The goal of this research is to make possible the accurate mapping of the high-frequency dielectric (or impedance) properties of materials ranging from device wafers and polymeric substrates (in-line process control) to biological materials, such as human skin, at multiple depths on a fine scale. The conductive coaxial needles will be configured on a fixed-grid array and be of lengths varying from ~50-250 microns. The resulting constructs also provide a new technology to affordably produce RF probes with small separations. The reduction of probe costs (from few thousand dollars per probe to few dollars per probe) has the potential to transform RF-test protocols and enable affordable wafer level probing at a fine scale. Local integration of the electronics provides a low-noise measurement solution, but requires significant miniaturization and therefore motivates a transmission line approach with minimum leakage and cross-talk. Intellectual Merit - Existing methods for high-frequency material characterization will be refined in scale and sample density by the proposed microsystem. Unlike current techniques that provide single point measurement in the range of 100's of microns, the proposed MEMS-based approach will enable a large number of measurements (while enabling multi-point sampling via the fixed needle matrix). This research represents a new merging of MEMS and microwave-suitable sensing techniques for impedance measurements. Broader Impacts - The technology addressed in this research will impact several areas of test, measurement and systems design ranging from materials characterization to detection of impurities in wafer scale processing. The probe architectures will be suitable for high frequency metrological characterization of micron-scale devices, such as emerging mm- and sub-mm-wave transistor technologies. The fabrication techniques for producing integrated micro coaxial transmission lines will facilitate the development of 3-D microwave and mm-wave systems for sensing and communications, while simultaneously integrating sensing and packaging functions of the material. Finally, the ability for fine-scale material characterization will aid research in many materials-related areas including nano-particle thin-films, lubricants, fuels and other fluids. The research provides new opportunities for research fellows in our active training programs (Bridge to Doctorate and Alfred P. Sloan Foundation Doctoral Fellowship Program). The research outcomes will also be integrated into a new graduate level sequence at the University of South Florida that forms the core curriculum for our training grants.