We report the design of a two-degree-of-freedom microelectromechanical systems nanopositioner for on-chip atomic force microscopy (AFM). The device is fabricated using a silicon-on-insulator-based process to function as the scanning stage of a miniaturized AFM. It is a highly resonant system with its lateral resonance frequency at ∼850 Hz. The incorporated electrostatic actuators achieve a travel range of 16 µm in each direction. Lateral displacements of the scan table are measured using a pair of electrothermal position sensors. These sensors are used, together with a positive position feedback controller, in a feedback loop, to damp the highly resonant dynamics of the stage. The feedback controlled nanopositioner is used, successfully, to generate high-quality AFM images at scan rates as fast as 100 Hz.[2013-0063]

None-invasive blood glucose measurement enables effective diagnosis and treatment of diabetic patients. The existing microwave sensors suffer from low sensitivity and large size. This article presents a highly sensitive and compact size non-invasive microwave sensor for real-time blood glucose measurements. We have developed a new sensing technique using directly connected Branch Line Coupler and Split Ring Resonators. This technique significantly improves the sensitivity by mitigating the limited coupling between transmission lines and resonators. In addition, using Split Ring Resonators reduces the sensor size due to capacitive and inductive effects, which are loaded to the Branch Line Coupler. The proposed sensing function is based on shifting the transmission notch frequency in coupled arm of the Branch Line Coupler, which is caused by loading the Split Ring Resonators with varying glucose concentration. A prototype sensor is fabricated and successfully tested using several glucose concentrations in deionized water. Experimental results demonstrate 0.72 MHz/mgdL -1 measurement sensitivity, which is higher in comparison with available sensors in PCB technology. The prototype sensor size is 3.5×3.5×0.16 cm 3 .

A novel dual band, highly sensitive Substrate Integrated Waveguide (SIW) sensor for permittivity measurements is presented. A pair of modified Complementary Split Ring Resonators (CSRRs) is etched on SIW surface. CSRRs are located in the center of SIW, where the electric field distribution is high so that the coupling be maximized. The coupling between the SIW and the CSRRs as well as the adjacent CSRRs results in two notches in transmission coefficient. These notches vary with the dielectric loading on the sensor. The ratio of notch variation to the load permittivity variation determines the sensitivity of proposed sensor. Two sensitivities proportional to two notches are provided. Normalized sensitivities from both notches show identical values. Therefore, any environmental effect have the same impact on the TZs. This demonstrates the potential of the proposed sensor for differential operation that can mitigate the effect of environmental conditions. The size of the proposed sensor is small as the inductive and the capacitive effects of CSRRs forced the SIW to operate below the cut off frequency at negativeorder-resonance mode. All design steps including SIW design, CSRRs design and modified CSRRs effects are presented in details. The sensor operation principle is described through its equivalent circuit model and simulation results. The experimental results indicates that the normalized sensitivity is 3.4%, which is much higher than similar sensors. The prototype sensor size (27.8×18.4×0.508 mm 3 ) is smaller than those reported in the literature.

The microwave sensors have been successfully used for permittivity measurement. These sensors suffer from limited sensitivity and environmental effects. This paper presents a novel T-junction highly sensitive microwave sensor for permittivity measurement of low loss solid materials. The proposed sensor operation principle is based on downshifting the transmission zero of the outputs of T-junction with the coupling of the material under test (MUT). The sensing section consist of an interdigital capacitor (IDC) located in between the lines of the T-junction. IDC is directly connected to output arms of T-junction so that it could disturb the outputs strongly. Any change in electric field concentration in IDC directly is transmitted to the outputs and is translated as TZ change. Design steps including T-junction and IDC effects on outputs are presented in details. The sensor operation principle is described through an equivalent circuit model which is validated by simulation and experimental results. Two outputs of the proposed sensor show the same electrical performances which allow differential operation mode. Hence, cross sensitivity due to environmental factors can be tolerated by the sensor. Measurement results of the fabricated prototype shows 𝟏𝟏𝟐 𝑴𝑯𝒛 frequency shift per unit permittivity change, and a normalized sensitivity of 3.9 %, which are larger than available similar sensors. The proposed sensor is implemented on a 𝟐𝟐. 𝟐𝟐 × 𝟏𝟖. 𝟕𝟔 × 𝟏. 𝟔 𝒎𝒎 𝟑 printed circuit board.

Abstract-Frequency modulation technique can be applied to microelectromechanical systems (MEMS) transducers that require some form of resistive sensing. For example, electrothermal sensing is being investigated as a viable means of measuring displacement in micromachined transducers. This paper proposes a highly sensitive readout circuit, which can convert 10 change of resistance in a 400 electrothermal sensor to more than 200 kHz frequency variation (350-550 KHz). The frequency variations are then converted to voltage values by means of a frequency demodulation. In addition, the proposed technique achieves high linearity from the voltage applied to the actuator to the voltage measured at the sensor's output, which can potentially eliminate the need for an additional linearization if the sensor is used in a feedback loop. The proposed approach leads to high sensitivity in the MEMS electrothermal sensing since the method is not affected by amplitude variations that could arise from the readout circuit.