Phase Change Actuator Research Articles

Wireless Miniature Magnetic Phase-Change Soft Actuators.

Wireless miniature soft actuators are promising for various potential high-impact applications in medical, robotic grippers, and artificial muscles. However, these miniature soft actuators are currently constrained by a small output force and low work capacity. To address such challenges, a miniature magnetic phase-change soft composite actuator is reported. This soft actuator exhibits an expanding deformation and enables up to a 70 N output force and 175.2 J g−1 work capacity under remote magnetic radio frequency heating, which are 106–107 times that of traditional magnetic soft actuators. To demonstrate its capabilities, a wireless soft robotic device is first designed that can withstand 0.24 m s−1 fluid flows in an artery phantom. By integrating it with a thermally-responsive shape-memory polymer and bistable metamaterial sleeve, a wireless reversible bistable stent is designed toward future potential angioplasty applications. Moreover, it can additionally locomote inside and jump out of granular media. At last, the phase-change actuator can realize programmable bending deformations when a specifically designed magnetization profile is encoded, enhancing its shape-programming capability. Such a miniature soft actuator provides an approach to enhance the mechanical output and versatility of magnetic soft robots and devices, extending their medical and other potential applications.

HaPouch: A Miniaturized, Soft, and Wearable Haptic Display Device Using a Liquid-to-Gas Phase Change Actuator

Wearable haptic displays can provide haptic information while allowing for free body movement. Among these haptic displays, pneumatic haptic displays have the advantages of flexibility and lightweight; however, they require bulky air tubes and a heavy air compressor. To solve this problem, we propose a wearable haptic display that uses a liquid-to-gas phase change actuator and a Peltier device as a way to reduce the size of the entire system. A low-boiling-point liquid is encapsulated in the flexible bladder of the actuator, and the vaporization of the liquid, which induces the inflation of the actuator, is controlled by the external Peltier device. In this study, we implemented a pressure sensor to monitor pressure inside the liquid-to-gas phase change actuator. The pressure measurement will contribute to controlling the generated normal force. First, we characterized the pressure response concerning the design of the liquid-to-gas phase change actuator. Next, we evaluated the output normal force of the haptic display and confirmed that the maximum output force reached a few newtons, which is a similar level to the off-the-shelf wearable haptic display devices. Finally, a sensory evaluation revealed that the experimental participants perceived the haptic stimulus to their fingertips provided by the proposed haptic display in a few seconds. According to the obtained results, the proposed haptic display can be applied to applications such as human interfaces to provide force, allowing for a response time of a few seconds.

Fully flexible liquid-to-gas phase change actuators with integrated liquid metal heaters

In recent years, soft robots have been attracting interest because of their potential for new application fields. Among soft actuators for soft robots, liquid-to-gas phase change actuators have the advantage of structural simplicity. However, the actuators require an external heater to vaporize a low boiling point liquid inside the actuator. The heater typically consists of a solid electrode that often reduces the durability and flexibility of the heater. In this study, we propose a small liquid-to-gas phase change actuator with an integrated liquid metal heater. A low boiling point liquid and liquid metal heater were encapsulated in a nylon-polyethylene bladder using wire molding. The proposed soft actuator has high flexibility and durability against bending because of the material used. We experimentally characterized actuators of different sizes with respect to the generated force, displacement, and time response. We also confirmed that the soft actuator could work even after bending 1000 times.

Performanceuntersuchung der Aktoreigenschaften/Performance investigation of PCA properties - High-strength aluminum as housing for high-performance phase change actuators (PCA)

Gehäuse aus der hochfesten Aluminiumlegierung EN AW-7075 versprechen eine Leistungssteigerung von paraffinbasierten Dehnstoffaktoren (DSA). Gegenüber Stahlgehäusen folgt eine höhere Wärmeleitfähigkeit und somit verkürzte Reaktionszeiten. Der geringere E-Modul und die höhere Elastizitätsgrenze vergrößern zudem die Stellwege. Diese Eigenschaften werden anhand numerischer Untersuchungen überprüft. Eine Ergebnisvalidierung sowie eine Diskussion der Herausforderungen in der Fertigung werden ebenfalls diskutiert.   Housings made of high-strength aluminum alloy EN AW-7075 suggest an increase in the performance of paraffin wax phase change actuators. Compared with steel housings, this results in higher thermal conductivity and thus shorter response times. The lower Young‘s modulus and the higher yield strength the more the actuator stroke will increase. These properties are verified by numerical investigations. A validation of results as well as a discussion of challenges in manufacturing are also presented.

Efficient validation of novel machine elements for capital goods

Novel machine elements often constitute the basis for innovative capital goods. While they are typically qualified in model experiments under predefined conditions, the real operating conditions in capital goods may differ considerably. In order to enable an agile development of innovative capital goods, an upgraded setup of the model experiments is proposed: Uncertainties in the installation conditions of the machine elements are represented by a new type of phase change actuators (PCA). The approach is demonstrated by a novel type of backlash-free high-load bearing.

