NMR-microprobes based on solenoids and Helmholtz coils have been microfabricated and NMR-spectra of mammalian cells have successfully been taken. The microfabrication technology developed for these probes consists of three electroplated copper levels for low resistance coils and three SU-8 layers for the integration of microchannels. This technology allows fabricating solenoids, Helmholtz and planar coils on the same wafer. The coils have inner diameters in the range of 160 to 400 microm and detection volumes of 5 to 22 nL. The solenoid and Helmholtz coils show improved RF-field characteristics compared to a planar coil fabricated with the same process. The fabricated solenoid has a particularly low resistance of only 0.46 Omega at 300 MHz. Moreover, it is very sensitive and has a very uniform RF-field, but shows large line width. The Helmholtz coils are slightly less sensitive, but display a far narrower line width, and are therefore a good compromise. With a Helmholtz coil, a SNR of 620 has been measured after one scan on 9 nL pure water. An NMR-microprobe based on a Helmholtz coil has also been used to take spectra of CHO cells that have been concentrated in the sensitive region of the coil with a mechanical filter integrated into the channel.
An Ultra-Low-Power readout architecture for capacitive MEMS-based accelerometers and strain sensors is presented. The system can read both accelerometers and strain sensors in a half-bridge configuration. An accurate VerilogA model of the sensor was made to improve simulations. The gain of the system is controlled by integrating pulses from the excitation circuit allowing accurate control of the Signal-to-Noise ratio. A Figure-of-Merit of 4.41 × 10 −20 F √ (W/Hz) was achieved for a sensor range of ±2.0 g and ±20,000 over a 100 Hz bandwidth. A minimum of 440 nW power consumption was recorded. Residual motion artifacts are also cancelled by the system.
An Ultra-Low-Power readout architecture for capacitive MEMS-based accelerometers and strain sensors is presented. The system can read both accelerometers and strain sensors in a half-bridge configuration. An accurate VerilogA model of the sensor was made to improve simulations. The gain of the system is controlled by integrating pulses from the excitation circuit allowing accurate control of the Signal-to-Noise ratio. A Figure-of-Merit of 4.41 × 10 −20 F √ (W/Hz) was achieved for a sensor range of ±2.0 g and ±20,000 over a 100 Hz bandwidth. A minimum of 440 nW power consumption was recorded. Residual motion artifacts are also cancelled by the system.
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