Min-Woo Han

A shape memory alloy–based soft morphing actuator capable of pure twisting motion

This article introduces a novel design for a soft morphing actuator capable of pure twisting motion through a pair of shape memory alloy wires embedded in a polydimethylsiloxane matrix at constant and opposite eccentricity across the cross section in opposite directions. This report introduces the design of the actuator, the manufacturing method, and experimental results for the twisting angle and twisting force when varying the dimensions of the matrix of the actuator. Afterward, a simple model is applied to verify the effect of matrix dimensions on the twisting angle of the actuator. The results show that there is an optimal actuator thickness for both the twisting angle and the twisting force of the actuator, that there is a trade-off between the twisting angle and the twisting force for the actuator’s thickness, and that a longer length is better for both metrics within the tested dimensions.

Woven type smart soft composite beam with in-plane shape retention

Shape memory alloy (SMA) wire embedded composites (SMAECs) are widely used as morphing structures in small-size and high-output systems. However, conventional SMAECs cannot keep deformed shapes without additional energy. In this paper, a new kind of smart structure named the woven type smart soft composite (SSC) beam is introduced, which is not only capable of morphing, but also maintaining its deformed shape without additional energy. The woven type SSC beam consists of two parts: woven wires and matrix. The selected woven wires are nitinol (Ni–Ti) SMA wires and glass fibers, while the matrix part is polydimethylsiloxane (PDMS). In order to evaluate the performance of the woven type SSC beam in areas such as in-plane deformation, blocking force and repeatability, a beam-shape specimen is prepared of size 100 mm (length) × 8 mm (width) ×3 mm (thickness). The fabricated SSC beam achieved 21 mm deformation and 16 mm shape retention. Blocking force was measured using a dynamometer, and was about 60 mN. In the repeatability test, it recovered almost the same position when its cooling time was 90 s more. Consequently, the woven type SSC beam can be applied to bio-mimicking, soft morphing actuators, consuming less energy than traditional SMAECs.

Blooming Knit Flowers: Loop-Linked Soft Morphing Structures for Soft Robotics

A loop-linked structure, which is capable of morphing in various modes, including volumetric transformation, is developed based on knitting methods. Morphing flowers (a lily-like, a daffodil-like, gamopetalous, and a calla-like flower) are fabricated using loop patterning, and their blooming motion is demonstrated by controlling a current that selectively actuates the flowers petals.

Design and Performance Evaluation of Soft Morphing Car-Spoiler

Automotive wings are considered to be aerodynamic devices which have a significant effect on the driving, braking and cornering performances by influencing the flow of fluids around the vehicle without changing the weight of the vehicle. The wings have developed from having a fixed shape to multi-sectional wings in order to amplify the advantages of their aerodynamic effect in specific situations such as cornering and braking. However, the multi-sectional wings based on flaps, ailerons, and slats have to modify their surface or camber using hinged parts. These discrete sections create aerodynamic losses during shape changes. In this paper, a morphing car-spoiler based on a reinforced elastomer capable of continuous self-actuation throughout its surface was applied to a small-scale vehicle without slotted parts or mechanical elements. The designed morphing car-spoiler consists of a woven type Smart Soft Composite (SSC) which was made by weaving Shape Memory Alloy (SMA) wires and glass fibers embedded in a polydimethylsiloxane (PDMS) polymeric soft matrix. The phase transformation from martensite to austenite of the SMA wires creates an axial load in the longitudinal direction resulting in symmetric bending of the spoiler. Using an open-blowing type wind tunnel, tests were conducted on the stand-alone spoiler to verify its aerodynamic effects. Furthermore, to evaluate its performance in practice, the morphing car-spoiler was mounted on a small-scale vehicle and tested in a closed-type wind tunnel. Results show that the morphing car-spoiler generates a downforce which increases the normal tire adhesion and that it is possible to adapt its shape for various situations such as cornering and braking.Copyright

Fabrication of Miniature High-Speed Actuator Capable of Biomimetic Flapping Motions

Beyond conventional military products, technologies in the defense industry sectors around the globe are integrated and fused with newly emerging technologies such as three-dimensional printing (3DP) and smart material fabrication. Acknowledging these trends, this study proposes a miniature high-speed actuator whose fabrication process entails 3DP, smart materials, and shape memory alloy. The manufactured actuator is 25 mm long and 5 mm wide in and weighs 2.5 g, having the optimal frequency in the range of 35-40 Hz. Force and deformation measurement were also conducted, resulting in the lift force of 0.18 N per second with a bending deformation of 5 mm.

Design and development of bio-mimetic soft robotic hand with shape memory alloy

Conventionally, many robotic hands have been studied to imitate dexterous movement of hand using rigid elements such as joint, links and mechanical actuators. Solid-robot needs complex system under well-controlled condition to show the performance. As an alternative way, soft robotics has been developed to achieve biological motion with compact structure. High adaptability and smooth actuation can be realized with compliant materials. In this research, we developed a prototype soft robotic hand using shape memory alloy (SMA) and woven type smart soft composite (SSC). First, the main components and actuation of hand are defined from the anatomy to build soft robotic hand. Then, woven type SSC based actuator is fabricated and tested as an artificial muscle. Third, a prototype of soft robotic hand is designed and built as followed by anatomical analysis. Finally, the actuation and grasping performance of the soft robot-hand are tested.