We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ∼20 MHz to ∼38 GHz. The effective quality factor ( ) of the sensor is as high as ∼3.8 × 10 with 200 l of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ∼1 GHz to ∼10 GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements.
A highly tunable and sensitive radio-frequency (RF) sensor is presented for the measurement of aqueous-solution dielectric properties. Two quadrature hybrids are utilized to achieve destructive interference that eliminates the probing signals at both measurement ports. As a result, weak signals of material-under-test (MUT) are elevated for high sensitivity detections at different frequencies. The sensor is demonstrated through measuring 2-propanol-water solution permittivity at 0.01 mole fraction concentration level from ~4 GHz to ~12 GHz. De-ionized water and methanol-water solution are used to calibrate the sensor for quantitative MUT analysis through our proposed model. Micro-meter coplanar waveguides (CPW) are fabricated as RF sensing electrodes. A polydimethylsiloxane (PDMS) microfluidic channel is employed to introduce 250 nL liquid, of which ~1 nL is effectively the MUT. The permittivity and the relaxation time of 2-propanol-water solution are obtained. Compared with our power divider based sensors, the differential reflection coefficients in this work provide additional information that complements the transmission coefficient methods.
Physic-based materials design often relies on a fundamental understanding on the structure and property relations of materials. By introducing various stimuli into the transmission electron microscope (TEM) sample chamber, in-situ TEM has enabled researchers to carry out experiments directly in the TEM, leading to extensive discoveries on the atomic-scale dynamic processes of materials and crucial mechanistic insights on the origin of material’s behaviors such as size-effect in gold catalysis, toughening mechanism of high entropy alloys, and degradation mechanisms of battery materials. The findings have profoundly impacted the materials science and engineering. In this review, we will briefly introduce the instruments associated with in-situ TEM including the environmental TEM, heating, illumination, biasing, straining devices, and irradiation capabilities. Then, typical applications of these various in-situ TEM capabilities will be discussed. Finally, we will summarize the shortcomings and envision the future of in-situ TEM technologies especially those for the study of catalysis.
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