A portable spectrophotometer has been developed to provide on-site detection of soybeans' moisture, protein and fat contents in a nondestructive manner. The core module of this soybean analyzer is a micro Fourier transform infrared spectrometer (μFTIR) based on an electrothermal microelectromechanical systems (MEMS) mirror. The electrothermal MEMS mirror is capable of generating a large piston motion of 320 μm at only 8.5 Vdc. The tilting of the MEMS mirror plate during its piston scanning affects the spectral repeatability of the μFTIR. In this paper, the effect of the MEMS mirror tilting on the spectral repeatability is analyzed and an automatic tilt realignment algorithm is developed to maintain high spectral repeatability which is better than 0.01 in long term use. The μFTIR module has a footprint of 125 mm x 90 mm with a height of 50 mm. The whole instrument is designed for portability and on-site operation as well as the convenience of loading soybeans. More than 300 samples of soybeans are collected, 80% of which are used to establish a prediction model using chemometrics methods. The standard error is no more than 3% when using the prediction model to test the remaining 20% samples.

Electrothermal actuation is one of the main actuation mechanisms and has been employed to make scanning microelectromechanical systems (MEMS) mirrors with large scan range, high fill factor, and low driving voltage, but there exist long-term drifting issues in electrothermal bimorph actuators whose causes are not well understood. In this paper, the stability of an $\mathrm{Al}/{\mathrm{SiO}}_2$ bimorph electrothermal MEMS mirror operated in both static and dynamic scan mode has been studied. Particularly, the angular drifts of the MEMS mirror plate were measured over 90 h at different temperatures in the range of $50$ – $150$ °C. The experiments show that the temporal drift of the mirror plate orientation largely depends on the temperature of the electrothermal bimorph actuators. Interestingly, it is found that the angular drift changes from falling to rising as the temperature increases. An optimal operating temperature between $75$ °C to $100$ °C for the MEMS mirror is identified. At this temperature, the MEMS mirror exhibited stable scanning with an angular drift of less than $0.0001$ °/h.

An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, fabricated and utilized. With appropriate installation of the sensor and bearings on the table, the engine rotor can be driven to rotate with the sensor using a silicon lever beam. One end of the beam is fixed to the shaft of the gas bearing, while the other end is free and in contact with the sensor probe tip. When the sensor begins to rotate with the table, the beam is pushed by the sensor probe to rotate in the same direction. For the beam, the friction torque from the gas bearing is balanced by the torque induced by pushing force from the sensor probe. Thus, the friction torque can be calculated as a product of the pushing force measured by the sensor and the lever arm, which is defined as the distance from the sensor probe tip to the centerline of the bearing. Experimental results demonstrate the feasibility of this system, with a sensitivity of 1.285 mV/μN·m in a range of 0 to 11.76 μN·m when the lever arm is 20 mm long. The measuring range can be modified by varying the length of the lever arm. Thus, this system has wide potential applications in measuring the micro-friction torque of gas bearings in rotating MEMS machines.

Carrier transport in colloidal quantum dot (CQD) films is strongly influenced by the interfacial coupling between CQDs. Currently, the shape of PbS CQDs synthesized using traditional methods results in random orientation relationships between the crystal facets in CQD films, limiting the coupling strength and the final performance of optoelectronic devices. In this study, post-synthesis surface treatment of PbS CQDs was employed to achieve facet control during secondary growth, manipulating the facets of PbS CQDs at the nanoscale to enhance interfacial coupling within CQD films. Additionally, mixed ligands of (X = Br, I) and anhydrous sodium acetate were used to passivate the PbS CQDs, ensuring sufficient passivation.This method combines facet passivation with strong coupling through the (100) facets of CQDs, thereby enhancing carrier mobility and improving device performance. Experimental results showed that, compared to standard PbS CQD films, the electron and hole mobilities of the PbS CQD films subjected to secondary growth were significantly improved, with hole mobility increased by 6 times. Photodetectors fabricated using these films achieved a quantum efficiency of 33% at 1500 nm under 0V bias, a threefold improvement compared to standard devices.

Colloidal quantum dots have been widely applied in various optoelectronic devices such as solar cells, photodetectors, and light emitting diodes. The measurement of carrier dynamics not only allows the study of the passivation quality of quantum dot surfaces but also contributes to analyze the performance of related devices. In this study, by measuring and comparing the photocarrier radiometry signals of PbS quantum dot films on different substrates from the same batch, we investigated the carrier transport and trap properties in the material. First, based on the differences in surface recombination velocities of colloidal quantum dot films on different substrates, we established a theoretical model of differential photocarrier radiometry technique applicable to colloidal quantum dot films. We simulated and analyzed the effects of the carrier transport parameters, such as carrier lifetime, carrier hopping diffusivity, and surface recombination velocities, on the differential photocarrier radiometry signals. Finally, the photocarrier radiometry signals of PbS quantum dot films on K9 glass substrate and transparent indium tin oxide film coated glass substrate were experimentally measured, and the carrier transport parameters of the quantum dot films were also obtained through multiparameter fitting. The simulation and experimental results demonstrate that the differential photocarrier radiometry technique can be used for non-destructive measurement of the carrier transport and trap properties of colloidal quantum dot films without the adverse effects of instrument frequency response.