Programmable Actuators Research Articles

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

AbstractA versatile, laser‐projector‐based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub‐100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light‐induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light‐responsive octopod, are demonstrated. The reported technique enables easy and cost‐effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.

Photothermal Surface Plasmon Resonance and Interband Transition‐Enhanced Nanocomposite Hydrogel Actuators with Hand‐Like Dynamic Manipulation

AbstractHydrogel actuators represent a powerful tool due to their ability to capture, move, and be manipulated, which has applications in diverse fields. The development of hydrogel actuators capable of localized movement, where only a part of the whole system moves, wireless remote control, and flexible shape‐changing is critical and challenging to fulfill their potential. Here, photothermal hydrogel actuators are designed and fabricated to accomplish a precise hand‐like manipulation of encapsulating and finger‐like one‐by‐one bending by light. A thermoresponsive poly(N‐isopropylacrylamide) (PNIPAm) active layer and a non‐thermoresponsive poly(acrylamide) passive layer are combined to generate a thermal‐expansion coefficient mismatch among the interface and this energy eventually transforms into a bending motion. As an energy transformation agent, the gold nanoparticles doped in the PNIPAm hydrogel absorb the light energy and transform it into thermalenergy effectively as a result of a surface plasmon resonance electron–phonon process and intrinsic interband transitions. The resulting nanocomposite actuators exhibit flexible, reversible motions and local hand‐like finger flexion driven by either flood illumination or local irradiation. The developed programmable actuators are expected to be an attractive candidate for the next generation of “smart” soft robots.

A Rewritable, Reprogrammable, Dual Light-Responsive Polymer Actuator.

We report on the fabrication of a rewritable and reprogrammable dual‐photoresponsive liquid crystalline‐based actuator containing an azomerocyanine dye that can be locally converted into the hydroxyazopyridinium form by acid treatment. Each dye absorbs at a different wavelength giving access to programmable actuators, the folding of which can be controlled by using different colors of light. The acidic patterning is reversible and allows the erasing and rewriting of patterns in the polymer film, giving access to reusable, adjustable soft actuators.

A Rewritable, Reprogrammable, Dual Light‐Responsive Polymer Actuator

AbstractWe report on the fabrication of a rewritable and reprogrammable dual‐photoresponsive liquid crystalline‐based actuator containing an azomerocyanine dye that can be locally converted into the hydroxyazopyridinium form by acid treatment. Each dye absorbs at a different wavelength giving access to programmable actuators, the folding of which can be controlled by using different colors of light. The acidic patterning is reversible and allows the erasing and rewriting of patterns in the polymer film, giving access to reusable, adjustable soft actuators.

Vapomechanically Responsive Motion of Microchannel-Programmed Actuators.

Materials that respond rapidly and reversibly to external stimuli currently stand among the top choices as actuators for real-world applications. Here, a series of programmable actuators fabricated as single- or bilayer elements is described that can reversibly respond to minute concentrations of acetone vapors. By using templates, microchannel structures are replicated onto the surface of two highly elastic polymers, polyvinylidene fluoride (PVDF) and polyvinyl alcohol, to induce chiral coiling upon exposure to acetone vapors. The vapomechanical coiling is reversible and can be conducted repeatedly over 100 times without apparent fatigue. If they are immersed in liquid acetone, the actuators are saturated with the solvent and temporarily lose their motility but regain their shape and activity within seconds after the solvent evaporates. The desorption of acetone from the PVDF layer is four times faster than its adsorption, and the actuator composed of a single PVDF layer maintains its ability to move over an acetone-soaked filter paper even after several days. The controllable and reproducible sensing capability of this smart material can be utilized for actuating dynamic elements in soft robotics.

In-Gel Direct Laser Writing for 3D-Designed Hydrogel Composites That Undergo Complex Self-Shaping.

Self‐shaping and actuating materials inspired by biological system have enormous potential for biosensor, microrobotics, and optics. However, the control of 3D‐complex microactuation is still challenging due to the difficulty in design of nonuniform internal stress of micro/nanostructures. Here, we develop in‐gel direct laser writing (in‐gel DLW) procedure offering a high resolution inscription whereby the two materials, resin and hydrogel, are interpenetrated on a scale smaller than the wavelength of the light. The 3D position and mechanical properties of the inscribed structures could be tailored to a resolution better than 100 nm over a wide density range. These provide an unparalleled means of inscribing a freely suspended microstructures of a second material like a skeleton into the hydrogel body and also to direct isotropic volume changes to bending and distortion motions. In the combination with a thermosensitive hydrogel rather small temperature variations could actuate large amplitude motions. This generates complex modes of motion through the rational engineering of the stresses present in the multicomponent material. More sophisticated folding design would realize a multiple, programmable actuation of soft materials. This method inspired by biological system may offer the possibility for functional soft materials capable of biomimetic actuation and photonic crystal application.

