Enhancing the Permeate Flux Improvement of Direct Contact Membrane Distillation Modules with Inserted S-Ribs Carbon-Fiber Filaments.

Three widths of manufacturing S-ribs carbon-fiber filaments acting as turbulence promoters were implemented into the flow channel of direct contact membrane distillation (DCMD) modules to augment the permeate flux improvement in the present study. Attempts to reduce the disadvantageous temperature polarization effect were made by inserting S-ribs turbulence promoters in improving pure water productivity, in which both heat- and mass-transfer boundary layers were diminished due to creating vortices in the flow pattern and increasing turbulence intensity. The temperature polarization coefficient ttemp was studied and found to enhance device performance (less thermal resistance) under inserting various S-ribs carbon-fiber thicknesses and operating both cocurrent- and countercurrent-flow patterns. The permeate fluxes in the DCMD modules with inserted S-ribs carbon-fiber turbulence promoters were investigated theoretically by developing the mathematical modeling equations and were conducted experimentally with various design and operating parameters. The theoretical predictions and experimental results exhibited a great potential to considerably achieve permeate flux enhancement in the new design of the DCMD system. The DCMD module with inserted S-ribs carbon-fiber turbulence promoters in the flow channel could provide a relative permeate flux enhancement up to 37.77% under countercurrent-flow operations in comparisons with the module of using the empty channel. An economic consideration on both permeate flux enhancement and power consumption increment for the module with inserted S-ribs carbon-fiber filaments was also delineated.

Moderate Signal Enhancement in Electrospray Ionization Mass Spectrometry by Focusing Electrospray Plume with a Dielectric Layer around the Mass Spectrometer's Orifice.

Electrospray ionization (ESI) is among the commonly used atmospheric pressure ionization techniques in mass spectrometry (MS). One of the drawbacks of ESI is the formation of divergent plumes composed of polydisperse microdroplets, which lead to low transmission efficiency. Here, we propose a new method to potentially improve the transmission efficiency of ESI, which does not require additional electrical components and complex interface modification. A dielectric plate-made of ceramic-was used in place of a regular metallic sampling cone. Due to the charge accumulation on the dielectric surface, the dielectric layer around the MS orifice distorts the electric field, focusing the charged electrospray cloud towards the MS inlet. The concept was first verified using charge measurement on the dielectric material surface and computational simulation; then, online experiments were carried out to demonstrate the potential of this method in MS applications. In the online experiment, signal enhancements were observed for dielectric plates with different geometries, distances of the electrospray needle axis from the MS inlet, and various compounds. For example, in the case of acetaminophen (15 µM), the signal enhancement was up to 1.82 times (plate B) using the default distance of the electrospray needle axis from the MS inlet (d = 1.5 mm) and 12.18 times (plate C) using a longer distance (d = 7 mm).

Partial Segregation of Bi and Microvoid Formation on a Pure Cu Substrate After Solid-Solid Reactions.

With the trend of technology development and carbon reduction, reducing the process temperature to prevent greenhouse effects is of great urgency. The back-end process of semiconductors is increasingly important because of the limitation of Moore's Law. High-temperature bonding is serious for semiconductor packages, which induces high cost and device damage. One of the critical ways to reduce the process temperature is to adopt low-temperature solders. In this study, we utilize the low-temperature solder Sn58Bi to achieve energy savings and device protection. The interfacial reactions between Sn58Bi and Cu after reflow and aging reactions were investigated. The solubility of Bi in Sn influences the Bi segregation at the interface. Partial Bi segregation, microvoids, and uneven Cu3Sn were observed at the interface after aging. There is no doubt that the aforementioned structures are unfavorable for solder joint strength.

Tuning Electrospray Ionization with Low-Frequency Sound.

Electrospray ionization (ESI) mass spectrometry (MS) is one of the key techniques used in biomolecular analysis nowadays. It relies on formation of polydisperse microdroplets, which undergo desolvation and liberate ions to the gas phase. Here we demonstrate low-frequency-sound-modulated ESI for analysis of biomolecules. By using a low-frequency (50-350 Hz) sound, it is possible to deflect electrospray microdroplets toward the mass spectrometer's orifice. Microdroplets of different sizes are deflected to a different extent leading to a partial size segregation. This effect leads to either an increase or decrease of MS signal intensity as well as signal-to-noise ratio. It also affects the selectivity of the ESI-MS analysis. The observations are rationalized by taking into account different pathways of ion formation and the likelihood of deflecting microdroplets of certain size. The online ESI-MS observations are supported with offline shadowgraphs obtained at varied sound frequencies, signal amplitudes, and phase shifts.