Microfabrication of piezoelectric MEMS based on thick LiNbO3single-crystal films.

Microfabrication procedure of piezoelectric micro electro-mechanical systems based on 5µm thick LiNbO3films on SiO2/Si substrate at wafer scale including deep dry etching of thick LiNbO3films by implementing pulsed mode of Ar/SF6gas was developed. In particular, two (YXlt)/128°/90°LiNbO3-Si cantilevers with tip mass were fabricated and characterized in terms of resonance frequency (511 and 817 Hz), actuation and acceleration sensing capabilities. The quality factor of 89.5 and the electromechanical coupling of 4.8% were estimated from measured frequency dependency of electrical impedance, fitted by using Butterworth-Van Dyke model. The fabricated piezoelectric micro-electro-mechanical systems have demonstrated highly linear displacement with good sensitivity (5.28 ± 0.02µm V-1) as a function of applied voltage and high sensitivity to vibrations of 667 mV g-1indicating a suitability of the structure for actuation purposes and for acceleration or frequency sensing with high precision, respectively.

A New Class of Single-Material, Non-Reciprocal Microactuators.

A crucial component in designing soft actuating structures with controllable shape changes is programming internal, mismatching stresses. In this work, a new paradigm for achieving anisotropic dynamics between isotropic end-states-yielding a non-reciprocal shrinking/swelling response over a full actuation cycle-in a microscale actuator made of a single material, purely through microscale design is demonstrated. Anisotropic dynamics is achieved by incorporating micro-sized pores into certain segments of the structures; by arranging porous and non-porous segments (specifically, struts) into a 2D hexagonally-shaped microscopic poly(N-isopropyl acrylamide) hydrogel particle, the rate of isotropic shrinking/swelling in the structure is locally modulated, generating global anisotropic, non-reciprocal, dynamics. A simple mathematical model is introduced that reveals the physics that underlies these dynamics. This design has the potential to be used as a foundational tool for inducing non-reciprocal actuation cycles with a single material structure, and enables new possibilities in producing customized soft actuators and modular anisotropic metamaterials for a range of real-world applications, such as artificial cilia.

Shape Memory Alloy (SMA)-Based Microscale Actuators with 60% Deformation Rate and 1.6 kHz Actuation Speed.

Shape memory alloys (SMAs) are widely utilized as an actuation source in microscale devices, since they have a simple actuation mechanism and high-power density. However, they have limitations in terms of strain range and actuation speed. High-speed microscale SMA actuators are developed having diamond-shaped frame structures with a diameter of 25 µm. These structures allow for a large elongation range compared with bulk SMA materials, with the aid of spring-like behavior under tensile deformation. These actuators are validated in terms of their applicability as an artificial muscle in microscale by investigating their behavior under mechanical deformation and changes in thermal conditions. The shape memory effect is triggered by delivering thermal energy with a laser. The fast heating and cooling phenomenon caused by the scale effect allows high-speed actuation up to 1600 Hz. It is expected that the proposed actuators will contribute to the development of soft robots and biomedical devices.

Shape Morphing Directed by Spatially Encoded, Dually Responsive Liquid Crystalline Elastomer Micro-Actuators.

Liquid crystalline elastomers (LCEs) with intrinsic molecular anisotropy can be programmed to morph shapes under external stimuli. However, it is difficult to program the position and orientation of individual mesogenic units separately and locally, whether in-plane or out-of-plane, since each mesogen is linked to adjacent ones through the covalently bonded polymer chains. Here, dually responsive, spindle-shaped micro-actuators are synthesized from LCE composites, which can reorient under a magnetic field and change the shape upon heating. When the discrete micro-actuators are embedded in a conventional and nonresponsive elastomer with programmed height distribution and in-plane orientation in local regions, robust and complex shape morphing induced by the cooperative actuations of the locally distributed micro-actuators, which corroborates with finite element analysis, are shown. The spatial encoding of discrete micro-actuators in a nonresponsive matrix allows to decouple the actuators and the matrix, broadening the material palette to program local and global responses to stimuli for applications including soft robotics, smart wearables, and sensors.

Thermally Induced Knudsen Forces for Contactless Manipulation of a Micro-Object.

In this paper, we propose that thermally induced Knudsen forces in a rarefied gas can be exploited to achieve a tweezer-like mechanism that can be used to trap and grasp a micro-object without physical contact. Using the direct simulation Monte Carlo (DSMC) method, we showed that the proposed mechanism is achieved when a heated thin plate, mounted perpendicularly on a flat substrate, is placed close to a colder object; in this case, a beam. This mechanism is mainly due to the pressure differences induced by the thermal edge flows at the corners of the beam and the thermal edge flow at the tip of the thin plate. Specifically, the pressure on the top surface of the beam is smaller than that on its bottom surface when the thin plate is above the beam, while the pressure on the right side of the beam is smaller than that on its left side when the thin plate is located near the right side of the beam. These differences in pressure generate a force, which attracts the beam to the plate horizontally and vertically. Furthermore, this phenomenon is enhanced when the height of the beam is shorter, such that the horizontal and vertical net forces, which attract the beam to the plate, become stronger. The mechanism proposed here was also found to depend significantly on the height of the beam, the temperature difference between the thin plate and the beam, and the Knudsen number.

Developments and Control of Biocompatible Conducting Polymer for Intracorporeal Continuum Robots.

Dexterity of robots is highly required when it comes to integration for medical applications. Major efforts have been conducted to increase the dexterity at the distal parts of medical robots. This paper reports on developments toward integrating biocompatible conducting polymers (CP) into inherently dexterous concentric tube robot paradigm. In the form of tri-layer thin structures, CP micro-actuators produce high strains while requiring less than 1 V for actuation. Fabrication, characterization, and first integrations of such micro-actuators are presented. The integration is validated in a preliminary telescopic soft robot prototype with qualitative and quantitative performance assessment of accurate position control for trajectory tracking scenarios. Further, CP micro-actuators are integrated to a laser steering system in a closed-loop control scheme with displacements up to 5 mm. Our first developments aim toward intracorporeal medical robotics, with miniaturized actuators to be embedded into continuum robots.