Programmable Actuation of Porous Poly(Ionic Liquid) Membranes by Aligned Carbon Nanotubes

A composite porous polymer membrane with aligned CNTs in its matrix is developed which exhibits programmable, anisotropic actuation towards organic vapors. The alignment of CNTs in multiple directions and the gradient porous structure of the membrane are critical for the actuation, and the actuating direction can be well controlled at a direction perpendicular to the longitudinal orientation of CNTs. The reversible actuation may be repeated for 300 cycles without obvious fatigue. These polymer composites are promising building blocks for a wide variety of applications such as sensors and actuators. The concept of programmable actuation succeeded here in a porous polymer mateial via complex orientation of CNTs reflects a new high level of control over physical motions that is applicable to a broad range of soft actuators.

4D fibrous materials: characterising the deployment of paper architectures

Deployment of folded paper architecture using a fluid medium as the morphing stimulus presents a simple and inexpensive methodology capable of self-actuation; where the underlying principles can be translated to develop smart fibrous materials capable of programmable actuations. In this study we characterise different paper architectures and their stimuli mechanisms for folded deployment; including the influence of porosity, moisture, surfactant concentration, temperature, and hornification. We observe that actuation time decreases with paper grammage; through the addition of surfactants, and when the temperature is increased at the fluid–vapour interface. There is a clear effect of hydration, water transport and the interaction of hydrogen bonds within the fibrous architecture which drives the deployment of the folded regions. The importance of fibre volume fraction and functional fillers in shape recovery was also observed, as well as the effect of a multilayer composite paper system. The design guidelines shown here will inform the development of synthetic fibrous actuators for repeated deployment.

Invitro selection technologies to enhance biomaterial functionality.

Cells make decisions and fate choices based in part on cues they receive from their external environment. Factors that affect the interpretation of these cues include the soluble proteins that are present at any given time, the cell surface receptors that are available to bind these proteins, and the relative affinities of the soluble proteins for their cognate receptors. Researchers have identified many of the biological motifs responsible for the high-affinity interactions between proteins and their receptors, and subsequently incorporated these motifs into biomaterials to elicit control over cell behavior. Common modes of control include localized sequestration of proteins to improve bioavailability and direct inhibition or activation of a receptor by an immobilized peptide or protein. However, naturally occurring biological motifs often possess promiscuous affinity for multiple proteins and receptors or lack programmable actuation in response to dynamic stimuli, thereby limiting the amount of control they can exert over cellular decisions. These natural motifs only represent a small fraction of the biological diversity that can be assayed by invitro selection strategies, and the discovery of "artificial" motifs with varying affinity, specificity, and functionality could greatly expand the repertoire of engineered biomaterial properties. This minireview provides a brief summary of classical and emerging techniques in peptide phage display and nucleic acid aptamer selections and discusses prospective applications in the areas of cell adhesion, angiogenesis, neural regeneration, and immune modulation.

Electromechanical Actuator Ribbons Driven by Electrically Conducting Spring-Like Fibers.

Electrically conducting fibers are woven into polymer ribbons to prepare electromechanical actuators. The ribbons generate a strain rate of more than 10(3) times that of typical electrochemical actuators, accompanied by a lower operating voltage and faster responsiveness compared to electrostatic and electrothermal actuators. Programmable actuation including bending, contraction, elongation, and rotation are shown with a high reversibility.

Bio-inspired wooden actuators for large scale applications.

Implementing programmable actuation into materials and structures is a major topic in the field of smart materials. In particular the bilayer principle has been employed to develop actuators that respond to various kinds of stimuli. A multitude of small scale applications down to micrometer size have been developed, but up-scaling remains challenging due to either limitations in mechanical stiffness of the material or in the manufacturing processes. Here, we demonstrate the actuation of wooden bilayers in response to changes in relative humidity, making use of the high material stiffness and a good machinability to reach large scale actuation and application. Amplitude and response time of the actuation were measured and can be predicted and controlled by adapting the geometry and the constitution of the bilayers. Field tests in full weathering conditions revealed long-term stability of the actuation. The potential of the concept is shown by a first demonstrator. With the sensor and actuator intrinsically incorporated in the wooden bilayers, the daily change in relative humidity is exploited for an autonomous and solar powered movement of a tracker for solar modules.

