In this paper, we report on a system for the management of diabetes using jet injection. Jet injection uses a high-speed liquid jet to break the surface of the skin without requiring a needle. We propose that a single jet injection system may be capable of performing the key steps of insulin therapy including releasing and collecting blood, measuring blood glucose concentration, and administering insulin. We have previously demonstrated that our system can penetrate fingertip skin with a small (~20 µL) jet injection. In this work we present a secondary piston to maintain a partial vacuum pressure of −40 kPa by reversing the injector. The application of this partial vacuum is essential to enhance the volume of blood release to ensure sufficient blood is collected for a glucose measurement. On a silicone model of a hand, we demonstrate that the system can automatically extract and transfer blood into a glucose test strip. This is achieved using a device that retains the ability to then deliver subcutaneous jet injections of up to 300 µL of insulin.

Soft materials and compliant actuation concepts have generated new design and control approaches in areas from robotics to wearable devices. Despite the potential of soft robotic systems, most designs currently use hard pumps, valves, and electromagnetic actuators. In this work, we take a step towards fully soft robots by developing a new compliant electromagnetic actuator architecture using gallium-indium liquid metal conductors, as well as compliant permanent magnetic and compliant iron composites. Properties of the new materials are first characterized and then co-fabricated to create an exemplary biologically-inspired soft actuator with pulsing or grasping motions, similar to Xenia soft corals. As current is applied to the liquid metal coil, the compliant permanent magnetic tips on passive silicone arms are attracted or repelled. The dynamics of the robotic actuator are characterized using stochastic system identification techniques and then operated at the resonant frequency of 7 Hz to generate high-stroke (>6 mm) motions.

We present the conceptual design for a single degree-of-freedom shoulder assistive robot powered by a direct-drive linear electric motor. Such actuators offer high bandwidth and inherent force transparency, advantageous properties for an assistive device, but traditionally have inadequate force densities. We develop a model to describe the interaction between the robot kinematics and the actuator performance, and find the optimal actuator configuration. We also demonstrate the ability of a single design of such a device to fit a wide range of patients, and determine indicative power and mass specifications for the actuator. The resulting power and mass levels of approximately 1 kg and 130 W are well within the feasible range for a wearable device.

We present the design of a novel direct-drive linear permanent magnet synchronous motor with a high continuous-duty force-to-mass ratio. We use an analytical electromagnetic model to find optimal dimensions for a new magnet configuration, comprising nested tubular Halbach arrays. We further use the analytical model to map out the design space for these motors, and investigate possible designs for motors with muscle-like force production. We then describe the design of a 100 g-scale motor based on the optimization, with water cooling and a lightweight structure. Experimental results suggest that this motor is capable of over 140 N/kg continuous force production, and demonstrate that it can be used for positioning at over 1 m/s and with 40 g acceleration unloaded.

Conducting polymer actuators such as polypyrrole can generate stresses over 10 times larger than skeletal muscle and have typical repeatable strains between 1% and 12%, making them potential candidates for lightweight, low-cost, robotic applications. Polypyrrole linear actuators under closed loop control have not been previously reported. Here we report the open and closed loop performance of polypyrrole linear contractile actuators evaluated at pre-loaded stresses of 1 MPa to 3 MPa. A standard PI control scheme driving a potentiostat was implemented in conjunction with positioning feedback from a DC/DC linear variable differential transformer (LVDT). A dynamic positioning range of 3400 is reported, with a positioning resolution of 125 nm (0.001% strain) and a maximum repeatable displacement of 427 microns (3.6% strain). The open loop frequency response of actuator strain shows characteristics of a first-order low pass filter with a log gain versus log frequency slope near -1 for frequencies tested between 0.05 Hz to 2 Hz. The closed loop frequency response of actuator strain when tracking a sinusoidal set-point signal of 0.5% strain shows characteristics of a first order system with one zero, with a corner frequency near 0.08 Hz and an operating bandwidth up to 1 Hz. Step responses at various controller output maximum voltages show a reduction in contractile response times by a factor of four, where higher voltages yield faster contractile responses.