Improvement of dynamic characteristics of manipulator driven by a gas-liquid phase-change actuator using an antagonistic drive

The goal of this research is to improve the dynamic characteristics of a manipulator composed of pneumatic artificial rubber muscles driven by gas-liquid phase change. Pneumatic actuators, such as pneumatic artificial rubber muscle (PARM) or rubber bellows, have been widely used in many industrial and research fields. They have merits of being compact and lightweight. However, the large size of the compressor driving the actuator is a problem. To overcome this, the authors researched soft actuators driven by the gas-liquid phase change (GLPC) of fluorocarbon. Fluorocarbon (C5F11NO) is a substance with a relatively low boiling point (50 °C) and a low heat of evaporation (104.65 kJ/kg). The heat of evaporation of water is 2260 kJ/kg. This paper presents the overview of an actuator driven by GLPC. Then, fabrication of a manipulator using the GLPC driven PARM, and details of experiments conducted to determine manipulator characteristics are given. To improve the dynamic characteristics of the manipulator, a force control method using the antagonistic drive of two PARMs is proposed, and experiments are conducted to validate the effectiveness of the proposed method.

Photothermally Driven Refreshable Microactuators Based on Graphene Oxide Doped Paraffin.

Actuators based on phase change materials (paraffin) can simultaneously produce large stroke length and large force due to thermal expansion, but the low thermal conductivity of paraffin requires high power input and long actuation time. The graphene oxide (GO) doped paraffin dynamic actuator addresses the key challenges in the design of thermal phase change actuators: Thermal conductivity and light absorbing are increased, and the response time is reduced compared to the standard phase change actuator designed with metal heating resistors. The thermal properties of GO-paraffin composites with varied loading amount are characterized to confirm the optimal loading amount of 1.0%. A multicell phase change actuator was integrated into a digital micromirror controlled optical system. A series of photothermally driven refreshable patterns were generated and confirmed with infrared imaging.

Maximising electro-mechanical response by minimising grain-scale strain heterogeneity in phase-change actuator ceramics

Phase-change actuator ceramics directly couple electrical and mechanical energies through an electric-field-induced phase transformation. These materials are promising for the replacement of the most common electro-mechanical ceramic, lead zirconate titanate, which has environmental concerns. Here, we show that by compositional modification, we reduce the grain-scale heterogeneity of the electro-mechanical response by 40%. In the materials investigated, this leads to an increase in the achievable electric-field-induced strain of the bulk ceramic of 45%. Compositions of (100–x)Bi0.5Na0.5TiO3–(x)BaTiO3, which initially possess a pseudo-cubic symmetry, can be tuned to undergo phase transformations to combined lower symmetry phases, thus decreasing the anisotropy of the transformation strain. Further, modelling of transformation strains of individual grains shows that minimum grain-scale strain heterogeneity can be achieved by precise control of the lattice distortions and orientation distributions of the induced phases. The current results can be used to guide the design of next generation high-strain electro-mechanical ceramic actuator materials.

An individual addressable and latchable actuator array for microfluidic systems

Microfluidic systems and applications are becoming more and more complex and therefore require a lot of individually addressable actuators and valves to guide the fluids inside the systems. In this paper, we present an actuator array based on a latchable phase change actuator, i.e. the solid/liquid phase change of the actuator medium is used to stabilize the two states of the actuator. The design of the actuator allows the individual control of a high number of actuators with only two external pressure lines. This is in contrast to conventional pressure-actuated membrane valves manufactured in soft elastomers such as PDMS (polydimethylsiloxane) which require increasing numbers of external pressure lines for a higher number of valves. First, we describe the general working principle of the actuator. The scalability of the actuator concept as well as the individual addressing is then demonstrated by means of two exemplary set-ups with four and twelve actuators. With the latter, we also show the suitability as a microvalve. We further characterized and optimized the response times of the actuator with respect to the heating power, the choice of the phase change medium as well as the volume of the actuator material used. We achieved switching times between the two stable states of the actuators in the range of 10 s.

Dynamic response of a thermally activated paraffin actuator

This paper considers a thermal phase change actuator filled with a solid–liquid phase change material (PCM), in which its ceiling wall can be thermally activated to move as a result of the volumetric changes associated with thermally induced melting and freezing processes of the PCM contained. Specifically, the present study aims to explore experimentally the dynamic response characteristics of the actuator’s movable wall during the melting process of a paraffin (n-Octadecane) as the PCM filled in a rectangular container. Melting experiments for the phase change actuator heated laterally at various isothermal wall temperatures with the solid PCM filled at different initial subcooling temperatures below its melting point have been undertaken to examine the melting heat transfer characteristics as well as the displacement behavior of its movable wall. The experimental results obtained reveal clearly that the melting progress of the PCM within the actuator has a dominant bearing on the induced moving speed and thus the total displacement of its movable wall. Moreover, the subcooling condition for the solid PCM filled in the actuator during the melting process may give rise to significant time lag for its thermally driven response, hence increasing the total time required for the solid PCM to be fully melted.

