\mu}m$</TEX>이하로 보상시킬 수 있었다. In this paper, we deal with the wavefront compensation capability of a silicon carbide (SiC) deformable mirror (DM) with 37 actuators for adaptive optics. The wavefront compensation capability of the SiC DM is predicted by computer simulation and examined by actual experiments with a closed-loop adaptive optics system consistsing of a light source, a phase plate, a SiC DM, a high speed Shack-Hartmann sensor, and a control computer. Distortion of wavefront is caused by the phase plate in the closed-loop adaptive optics system. The distorted wavefront has a peak-to-valley (PV) wavefront error of <TEX>$0.3{\mu}m{\sim}0.9{\mu}m$</TEX> and root-mean-square (RMS) error of <TEX>$0.06{\mu}m{\sim}0.25{\mu}m$</TEX>. The high-speed Shack-Hartmann sensor measures the wavefront error of the distortion caused by the phase plate, and the SiC DM compensates for the distorted wavefront. The compensated wavefront has residual errors lower than <TEX>$0.1{\mu}m$</TEX> PV and <TEX>$0.03{\mu}m$</TEX> RMS. Consequently, we conclude that we can compensate for the distorted wavefront using the SiC DM in the closed-loop adaptive optics system with an operating frequency speed of 500 Hz.

Dispersion and optical gradient force from high-order mode coupling between two hyperbolic metamaterial waveguides

We analytically study dispersion properties and optical gradient forces of different-order transverse magnetic (TM) modes in two coupled hyperbolic metamaterial waveguides (HMMWs). According to Maxwell's equations, we obtain the dispersion relation of symmetric and antisymmetric modes, and calculate optical gradient forces of different-order modes by using Maxwell stress tensor. Numerical results show that the dispersion properties are dependent on the filling ratio, and the optical gradient forces of high-order TM modes are larger than the fundamental mode when the gap between two HMMWs is very narrow, but they weaken much faster than the case of low-order TM modes with the gap width increasing. In addition, the effects of the dielectric surrounding of waveguides on the coupling effect and optical gradient force are clarified. These properties offer an avenue for various optomechanical applications in optical sensors and actuators.

Effect of Tool Rotational and Al2O3 Powder in Electro Discharge Machining Characteristics of NiTi-60 Shape Memory Alloy

Nickel titanium is an intelligent alloy which are used in optical devices, thermal sensors, actuators, medical equipment and aerospace, because memory shape property, high strength, good creep and fatigue resistance. This alloy has features like the response to electrical stimulation, thermal, magnetic and mechanical stimulation. According to hardness and mechanical properties of this alloy, one of the ways it is used for machining, is EDM. EDM is one of the machining of precision and complex parts methods which material removal rate, tool wear rate, surface roughness and thickness of the recast layer one is very important in it. In this study the effect of current, voltage, pulse on time, pulse off time, tool rotational, Al2O3 powder, material removal rates, tool wear rate and surface roughness are examined. The results show that using Al2O3 powder and tool rotational along with increasing current intensity, pulse on time and voltage, increases the material removal rate. Rotation of the tool create a centrifugal force and Al2O3 powder increases the gap and the material removal rate. Rotation of the tool prevents spreading of the plasma channel and Al2O3 powder fills gap between tool and workpiece, decrease kinetic energy of ions and reduced tool wear rate. By adding powder Al2O3, rotation of the tool, reducing current intensity, voltage and time pulse, sparks get smaller and will have less penetration and surface roughness reduces.

Thermally Driven Photonic Actuator Based on Silica Opal Photonic Crystal with Liquid Crystal Elastomer.