Optimization of Pathway Pattern Size for Programmable Biomolecule Actuation

We generalize a method for optimization of pattern size for an programmable actuation of magnetic beads, as biomolecule carriers, by analytically formulating the governing forces in terms of bead and pattern sizes. There is a good agreement between analytically calculated and numerically obtained forces, giving a validity of the analytical actuation force for the optimization of pattern size. The maximum actuation force is given at the phase angle of π/4 between the direction of magnetic field and the bead position, and the optimum radius of disk pattern is in the range of 2-5 times of bead radius, depending on the magnetization of the disk pattern under an external magnetic field.

MultiSense: proportional-share for mechanically steerable sensor networks

Steerable sensors, such as pan-tilt-zoom cam- eras and weather radars, expose programmable actuators to applications, which steer them to dictate the type, quality, and quantity of data they collect. Applications with dif- ferent goals steer these sensors in different directions. Although being expensive to deploy and maintain, existing steerable sensor networks allow only a single application to control them due to the slow speed of their mechanical actuators. To address the problem, we design MultiSense to enable fine-grained multiplexing by (1) exposing a virtual sensor to each application and (2) optimizing the time to context-switch between virtual sensors and satisfy requests. We implement MultiSense in Xen, a widely used virtual- ization platform, and explore how well proportional-share scheduling, along with extensions for state restoration, request batching and merging, and anticipatory scheduling, satisfies the unique requirements of steerable sensors. We present experiments for pan-tilt-zoom cameras and weather radars that show MultiSense efficiently isolates the per- formance of virtual sensors, allowing concurrent applica- tions to satisfy conflicting goals. As one example, we enable a tracking application to photograph an object moving at nearly 3 mph every 23 ft along its trajectory at a distance of 300 ft, while supporting a security application that photographs a fixed point every 3 s.

A software framework for coping with heterogeneity in the shopfloor

PurposeThe CIM framework pursues the integration of components in a manufacturing enterprise by means of computer systems. This, however, may be obstructed due to heterogeneity in the field: programmable controllers, robots, sensors and actuators, etc. in communications: different kinds of networks and/or field buses; and in the programming tools for all these devices. Thus a solution is needed to integrate heterogeneous software/hardware components in a well‐defined and flexible fashion. This paper seeks to address these issues.Design/methodology/approachThis paper proposes a metalanguage, called H, and a set of tools that serve for designing, implementing, deploying, and debugging distributed heterogeneous software on the shopfloor. The metalanguange includes fault‐tolerance and real‐time mechanisms, among other features.FindingsThe use of a framework that can integrate different software and hardware components enables the engineer to take advantage of the best features of each existing technology. The use of object‐oriented techniques, concurrent and distributed programming, and the isolation of heterogeneous parts, have also important benefits in the reusability and optimality of the solutions.Practical implicationsThe use of a metalanguage like H, that separates the parts of the application that depend on particular (heterogeneous) components from the parts that are portable, has, as a main implication, important improvements in the development time, effort, and cost of CIM projects.Originality/valueH is the first metalanguage coping with heterogeneity through the complete development cycle of software for manufacturing applications. It also provides a formal and well‐defined framework for future extensions.

Generation of quadratic potential force fields from flow fields for distributed manipulation

Distributed manipulation systems induce motions on objects through the application of many external forces. Many of these systems are abstracted as planar programmable force fields. Quadratic potential fields form a class of such fields that lend themselves to analytical study and exhibit useful stability properties. This paper introduces a new methodology to build quadratic potential fields with simple devices using the naturally existing phenomena of airflow, which is an improvement to the traditional use of the complicated programmable actuator arrays. It also provides a basis for the exploitation, in distributed manipulation, of natural phenomena like airflow, which require rigorous analysis and display stability difficulties. A demonstration and verification of the theoretical results for the special case of the elliptic field with airflows is also presented.

Some aspects of testing small‐scale masonry building models on simple earthquake simulators

AbstractThe basic aspects of testing small‐scale masonry building models on simple earthquake simulators are discussed. Since the scale effects represent a difficult problem to solve, the overall seismic behaviour of structural systems, and not the behaviour of structulal details, has been studied by testing the reduced‐sized models on a simple earthquake simulator. Accurate results regarding the dynamic behaviour and failure mechanism of the tested structures have been obtained by means of testing the relatively simple, adequately designed small‐scale masonry building models. A simple earthquake simulator capable of simulating the uni‐directional earthquake ground motion has been developed to study the seismic behaviour of masonry building models. Although a multipurpose programmable actuator was used to drive the shaking table, the comparison of the dynamic characteristics of the generated shaking‐table motion and the earthquake acceleration records used for the simulation of seismic loads showed an acceptable degree of correlation between the input and output seismic motion.