The Nov. 16 issue of Science has a special section on Robotics. I thought this graphic from the article by Pfeifer et al. - "Self-Organization, Embodiment, and Biologically Inspired Robotics" - was fascinating. It describes several biologically inspired robots.
Figure: Self-organization, dynamics, and materials in bio-inspired robotics. (A) Smooth transition between swimming and walking. This amphibious salamanderlike robot (~80 cm long) embeds a spinal cord model that explains the ability of salamanders to switch between swimming and walking. The locomotion model is built by extending a primitive neural circuit for swimming by phylogenetically more recent limb oscillatory centers. (B) Rich sensory stimulation through proper sensor morphology. This robot (~7 cm in diameter) owes its sophisticated sensory capacities to the specific arrangement, shape, and material characteristics of its whiskers. Natural whiskers from rodents (such as the ones used on this robot) are far superior to whiskers built from other materials in terms of richness of the signals relayed to the neural system. (C) Self-stabilizing rapid hexapod locomotion. This robot (~15 cm long) moves with a bouncing gait, achieving rapid (over 4 body lengths per second) locomotion. Its legs are built with compliant pneumatic actuators, which yield self-stabilization through mechanical feedback. (D) Passive dynamics–based walking. Designed to work on a slope as a dynamic walker, this robot (~45 cm tall) exploits dynamics and morphology (in particular, the shape and length of the body and feet) to achieve stable walking. The robot's natural dynamics serves as the target dynamics for a reinforcement learning mechanism, enabling the robot to quickly learn to walk on flat ground. (E) Self-stabilizing vertical takeoff through materials and morphology. Inspired by flies, this ultralight (60 mg, 3-cm wingspan) ornithopter (a device that flies by flapping its wings) generates sufficient lift to take off vertically (power is supplied externally). A large part of the control is delegated to the morphological and material properties of the robot. Compliant structures are driven into resonance to produce a large wing stroke, and flexible material is used in the wing hinges to allow for passive rotations of the wings. (F) Agile wall-climbing through materials. The bio-inspiration for this palm-sized robot is provided by the gecko and its uncanny climbing talents. The robot's tri-foot (three-footed wheel) is equipped with a polymer dry adhesive material, which to some extent has contact properties comparable to those of its biological analog. The robot can flexibly navigate on smooth vertical and even inverted surfaces. (G) Morphing through localized self-reconfiguration. This self-reconfigurable robot is composed of active (actuated, black) and passive (nonactuated, white) cubic modules (~400 g, ~60 to 65 mm side length). The modules connect to each other through hooks, which enables the robot to change its morphology in a large number of ways. The picture shows the metamorphosis from a four-legged (quadruped) structure to a linear (snakelike) structure. (H) Global movement through local interaction dynamics. The individual wheel-like modules (~10 cm in diameter) constituting this robot are equipped with spokelike parts driven by linear actuators. The wheels lie horizontally on the ground and attach to neighboring modules by Velcro. Although no module can move on its own, by using neural oscillators as drivers for the actuators and through the physical coupling between the units, a coordinated global wave of activation can be induced in clusters of more than 30 modules, which leads to forward movement, even though there is no global control.