In situ monitoring and universal modelling of sacrificial PSG etching using hydrofluoric acid

A video system has been designed to monitor in situ and accurately the etching of sacrificial phosphosilicate-glass (PSG) microchannels using hydrofluoric acid (HF). An universal model, which predicts accurately the etching length vs. time over a wide range of HF concentration (3-49 wt.%), has been identified. In addition to diffusion, this model is based on a first-and-second order chemical reaction mechanism. It is found that the PSG microchannel etching rate in HF is sensitive to channel thickness but not width. Finally, bubble formation and movement inside the etched microchannels are observed. Most of the generated bubbles are mobile and can enhance the etching rate

Method of manufacturing an integrated electronic microphone having a floating gate electrode

Miniaturized microphones are used in a wide range of applications, such as cell phones, hearing aids, smart toys and surveillance devices. It would be desirable to design such microphones and manufacturing methods therefore that allow batch production and allow the integration of the microphone with miniaturized devices having other functions. Microfabrication of various types of miniature microphones has been explored. In the present invention, a device is proposed consisting of one or more microphones with micro-meter to milli-meter sized acoustic excitation pressure sensing membranes integrated with signal sensing and amplifying electronic elements. Acoustic excitation is converted to an electrical signal using a capacitor with an air-gap formed between a sensing membrane(sensing electrode) and a perforated rigid back-plate membrane(counter electrode). The capacitor can self-bias using charges permanently injected into an electrically floating electrode embedded inside one of the membranes. Alternatively, the capacitor can be biased externally. A process is now proposed to allow simultaneous realization of the mechanical component for acoustic pressure sensing and the electronic components for electrical signal processing is also proposed

On the stability of microchannel flow

A numerical investigation of the spectra of the Orr-Sommerfeld equation for plane Poiseuille flow in macro and micro channels is presented. The numerical approach is a modified method (with complex matrix pre-conditioning) to Orszag's (1971) pioneering approach. The results are compared with polar fluid where couple stresses effect is important. Both effects: couple stresses and velocity slip, are roughly equivalent to an apparent increase in the fluid viscosity. However, the slip-flow effect becomes more dominant as the channel size decreases and the critical Reynolds number decreases

Pharmacokinetic Analysis of Epithelial/Endothelial Cell Barriers in Microfluidic Bilayer Devices with an Air-Liquid Interface

As the range of applications of organs-on-chips is broadening, the evaluation of aerosol-based therapies using a lung-on-a-chip model has become an attractive approach. Inhalation therapies are not only minimally invasive but also provide optimal pharmacokinetic conditions for drug absorption. As drug development evolves, it is likely that better screening through use of organs-on-chips can significantly save time and cost. In this work, bio-aerosols of various compounds including insulin were generated using a jet nebulizer. The aerosol flows were driven through microfluidic bilayer devices establishing an air-liquid interface to mimic the blood-air barrier in human small airways. The aerosol flow in the microfluidic devices has been characterized and adjusted to closely match physiological values. The permeability of several compounds, including paracellular and transcellular biomarkers, across epithelial/endothelial cell barriers was measured. Concentration-time plots were established in microfluidic devices with and without cells; the curves were then utilized to extract standard pharmacokinetic parameters such as the area under the curve, maximum concentration, and time to maximum concentration. The cell barrier significantly affected the measured pharmacokinetic parameters, as compound absorption through the barrier decreases with its increasing molecular size. Aerosolizing insulin can lead to the formation of fibrils, prior to its entry to the microfluidic device, with a substantially larger apparent molecular size effectively blocking its paracellular transport. The results demonstrate the advantage of using lung-on-a-chip for drug discovery with applications such as development of novel inhaled therapies.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Effects of Embedded Sub-micron Pillar Arrays in Microfluidic Channels on Large DNA Electrophoresis

A study of the influences of embedding artificial structures in a microfluidic device for CE with a free buffer solution is presented. Compared with conventional slab-gel electrophoresis, three major additional effects on the overall system performance are identified when sub-micron pillar arrays are integrated into a standard CE microsystem. Since DNA molecules have to migrate in-between and interact with the pillars, pillar geometry is first demonstrated to have a direct impact on the DNA motion pattern. Electric field re-distribution is another inevitable outcome when features of sub-micron dimensions are placed inside a microchannel. This effect is verified by a numerical simulation tool. Furthermore, the integration of the closely packed sub-micron structures dramatically increases the surface to volume ratios in the microfluidic device and therefore generates a large EOF. The consequence of these additional influences implies a complexity in the measured DNA velocity and indicates that careful considerations have to be taken when these devices are used for DNA electrokinetics study or electrophoresis theory re-examination