The use of nanoparticles has been growing in various industrial fields, and concerns about their effects on health and the environment have been increasing. Hence, characterization techniques for nanoparticles are essential. Here, we present a silicon dioxide microfabricated suspended microchannel resonator (SMR) to measure the mass and concentration of nanoparticles in a liquid as they flow. We measured the mass detection limits of the device using laser Doppler vibrometry. This limit reached a minimum of 377 ag that correspond to a 34 nm diameter gold nanoparticle or a 243 nm diameter polystyrene particle, when sampled every 30 ms. We compared the fundamental limits of the measured data with an ideal noiseless measurement of the SMR. Finally, we measured the buoyant mass of gold nanoparticles in real-time as they flowed through the SMR. [Figure not available: see fulltext.].

We report the design, fabrication and experimental investigation of a MEMS micro-hotplate (MHP) for fast time-resolved X-ray diffraction (TRXRD) study of Cu nanoparticle paste (nanoCu paste) sintering process. The device and its system are designed to have a 60 ms minimum time interval, uniform temperature distribution and variant gas environments. A TRXRD study of nanoCu paste sintering at 200 °C in H₂-N₂ gas mixture was done using this device. With 1 sec interval, Cu₈O reduction and Cu crystallization in sintering is observed. Results can be combined with other studies to optimize material design and process development.

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 ∘ C is 4.5 mW and at 200 ∘ 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 ∘ C is 100 ppm. In situ study of sensing properties of ZIF-8 MOF to methanol in the temperature range from 20 ∘ C to 50 ∘ 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 ∘ C to 50 ∘ C, the response time for sensing of methanol vapor concentration of 5000 ppm decreases by 28%, whereas the recovery time decreases by 70%.

The mechanical part of inertial sensors can be designed to have a large mechanical sensitivity, but also requires the transduction mechanism which translates this displacement. The overall system resolution in mechanical inertial sensors is dictated by the noise contribution of each stage and the magnitude of each sensitivity, see also Figure 1. Maximizing the capacitive sensitivity, results in suppression of noise in the electronics domain. This work focuses on the design and realization of a mechanical to electrical transduction using a capacitive readout scheme. Design considerations and measures are taken to maximize the latter are considered and illustrated using FEM simulations. A capacitive transducer showing a sensitivity of 100 [aF/nm] was designed and realized, by exploiting the large displacement behavior of the inertial sensor which was considered.

This work describes the design, modelling and realisation of the mechanical part of a non-linear MEMS accelerometer intended for large displacement behaviour. For this, a mass/spring system was designed with an extremely low resonance frequency. In this work the mechanical behaviour was verified by measurements done using an optical setup, including a laser and photodiode. The results are a resonance frequency of 12.6 Hz, which can be further tuned depending on the application by varying the mass, beam thickness and tilt of the structure. This results in a mechanical sensitivity of 0.16 [mm/ms-2]. The future goal of this work is to integrate a read-out scheme on wafer level, for example electrostatically.

The in situ electrochemical growth of Cu benzene-1,3,5-tricarboxylate (CuBTC) metal-organic frameworks, as an affinity layer, directly on custom-fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5-7 μm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 μm and a height of 6-8 μm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion-controlled kinetics (k = 2.9 mmol s^-0.5 g^-1 _CuBTC). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity K_e = 174.8 bar^-1. A volume fraction f_MeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu-IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100-8000 ppm.

This paper presents the effect of an arbitrary interruption of the propagation path in Surface Acoustic Wave (SAW) microdevices on the intensity of the scattered surface waves. Using finite element modeling, simulations have been carried out to validate a new equivalent circuit based on the conventional Mason and Smith model. In addition, experimental results obtained with 30, 50 and 100 μm diameter microholes are reported. The comparison of theory, simulation and experiment proves that it is possible to fabricate an interruption like deep microcavities or microholes in the propagation path which results in an acceptable signal magnitude attenuation, but without shift in the operating frequency.

Although color shift is one of the key issues to be considered for the failure of LEDs products, there is limited literature that correlated LED products' lifetime performance to their color shift over time. This is mainly due to the lack of a suitable model to define the color shift over time. In this paper, a methodology for characterizing and predicting the color shift of the polycarbonate materials in LED products is developed. It had shown that the color shift follows the 1st order reaction. Furthermore, the rate coefficient k of the reaction was found to follow Arrhenius relationship with activation energy of 0.046eV.