Power Amplification for Jumping Soft Robots Actuated by Artificial Muscles.

Robots composed of soft materials can passively adapt to constrained environments and mitigate damage due to impact. Given these features, jumping has been explored as a mode of locomotion for soft robots. However, for mesoscale jumping robots, lightweight and compact actuation are required. Previous work focused on systems powered by fluids, combustion, smart materials, electromagnetic, or electrostatic motors, which require one or more of the following: large rigid components, external power supplies, components of specific, pre-defined sizes, or fast actuation. In this work, we propose an approach to design and fabricate an electrically powered soft amplification mechanism to enable untethered mesoscale systems with continuously tunable performance. We used the tunable geometry of a liquid crystal elastomer actuator, an elastic hemispherical shell, and a pouch motor for active latching to achieve rapid motions for jumping despite the slow contraction rate of the actuator. Our system amplified the power output of the LCE actuator by a factor of 8.12 × 103 with a specific power of 26.4 W/kg and jumped to a height of 55.6 mm (with a 20 g payload). This work enables future explorations for electrically untethered soft systems capable of rapid motions (e.g., jumping).

Tuning the Morphology of Suction Discs to Enable Directional Adhesion for Locomotion in Wet Environments.

Reversible adhesion provides robotic systems with unique capabilities, including wall climbing and walking underwater, and yet the control of adhesion continues to pose a challenge. Directional adhesives have begun to address this limitation by providing adhesion when loaded in one direction and releasing easily when loaded in the opposite direction. However, previous work has focused on directional adhesives for dry environments. In this work, we sought to address this need for directional adhesives for use in a wet environment by tuning the morphology of suction discs to achieve anisotropic adhesion. We developed a suction disc that exhibited significant directional preference in attachment and detachment without requiring active control. The suction discs exhibited morphological computation-that is, they were programmed based on their geometry and material properties to detach under specific angles of loading. We investigated two design parameters-disc symmetry and slits within the disc margin-as mechanisms to yield anisotropic adhesion, and through experimental characterizations, we determined that an asymmetric suction disc most consistently provided directional adhesion. We performed a parametric sweep of material stiffness to optimize for directional adhesion and found that the material composition of the suction disc demonstrated the ability to override the effect of body asymmetry on achieving anisotropic adhesion. We modeled the stress distributions within the different suction disc symmetries using finite element analysis, yielding insights into the differences in contact pressures between the variants. We experimentally demonstrated the utility of the suction discs in a simulated walking gait using linear actuators as one potential application of the directional suction disc.

Variable Stiffness Devices Using Fiber Jamming for Application in Soft Robotics and Wearable Haptics.

Variable stiffness actuation has applications in a wide range of fields, including wearable haptics, soft robots, and minimally invasive surgical devices. There have been numerous design approaches to control and tune stiffness and rigidity; however, most have relatively low specific load-carrying capacities (especially for flexural loads) in the most rigid state that restricts their use in small or slender devices. In this article, we present an approach to the design of slender, high flexural stiffness modules based on the principle of fiber jamming. The proposed fiber jamming modules (FJMs) consist of axially packed fibers in an airtight envelope that transition from a flexible to a rigid beam when a vacuum is created inside the envelope. This FJM can provide the flexural stiffness of up to eight times that of a particle jamming module in the rigid state. Unlike layer jamming modules, the design of FJMs further allows them to control stiffness while bending in space. We present an analytical model to guide the parameter choices for the design of fiber jamming devices. Finally, we demonstrate applications of FJMs, including as a versatile tool, as part of a kinesthetic force feedback haptic glove and as a programmable structure.

Electronics-free pneumatic circuits for controlling soft-legged robots.

Pneumatically actuated soft robots have recently shown promise for their ability to adapt to their environment. Previously, these robots have been controlled with electromechanical components, such as valves and pumps, that are typically bulky and expensive. Here, we present an approach for controlling the gaits of soft-legged robots using simple pneumatic circuits without any electronic components. This approach produces locomotive gaits using ring oscillators composed of soft valves that generate oscillating signals analogous to biological central pattern generator neural circuits, which are acted upon by pneumatic logic components in response to sensor inputs. Our robot requires only a constant source of pressurized air to power both control and actuation systems. We demonstrate this approach by designing pneumatic control circuits to generate walking gaits for a soft-legged quadruped with three degrees of freedom per leg and to switch between gaits to control the direction of locomotion. In experiments, we controlled a basic walking gait using only three pneumatic memory elements (valves). With two oscillator circuits (seven valves), we were able to improve locomotion speed by 270%. Furthermore, with a pneumatic memory element we designed to mimic a double-pole double-throw switch, we demonstrated a control circuit that allowed the robot to select between gaits for omnidirectional locomotion and to respond to sensor input. This work represents a step toward fully autonomous, electronics-free walking robots for applications including low-cost robotics for entertainment and systems for operation in environments where electronics may not be suitable.