We have developed a novel thermoresponsive photonic actuator based on three-dimensional SiO2 opal photonic crystals (PCs) together with liquid crystal elastomers (LCEs). In the process of fabrication of such a photonic actuator, the LCE precursor is infiltrated into the SiO2 opal PC followed by UV light-induced photopolymerization, thereby forming the SiO2 opal PC/LCE composite film with a bilayer structure. We find that this bilayer composite film simultaneously exhibits actuation behavior as well as the photonic band gap (PBG) response to external temperature variation. When the SiO2 opal PC/LCE composite film is heated, it exhibits a considerable bending deformation, and its PBG shifts to a shorter wavelength at the same time. In addition, this actuation is quite fast, reversible, and highly repeatable. The thermoresponsive behavior of the SiO2 opal PC/LCE composite films mainly derives from the thermal-driven change of nematic order of the LCE layer which leads to the asymmetric shrinkage/expansion of the bilayer structure. These results will be of interest in designing optical actuator systems for environment-temperature detection.

Optically triggered actuation in chitosan/reduced graphene oxide nanocomposites

Bio-compatible actuators which can work under optical stimulus have great future in bio-medical applications. In this work, chitosan/reduced graphene oxide (RGO) nanocomposite optical actuators were developed through a simple solvent casting technique. The photomechanical actuation of the composites is demonstrated under IR illumination. All samples exhibited contraction in length when exposed to IR light. The photomechanical stress and strain were found to increase with increasing RGO concentration. Photomechanical stress as high as 695kPa was achieved with 4wt.% RGO loading. Contrary to some other reported systems, the photomechanical stress decreased with the applied pre-strain. The actuation behaviour can be tuned either by altering the RGO content or applied pre-strain.

Research on the response improvement of optical actuation based on lead lanthanum zirconate titanate ceramics

Lead lanthanum zirconate titanate actuators taken as one type of photo-deformable actuators have been widely applied for micro-driven systems and active vibration control of photostrictive laminated flexible structures. However, the slow response of photodeformation of single patch lead lanthanum zirconate titanate actuator greatly affects its application. In this article, the main factors for the slow response of the lead lanthanum zirconate titanate actuator are investigated using experimental method. The increasing temperature during light on state and the residual photovoltage and photodeformation during light off state are considered as dominant factors causing the slow response of the lead lanthanum zirconate titanate actuator. To gain a better driving capability of lead lanthanum zirconate titanate actuator, some effective solutions through weakening the effect of increasing temperature and eliminating residual photovoltage and photodeformation are proposed and experimentally validated in this article. Considering the effective solutions proposed in this article, a novel optical driving mechanism based on multi-patches combination is proposed.

Cardiac Optogenetics: Enhancement by All-trans-Retinal.

All-trans-Retinal (ATR) is a photosensitizer, serving as the chromophore for depolarizing and hyperpolarizing light-sensitive ion channels and pumps (opsins), recently employed as fast optical actuators. In mammalian optogenetic applications (in brain and heart), endogenous ATR availability is not considered a limiting factor, yet it is unclear how ATR modulation may affect the response to optical stimulation. We hypothesized that exogenous ATR may improve light responsiveness of cardiac cells modified by Channelrhodopsin2 (ChR2), hence lowering the optical pacing energy. In virally-transduced (Ad-ChR2(H134R)-eYFP) light-sensitive cardiac syncytium in vitro, ATR supplements ≤2 μM improved cardiomyocyte viability and augmented ChR2 membrane expression several-fold, while >4 μM was toxic. Employing integrated optical actuation (470 nm) and optical mapping, we found that 1–2 μM ATR dramatically reduced optical pacing energy (over 30 times) to several μW/mm2, lowest values reported to date, but also caused action potential prolongation, minor changes in calcium transients and no change in conduction. Theoretical analysis helped explain ATR-caused reduction of optical excitation threshold in cardiomyocytes. We conclude that cardiomyocytes operate at non-saturating retinal levels, and carefully-dosed exogenous ATR can enhance the performance of ChR2 in cardiac cells and yield energy benefits over orders of magnitude for optogenetic stimulation.