Development of a gas/liquid phase change actuator for high temperatures

Gas/liquid phase changes produce large volume changes in working fluids. These volume changes are used as the driving power sources in actuators such as micro-pumps and valves. Most of these actuators are utilized in ordinary temperature environments. However, the temperature range in which the phase change actuator can operate depends on the characteristics of the working fluid. We hypothesized that proper selection of the working fluid and the structure of the actuator can enable such actuators to be applied not only in ordinary environments but also in high temperature environments. Consequently, in this paper, we discuss the design and fabrication of a new gas/liquid phase change actuator for use in high temperature environments. Our proposed actuator consists of a bellow body, spring, heater, and working fluid. We used the Inconel super alloy, which is highly heat and corrosion resistant, for the bellow and moving parts of the actuator. For the working fluid, we prepared triethylene glycol, which has a boiling point of 287.3 °C and very low vapor pressure at ordinary temperature. As a result, our proposed actuator can be utilized in high temperature environments up to 300.0 °C. The results of several experiments conducted confirm that our proposed actuator generates 1.67 mm maximum displacement in a 300.0 °C atmospheric environment. In addition, we confirmed that the operation of the actuator is stable in that environment. Our results confirm that a gas/liquid phase change actuator can be used in high temperature environments.

Electric-field-induced paraelectric to ferroelectric phase transformation in prototypical polycrystalline BaTiO3

An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO3 at temperatures above the Curie point (TC) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above TC. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above TC, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm−1) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.

Special Issue on Robotics for Innovative Industry and Society

Robotics has become one of the most important automation technologies for industry and society. Robot components such as actuators and sensors, together with mechanisms and control systems, are being more and more combined with intelligent sensors in innovative industry design and fabrication. Robot technology is being applied in such fields as welfare, education, agriculture, and energy. Robot technology for welfare and nursing is being promoted by the government to increase lifestyle creativity as society ages. This special issue focuses on robotics in fields from manufacturing industries to societal needs. Papers ranging from robotics theory to robot application have been invited. Among the topics covered are robot mechanisms, robot components, actuators, sensors, and controllers, robot control theory, robotic systems, energy saving, industrial applications, automation, vehicles, entertainment, medicine, welfare and nursing applications, and robotics education. The 15 papers presented in this issue include actuators such as rubber artificial muscles or phase-change actuators, pneumatics, power assist devices such as assist glove and upper-limb assist devices, robotic suits, sensor fusion, omnidirectional locomotion, underwater robots, force display apparatuses, meal assistant robots, manufacturing applications of parallel-link mechanisms, surface polishing, and agricultural applications. These papers bring readers the latest state-of-the-art robot technologies useful in everything from analysis and design to control and applications in innovative industries. We thank the authors for their invaluable contributions and the reviewers for their advice – all of which have made this special issue both informative and entertaining.

Gas/Liquid Phase Change Actuator for Use in Extreme Temperature Environments

Manipulating materials exposed to extreme temperature environments presents numerous significant challenges. For example, steel industries require new methods for the direct handling of materials at temperatures greater than 1000°C, and material scientists require new methods for handling specimens at the helium temperature, where high-quality analysis must be performed with very low levels of thermal noise. However, conventional actuators do not work in such environments because of their low thermostability and, more importantly, the loss of the magnetic and piezoelectric properties of the actuator materials. For example, it is well known that magnetism and piezoelectricity completely disappear at temperatures exceeding the Curie point. This paper proposes a new working principle for actuators based on the gas/liquid phase change of working fluids. We show possibilities for the actuator design, including selections for temperature-resistant materials and working fluids at various temperatures. In addition, we discuss the design of the first prototype actuator, which worked successfully at 180°C by utilizing the gas/liquid phase change of water. The basic experimental results show significant potential for the actuator.

2201 作動流体の気液相変化を利用した高温環境用アクチュエータの開発 : トリエチレングリコールを作動流体とした300℃雰囲気下駆動実験(センサ・アクチュエータ(2))

Abstract: Manipulators which can be driven in high temperature environments have great possibilities of applications. Ordinary actuators are driven with functional materials, for example, electromagnet or piezo electric devices. Therefore, those actuators are difficult to be used in high temperature environments. We have proposed gas/liquid phase change actuator and tried to apply them to high temperature environments. We fabricate the prototype actuator which consists 0f Inconel alloy bellow, external spring, Tri Ethylene Glycol (TEG) as working fluid and heater. TEG has the boiling temperature under ordinary atmosphere around 287℃. Because of this high value of boiling point temperature, TEG is suitable for the actuator which will be driven in around 300℃temperature environments. In the 300℃ atmosphere, the actuator was driven by heater and it produced 2.4mm displacements. As a result of driving experiment, we confirm that our proposed actuator can be driven in 300℃ high temperature environment.