Reversible adhesion to rough surfaces both in and out of water, inspired by the clingfish suction disc.

Adhesion is difficult to achieve on rough surfaces both in air and underwater. In nature, the northern clingfish (Gobiesox maeandricus) has evolved the impressive ability to adhere onto substrates of various shapes and roughnesses, while subject to strong intertidal surges. The suction disc of the clingfish relies on suction and friction to achieve and maintain adhesion. Inspired by this mechanism of attachment, we designed an artificial suction disc and evaluated its adhesive stress on rough surfaces and non-planar geometries. The artificial suction disc achieved adhesion strengths of 10.1 ± 0.3 kPa in air on surfaces of moderate roughness (grain size, 68 µm), and 14.3 ± 1.5 kPa underwater on coarse surfaces (grain size, 269 µm). By comparison, a commercially available suction cup failed to exhibit any significant adhesion in both scenarios. The roughly 2 g heavy clingfish-inspired suction discs gripped concave surfaces with small radii of curvature (12.5 mm) and supported payloads up to 0.7 kg. We correlated the effect of key bioinspired features (i.e. slits, a soft outer layer, and body geometry) to adhesion performance using contact visualization techniques and finite element analysis (FEA). The suction discs were then tested on a remotely operated vehicle (ROV) to demonstrate their utility in the soft manipulation of fragile objects.

Jellyfish-Inspired Soft Robot Driven by Fluid Electrode Dielectric Organic Robotic Actuators.

Robots for underwater exploration are typically comprised of rigid materials and driven by propellers or jet thrusters, which consume a significant amount of power. Large power consumption necessitates a sizeable battery, which limits the ability to design a small robot. Propellers and jet thrusters generate considerable noise and vibration, which is counterproductive when studying acoustic signals or studying timid species. Bioinspired soft robots provide an approach for underwater exploration in which the robots are comprised of compliant materials that can better adapt to uncertain environments and take advantage of design elements that have been optimized in nature. In previous work, we demonstrated that frameless DEAs could use fluid electrodes to apply a voltage to the film and that effective locomotion in an eel-inspired robot could be achieved without the need for a rigid frame. However, the robot required an off-board power supply and a non-trivial control signal to achieve propulsion. To develop an untethered soft swimming robot powered by DEAs, we drew inspiration from the jellyfish and attached a ring of frameless DEAs to an inextensible layer to generate a unimorph structure that curves toward the passive side to generate power stroke, and efficiently recovers the original configuration as the robot coasts. This swimming strategy simplified the control system and allowed us to develop a soft robot capable of untethered swimming at an average speed of 3.2 mm/s and a cost of transport of 35. This work demonstrates the feasibility of using DEAs with fluid electrodes for low power, silent operation in underwater environments.

Comparative Docking Studies: A Drug Design Tool for Some Pyrazine- Thiazolidinone Based Derivatives for Anti-HIV Activity.

BACKGROUND: Acquired immunodeficiency Syndrome (AIDS) is caused by Human immunodeficiency virus type 1 (HIV-1). Pyrazine and Thiazolidinone pharmacophore has diverse biological activities including anti HIV activity. AIMS AND OBJECTIVES: To study binding behavior of Pyrazine- thiazolidinone derivatives on four different crystal structures of HIV- 1RT.These molecules which were already reported as anti-TB were investigated for dual activity as Anti-HIV and Anti-TB. MATERIALS AND METHODS: In the present study we describe a comparative docking study of twentythree derivatives of N-(4-oxo-2 substituted thiazolidin-3-yl) pyrazine-2-carbohydrazide. Binding pattern of these derivatives was gauged by molecular docking studies on four different receptors bearing PDB code 1ZD1, 1RT2, 1FKP and 1FK9 of HIV-RT enzyme using V. Life MDS software Genetic algorithm docking method. RESULT AND DISCUSSION: The studies revealed hydrogen bonds, hydrophobic interaction and pi-pi interactions playing significant role in binding of the molecules to the enzyme. CONCLUSION: Most of the molecules have shown good dock score and binding energy with anti-HIV receptors but Molecules 13 and 14 have potential to act as anti-tubercular and Anti HIV and hence can be further explored for dual activity.