A novel robotic sensor is proposed to measure both the contact angle and the force acting between the tip of a surgical robot and soft tissue. The sensor is manufactured using a planar lithography process that generates microchannels that are subsequently filled with a conductive liquid. The planar geometry is then molded onto a hemispherical plastic scaffolding in a geometric configuration enabling estimation of the contact angle (angle between robot tip tangent and tissue surface normal) by the rotation of the sensor around its roll axis. Contact force can also be estimated by monitoring the changes in resistance in each microchannel. Bench top experimental results indicate that, on average, the sensor can estimate the angle of contact to within ±2° and the contact force to within ±5.3 g.

A novel robotic tool is proposed to enable the surgical removal of tissue from inside the beating heart. The tool is manufactured using a unique metal MEMS process that provides the means to fabricate fully assembled devices that incorporate micron-scale features in a millimeter scale tool. The tool is integrated with a steerable curved concentric tube robot that can enter the heart through the vasculature. Incorporating both irrigation and aspiration, the tissue removal system is capable of extracting substantial amounts of tissue under teleoperated control by first morselizing it and then transporting the debris out of the heart through the lumen of the robot. Tool design and robotic integration are described and ex vivo experimental results are presented.

An active flexural hinge has been developed and incorporated into the transmission of a prototype flapping-wing robot. The multilayered flexure, which is constructed from a shape memory polymer and a polyimide film, showed controllable stiffness under change in temperature. At room temperature, the flexure had a bending stiffness of 572 mN·mm; when warmed to 70°C, the stiffness was 11 mN·mm. The resulting single-wing flapping system demonstrated up to an 80% change in generated lift without modification of the waveform of the main driving piezoelectric actuator. Such active stiffness tunable flexure joints could be applied to any flexural miniature mobile robot and device mechanisms.

Flapping-flight micro aerial vehicles (MAVs) pose an ongoing design problem to the scientific community, requiring careful consideration of both body structure and force production. Here, we examine a flapping MAV prototype with a passively rotating wing design. While at the current scale the lift force produced is not enough for liftoff, observing its performance under roll and pitch control can lead to insights on both the body design and the eventual free-flight implementation. As the production of roll and pitch torques are primarily uncoupled for this design, PID control is implemented in the roll and pitch directions individually on a custom designed single degree of freedom rig. By doing so, we show that the body structure is capable of sustaining independent wing amplitudes and that actuator input voltage bias shifting is successful experimentally on a dynamically driven wing. Through force compensation, the experimentally tested controller is mapped to a 1/2 scale simulated system, theoretically capable of free-flight. Though initial simulation results suggest high sensitivity to feedback noise, simulations show that decoupled roll and pitch controllers have potential as a minimal computational means for hovering and translational motion.

In this work we develop a stochastic dynamic model of bacteria propelled spherical micro-robots. S. marcescens type bacteria attach in small numbers to the surfaces of spherical microbeads. Given a small number of attached bacteria, generally 8-41, collective-behavior stochastic models become not applicable, hence a model based on individual bacterium behavior and motion is developed. This stochastic simulation is used to study the flexibility of the flagellar hook by comparing simulated and experimental results. The effect of bead diameter and the number of attached bacteria is investigated in this manner, with the results favoring a stiffer flagellar hook. The theoretical framework is intended to be used as a simulation and design tool for bacteria propelled micro-robots employed in future medical applications.

Flapping wing micro-aerial vehicles (MAVs) hold great potential for matching the agility of flies, their source of inspiration. At small scales, however, it becomes difficult to balance design mechanical complexity and the weight/lift ratio. Considering control in the initial stages of vehicle design can help define system feasibility and the consequences of making design simplifications. Here, four design alternatives based on a piezoelectric driven passive pitch reversal wing are modeled and compared based on their performance under an ideal linear quadratic regulator (LQR) control scheme. State error over straight line, circular, and cube trajectories are used as a means of comparison. Wing lift and reasonable control input bounds are defined for each design variation. While not nearly as maneuverable as flies, these designs show promise as feasible controllable vehicles.

One of many difficulties in creating flapping wing miniature robotic aerial vehicles lies in generating proper wing trajectory that would result in sufficient lift forces for hovering and maneuvering. A completely passive wing pitch reversal design based on the wingpsilas inertial dynamics is proposed. Dynamics are simulated using a Lagrangian formulation, resulting in theoretical predictions for aerodynamic forces and motion trajectory. Based on the generated wing lift and rotation trajectory delay, the wingpsilas sensitivity to variations in spring stiffness, damping coefficient, driving frequency, and rotation axis position is analyzed and the above parameters are evaluated for efficiency as control inputs. Furthermore, a wing control methodology based on slow actuation of spring stiffness and flapping frequency is proposed, allowing for partial position/orientation of the robot in free space.