Experimental and numerical study of microchannel heater/evaporators for thermal phase-change actuators

The performance of thermal phase-change actuators is strongly affected by the design of their heater/evaporators. The use of microchannels to control the liquid working fluid via capillary forces promises one approach to optimize the operation of heater/evaporators and the performance of the actuators. An experimental and numerical study of heater/evaporators for phase-change actuators, based on open rectangular microchannels, is presented. The microchannel heater/evaporators consist of SU8 walls fabricated in a radial pattern on either silicon or silicon nitride membranes. The microchannels, of rectangular cross section, taper from a width of 80μm at their outer radius to a width of five microns at their inner radius, and have a constant depth of 40μm. The energy balance for the heater/evaporators is determined experimentally through measurements of electrical power dissipated as heat in a thin-film resistance heater, sensible heat transfer by conduction radially out of the evaporator, and latent heat transfer by evaporation from the microchannels themselves. A finite difference code is then used to calculate liquid flow pumped by capillary forces in the microchannels as well as sensible and latent heat transfer rates. The numerical code is shown to predict the experimental measurements well. The performance of this type of heater/evaporator for phase-change actuators is shown to be limited by two mechanisms: dry-out of the working fluid in the microchannels due to the capillary limit determines maximum evaporative mass transfer rates, while conduction heat losses out of the evaporators determines maximum evaporator efficiencies.

J114024 作動流体の相変化を利用した高温環境用アクチュエータの開発([J114-02]次世代アクチュエータシステム(2))

There are many actuators which are driven with phase change of working fluids developed. Almost of all them are driven in ordinary temperature environment. We developed new liquid-vapor phase change actuator for high temperature environment. The prototype of actuator which has cylinder structure has been driven in 180℃ temperature with water. Bellow type actuator have been driven under 300℃ temperature with TEG (TriEthylene glycol). In this paper we report that we have developed new bellow structure actuator. This new bellow actuator has an Inconel metal body and can change spring constant. We measured its static properties. We confirmed that this actuator can be driven under 300℃ environment and generated 682.2N force.

2P1-D05 シリンダ型気液相変化アクチュエータの試作と基本性能実験(アクチュエータの機構と制御(3))

From the perspective of minimum invasive surgery, research on the medical system utilized robot arm has been conducted. Surgical robot using pneumatic actuator has been successful in downsizing, but it need large peripheral devices to operate. Therefore, we propose a small and powerful gas-liquid phase-change actuator. The actuator driven by volume expansion during a phase-change from liquid phase to gas phase. The actuator can operate with a DC power supply only, so apparatus of the actuator are compact. We fabricated a cylinder type gas-liquid phase-change actuator utilized an air cylinder. This paper reports on that the basic performance of a cylinder type gas-liquid phase-change actuator.

Thermal phase change actuator for self-tracking solar concentration

We present a proof of principle demonstration of a reversible in-plane actuator activated by focused sunlight, and describe a concept for its use as a self-tracking mechanism in a planar solar concentrator. By actuating at the location of focused sunlight and splitting the solar spectrum for actuation energy, this phase change device aims to provide the adaptive mechanism necessary to efficiently couple concentrated solar light from a lens into a planar lightguide in a manner that is insensitive to incidence angle. As a preliminary demonstration we present a planar actuator array capable of in-plane deflections of >50 μm when illuminated with focused light from a solar simulator and demonstrate solar light activated frustrated total internal reflection (FTIR) with the actuator array. We further propose how this solar induced FTIR effect can be modified using a dichroic facet array to self-adaptively couple and concentrate solar light into a planar lightguide.

Power Output Force Generation by a MEMS Phase Change Actuator

A microelectromechanical-systems-based phase change actuator has been developed and tested for high-speed mechanical power output and force generation. This actuator is well suited for a variety of advanced devices like tactile displays or micro fluidic systems. The device features two thin membranes that bound a cavity filled with working fluid. The working fluid boils at low temperature. Two sizes of actuator are tested, an actuator with membrane sidelengths of 5 mm and an actuator with top membrane sidelength of 10 mm. Two top membrane materials are explored consisting of 2 μm thick silicon and 300 nm thick silicon nitride. Heat addition is through the lower membrane which is fabricated with novel capillary structures designed to increase the efficiency of actuator operation. The actuator is shown to produce up to 2.6 mW of mechanical power output and generate an applied force of 43 mN. Operating speeds up to 100 Hz are demonstrated.