Capacitors made of interdigitated electrodes (IDEs) as a transducer platform for the sensing of volatile organic compounds (VOCs) have advantages due to their lower power operation and fabrication using standard micro-fabrication techniques. Integrating a micro-electromechanical system (MEMS), such as a microhotplate with IDE capacitor, further allows study of the temperature-dependent sensing response of VOCs. In this paper, the design, fabrication, and characterization of a low-power MEMS microhotplate with IDE capacitor to study the temperature-dependent sensing response to methanol using Zeolitic imidazolate framework (ZIF-8), a class of metal-organic framework (MOF), is presented. A Titanium nitride (TiN) microhotplate with aluminum IDEs suspended on a silicon nitride membrane is fabricated and characterized. The power consumption of the ZIF-8 MOF-coated device at an operating temperature of 50 ${}^{\circ }$ C is 4.5 mW and at 200 ${}^{\circ }$ C it is 26 mW. A calibration methodology for the effects of temperature of the isolation layer between the microhotplate electrodes and the capacitor IDEs is developed. The device coated with ZIF-8 MOF shows a response to methanol in the concentration range of 500 ppm to 7000 ppm. The detection limit of the sensor for methanol vapor at 20 ${}^{\circ }$ C is 100 ppm. In situ study of sensing properties of ZIF-8 MOF to methanol in the temperature range from 20 ${}^{\circ }$ C to 50 ${}^{\circ }$ C using the integrated microhotplate and IDE capacitor is presented. The kinetics of temperature-dependent adsorption and desorption of methanol by ZIF-8 MOF are fitted with double-exponential models. With the increase in temperature from 20 ${}^{\circ }$ C to 50 ${}^{\circ }$ C, the response time for sensing of methanol vapor concentration of 5000 ppm decreases by 28%, whereas the recovery time decreases by 70%.

An fF-level capacitive sensor, intended for pL liquid measurements, has been fabricated with MEMS technology and successfully characterized. The sensor measures liquid level variations in a microfluidic channel. The sensor’s capacitance varies from 1.5 fF (channel empty) to 12.8fF (channel filled with 63 pL of water). To reliably detect such small capacitance changes, a low noise measurement system, based on a lock-in amplifier, was implemented. The measured sensitivity of the system is 14.1 mV/fF, and the capacitance detection limit is 0.057 aF/Hz^1/2, which corresponds to a volumetric resolution of about 0.22 fL/Hz^1/2.

This paper presents for the first time, the integration of ultra-thin (<10 nm) atomic layer deposition (ALD) aluminum oxide (Al₂O₃) membranes as electron transparent windows (ETWs) for transmission electron microscope (TEM) nanoreactor applications. The process was successfully implemented and tested in a TEM. ETWs with thicknesses down to 5 and 10 nm were used to image nanoparticles (NPs) in a 120 keV TEM and 200 keV TEM respectively.

This paper presents a submicron suspended piezoresistive silicon-beam structure as a basic sensing element to replace the conventional piezoresistors, so to improve the detection sensitivity. The alternative element benefits from the increase of the induced stress, which is locally concentrated on the suspended submicron beam. This approach allows the enhancement of sensitivity without modifying the parameters in the mechanical design. A modified deep reactive- ion etching process is developed to create both the suspended silicon-beam and the main mechanical structure in a single etching sequence. With the new element, sensitivity up to 52.5 V/N is obtained, corresponding to a 120% improvement compared to an equivalent structure with conventional piezoresistors.