Magnetic resonance imaging is an inherently signal-to-noise-starved technique that limits the spatial resolution, diagnostic image quality and results in typically long acquisition times that are prone to motion artefacts. This limitation is exacerbated when receive coils have poor fit due to lack of flexibility or need for padding for patient comfort. Here, we report a new approach that uses printing for fabricating receive coils. Our approach enables highly flexible, extremely lightweight conforming devices. We show that these devices exhibit similar to higher signal-to-noise ratio than conventional ones, in clinical scenarios when coils could be displaced more than 18 mm away from the body. In addition, we provide detailed material properties and components performance analysis. Prototype arrays are incorporated within infant blankets for in vivo studies. This work presents the first fully functional, printed coils for 1.5- and 3-T clinical scanners.
Multiple sensors can be used on a mobile robot so that it can perceive its environment with better accuracy than if either sensor were used alone. Sonar and infrared sensors are used here in a complementary fashion, where the advantages of one compensate for the disadvantages of the other. The robot then combines the information from the two sensors to build a more accurate map. Another representation, a modified version of the curvature primal sketch, is extracted from this perceived workspace and is used as the input to two path planning programs: one based on configuration space and one based on a generalized cone formulation of free space.
We have demonstrated an autonomous two-legged microrobot which has taken its first steps. The body of the robot is fabricated in a planarized silicon-on-insulator (SOI), two-layer polysilicon process and is 8.5 mm x 4 mm x 0.5 mm in size. We previously reported initial leg motion from an off-board controller but have now incorporated control and power supplies onto the robot, resulting in autonomous operation for the first time. This solar-powered microrobot has two, one degree-offreedom (DOF) legs and drags its tail end. Leg motion is generated via electrostatic inchworm motors on the robot body. The robot is a three chip hybrid assembled from one chip which contains the robot's motors and legs, a second chip which integrates both solar cells and high voltage buffers, and a third chip which incorporates CMOS circuitry for sequencing the legs. The robot has demonstrated 3 mm of motion shuffling sideways and has lifted its front end more than 300 µm above the surface. The total weight of the three-chip robot is only 10.2 mg.
This work investigates fundamental limits on electromechanical energy conversion capacity of piezoelectric transformers by considering a work cycle analysis. Fundamental limitations in a lossless piezoelectric transformer are imposed by maximum electric field strength, maximum surface charge density, maximum stress, and maximum strain. For the lossless case, our analysis indicates that the mechanical stress limit is the effective constraint in typical PZT materials. For a specific PZT-5H sample considered, a mechanical stress-limited work cycle indicates that this material can handle 330 W/cm 3 at 100 kHz.A second direction this work has taken has been an investigation into a soft-switching drive and control circuit, that does not require any magnetic components. The theory of operation of softswitching resonant drive circuitry is discussed, and experimental results on a soft-switching inverter incorporating no magnetic components are reported.
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