Fundamental limits on the losses of phase and amplitude optical actuators

AbstractAmplitude and phase are the basic properties of all wave phenomena; as far as optical waves are concerned, the ability to act on these variables is at the root of a wealth of switching devices. To quantify the performance of an optical switching device, an essential aspect is to determine the tradeoff between the insertion loss and the amplitude or phase modulation depth. Here it is shown that every optical switching device is subject to such a tradeoff, intrinsically connected to the dielectric response of the materials employed inside the switching element itself. This limit finds its roots in fundamental physics, as it directly derives from Maxwell's equations for linear dielectrics, and is hence applicable to a wide class of optical components. Furthermore, a result is that concepts such as filtering, resonance, and critical coupling could be of advantage in approaching the limit. image

Aided manufacturing techniques and applications in optics and manipulation for ionic polymer-metal composites as soft sensors and actuators

AbstractRecently, ionic polymer-metal composites (IPMCs), which are becoming an increasingly popular material, have been used as soft actuators because of their inherent properties of light weight, flexibility, softness, especially efficient transformation from electrical energy to mechanical energy with large bending strain response under low activation voltage. This paper mainly focuses on a review on optical and micromanipulation applications of IPMCs as soft actuators. After presenting the general mechanism of sensing and actuating in IPMCs, recent progresses are discussed about the preparation process and practical technologies, especially for aided manufacturing techniques defined as the methods to fabricate IPMC into all kinds of shapes in terms of the demands, which are reviewed for the first time. Then, a number of recent IPMC applications for optical actuators, grippers and catheters are reviewed and investigated in this paper. Further developments and suggestions for IPMCs are also discussed. Extensive previous researches are provided for references in detail.

A low-cost mirror mount control system for optics setups

We describe a flexible, simple to build, low-cost, and computer-controlled optical mirror actuator system, developed for undergraduate research laboratories. Geared motors for hobby robotics are controlled by an Arduino microcontroller in combination with an H bridge to finely position mirror mount actuators. We present a graphical user interface based on the Python script language. The price of the fully controlled actuator system is only a small fraction of the price of a commercial system. It can be quickly implemented due to the use of open-hardware electronics. We discuss the performance of the system and give an outlook for future expansions and use in advanced optical setups.

The concept and realization of nanostructure fabrication using free-standing metallic wires with rapid thermal annealing

Free-standing metallic nanostructures are considered to be highly relevant to many branches of science and technology with applications of three dimensional metallic nanostructures ranging from optical reflectors, actuators, and antenna, to free-standing electrodes, mechanical, optical, and electrical resonators and sensors. Strain-induced out-of-plane fabrication has emerged as an effective method which uses relaxation of strain-mismatched materials. In this work, we report a study of the thermal annealing-induced shape modification of free-standing nanostructures, which was achieved by introducing compositional or microstructural nonuniformity to the nanowires. In particular gradient, segmented and striped hetero-nanowires were grown by focused-ion-beam-induced chemical vapor deposition, followed by rapid thermal annealing in a N2 atmosphere. Various free-standing nanostructures were produced as a result of the crystalline/grain growth and stress relief.

Thermo-mechanical characterization of optical thin films filters deposited onto shape memory alloy micro-actuators

Different optical thin films filters have been deposited by plasma techniques onto shape memory alloy micro-actuators controlled by the heating of laser irradiations. Thermomechanical cycles have been performed to investigate the stability of these optical filters. Excellent properties have been obtained with amorphous hydrogenated silicon/silica and amorphous hydrogenated silicon/plasma polymerized methacrylic acid-based filters; no degradation was observed after up to 50 000 cycles. Other silver/plasma polymerized methacrylic acid-based filters, which have a better selectivity and permit the use of more laser sources of different wavelengths for optical actuation, showed lower stability. The optical-filtering properties are lost during the thermomechanical cycles, due to a rearrangement of the silver atoms with heating. Thus, there is a trade-off between wavelength selectivity and the stability of the structures used for the optical control of the micro-actuators.

Optical neural interfaces.

Genetically encoded optical actuators and indicators have changed the landscape of neuroscience, enabling targetable control and readout of specific components of intact neural circuits in behaving animals. Here, we review the development of optical neural interfaces, focusing on hardware designed for optical control of neural activity, integrated optical control and electrical readout, and optical readout of population and single-cell neural activity in freely moving mammals.