This Small Business Innovative Research (SBIR) Phase-I project will develop micro-electro-mechanical-systems (MEMS) comprised of engineered magneto-electric (ME) materials to enable wireless power transfer systems for medical implants. Engineered ME materials are composites of magnetostrictive (M) and electro-active (E) components that convert magnetic fields into voltages much more efficiently than do natural MEs. Incumbent wireless power technologies rely on coils to convert time-dependent magnetic fields, generally at radio frequencies, into useful power. Bulk ME receivers, though not yet optimized, show increasing sensitivity advantages over comparable-size, high-permeability coil receivers as frequency and/or device size decreases. A series of several dozen generic MEMS resonators (cantilevers, bridges, plates in different sizes and aspect ratios) were designed with high-Q, epitaxial piezoelectric films grown on single-crystal substrates. Phase I of the new program includes characterizing the mechanical integrity and resonance characteristics of the piezoelectric MEMS substrates. Photo-resist masks for selected devices will be designed to allow deposition of M films on the piezoelectric resonators to create generic ME-MEMS devices. These devices will be packaged and tested for received power-per-unit-magnetic-field at different frequencies and field strengths. Data will be analyzed and compared with that for bulk ME and coil devices.
The broader impact/commercial potential of this project should extend well beyond development of smaller and more efficient wireless power systems for implanted medical devices. High-performance ME wireless power receivers have not yet been made at the MEMS scale. This research program will develop new thin film processing techniques for deposition of high Q amorphous magnetic films and CMOS-compatible, piezoelectric films on each other that would impact many technical markets including magnetic and/or acoustic sensors, communications systems capable of operation in environments that hinder conventional radio transmission, and possibly new multifunctional components for intelligent electronic systems. Successful development of ME-MEMS receivers will enable a variety of engineered ME devices, such as: i) magnetometers that could rival SQUID magnetometers in sensitivity while consuming far less power and operating at room temperature rather than L-He temperatures, ii) systems for low-frequency communications in high-absorption environments where RF systems fail; iii) advanced processes for co-deposition of magnetic and electro-active films, enabling new applications of multi-functional ME-MEMS devices.
" NSF 10-607 AM 7 Smart and Specialized Materials R. C. Oâ€™Handley, PI, Jiankang Huang, President Ferro Solutions, Inc.., 5 Constitution Way, Woburn MA 01801 Aim: Present techniques for powering implanted devices are based on either magnetic induction, acoustic transmission or finite-life storage cells. This Ferro Solutions (FS) Phase I project began with the insight that when induction-coil-based devices operate at lower frequency and/or are made at smaller sizes, they become increasingly less effective at generating a voltage or wireless power from an alternating magnetic field. In contrast, engineered magneto-electric (ME) devices have shown evidence of performing better than coils under these conditions and MEs are also better suited to micro-fabrication . As wireless power is needed for more applications involving small implantable devices, incumbent technologies could be replaced increasingly by ME devices. Method. To take the first steps in quantitatively defining this paradigm shift in wireless power, we proposed a program of micro-fabrication and testing of a series of generic micro-electro-mechanical systems (MEMS)-ME test structures resonators (single and double cantilever beams and other resonant structures, each with electro-active and magnetic layers as well as a variety of electrode configurations). The fabricated devices were cut to die, each 2.3 mm square and typically containing about 20 different resonators. Selected die were bonded to substrates to which wire bonding of each device could be made for characterization. Resonator displacement in alternating magnetic field (1 Oe peak) was measured with a laser vibrometer. The stress on the electro-active layer, subsequent voltage across different electrode configurations and output power were calculated from cantilever tip displacement using a proprietary MEMS-ME model developed during the program. Power density results were compared with the performance of induction coils and Li-ion storage cells. 1a. Intellectual Merit. We believe our MEMS-ME devices to be the first ever successfully fabricated and tested. Novel micro-fabrication techniques had to be developed, including improved sputtering conditions for the magnetic layer deposited on the piezoelectric resonators. A detailed phenomenological model based on conservation of magnetic, piezoelectric and elastic energy as well as loss, was developed to enable detailed analysis of the measured ME resonator displacement. Analysis confirmed our earlier measurements and estimates that ME wireless receivers can outperform coils below a size scale of a few mm . Also ME devices appear to last longer than Li-ion batteries of equal volume under loads typical of implanted medical devices. 1b. Broad impact. The immediate area of application for MEMS-ME wireless power receivers is medical implants for health monitoring, diagnosis, drug delivery and other therapies where coils would not work or batteries would fail before the intended duration of the medical intervention. Ultimately MEMS-MEs could provede power for sensor or control networks deployed in inaccessible places, all0wing costly wiri installation to be dispensed with. 2. Publications and other products. A major publication is in preparation describing the improved MEMS-ME model and its predictions. A more detailed technical report will follow for use internally, with our subcontractors and possible future licensing. 3. Additional. A Phase II proposal has been submitted to NIH that could lead to the use of MEMS-ME devices to deliver power and exchange data wirelessly to mice and other small animal medical test subjects. [1 ] "Improved Wireless, Transcutaneous Power Transmission for In Vivo Applications", R.C. Oâ€™Handley, J K Huang, D.C. Bono, and J. Simon, IEEE Sensors Journal, 8 (1), 57-62, (2008).