Abstract-Recent biological studies on water strider insects revealed the detailed mechanism of their staying and walking on water. While macro scale bodies use buoyancy to stay on water, these very light and small insects balance their weight using repulsive surface tension forces where the insect legs are covered with hydrophobic micro-hairs. Utilizing the unique scaling advantage of these insects, this paper proposes a biologically inspired miniature micro-robot walking on water with a similar principle. The paper focuses on understanding physical characteristics of the insect and designing a robot that mimics the insect's movement. Highly hydrophobic Teflon ® coated wires are used for the legs to take advantage of surface tension force, and the robot body is made of carbon fibers for minimal weight. A T-shaped actuation mechanism with three PZT-5H based unimorph actuators is utilized to move the side legs of the robot independently for controlled locomotion. Kinematics and dynamic properties of the robot prototype are analyzed and compared with the experimental results. The tethered robot can successfully move forward, backward and can also make turns. Maximum speed of the robot in forward motion is 2.3 cm/s. In the future, environmental monitoring applications on dams, lakes, sea, etc. would become possible using a network of these robots with miniature sensors, an on-board power source and electronics.

Abstract-Conventional pneumatic actuators have been a popular choice due to their decent force/torque output. Nowadays, new generation of pneumatic actuator made out of highly compliant elastomers, which we call soft pneumatic actuators (SPA), are drawing increasing attention due to their ease of fabrication, high customizability and innately softness. However, there is no effective method presented to characterize and understand these actuators, such as to measure the force and torque output, range of motion and the speed of actuation.In this work, we present two types of SPAs: bending and rotary actuators. In addition, we have developed two measurement setups to characterize actuators of different geometries. The measured force/torque outputs of different actuators are presented and analyzed.Step responses to certain pressure input are presented and discussed. A simple model is presented to provide physical insight to the observed behavior of the soft actuators. This work provides the basis for designing customized SPAs with application-specific requirements.

Recently, a few water strider robots that mimic the static and dynamic key characteristics of the insect water striders have been reported in the literature. These robots either lacked mobility or was tethered to an external source of power. Using the recent findings on the supporting legs of these robots creating repulsive surface tension based lift forces, a heavier yet highly maneuverable and non-tethered water strider robot, called STRIDE, is proposed in this paper. STRIDE uses two miniature DC motors and a lithium-polymer battery that are connected to the driving circuit on-board. Optimal leg shape is manufactured by bending 0.33 mm diameter stainless steel wires with a Teflon R coating. This 6.13 gr non-tethered robot with twelve supporting legs demonstrated a linear motion of 8.7 cm/s and a rotational motion of 0.8 rad/s. STRIDE would have potential applications in continuous water quality monitoring on lakes, dams, and other water sources and in entertainment and education in the near future.

No abstract