Several bacterial species possess the ability to attach to surfaces and colonize themselves in thin films called biofilms. Biofilms that grow in porous media are relevant to several industrial and environmental processes such as wastewater treatment and CO2 sequestration. We used Pseudomonas fluorescens , a gram negative aerobic biofilm forming bacteria, to investigate biofilm formation in a microfluidic porous media mimic device. The microfluidic device consists of an array of micro-posts, which were fabricated using soft-lithography. Subsequently, biofilm formation in this device was investigated as a function of time and the formation of filamentous biofilms known as streamers was observed. Furthermore, we used computational fluid mechanics simulation to better understanding of the streamer formation.

In this paper, a batch of microfluidic-based reactors with integrated micropillars was fabricated on silicon wafer with standard optical lithography and deep reactive-ion etching (DRIE) technique. A Bosch process of DIRE was used to obtain ∼ 85 μm etching depth and undulating sidewall profiles on the surface of those micropillars. Such structures boost surface-area-to-volume-ratio as well as enhance heat and mass transfer coefficients. Platinum (Pt) nanoparticles (NPs) stabilized by poly-acrylate sodium in a water-ethonal-based suspension were deposited on the reactor surface using a surface-selective infiltration method. By introducing methanol vapor/air gas mixture into the reactors, stable catalytic combustion of methanol over Pt NPs starting from room temperature can be achieved.

This paper presents an Euler-Bernoulli microcantilever beam model utilized in non-contact Atomic Force Microscopy (AFM) systems. A distributed-parameters modeling is considered for such system. The motions of the microcantilever are studied in a general Cartesian coordinate with an excitation at the base such that beam end with a tip mass is subject to a general force. This general force comprising of two attractive and repulsive parts with high power terms is taken as the atomic intermolecular one which has a relation with the displacement between the tip mass and the surface such that the total general force will be in the form of an implicit nonlinear equation. It is most desired to observe the effects of the base excitation in high frequencies on the tip van der Waals interaction force. Hence, the general force will produce a peak in the FFT spectrum corresponding to the frequency of the base.

A label-free technique capable of rapidly screening human blood samples simultaneously for multiple serum tumor markers would enable accurate and cost-effective diagnosis of cancer before physiological symptoms appear. Recently, microfabricated, bimaterial cantilever sensors have been demonstrated to detect DNA hybridization and antigen-antibody binding at clinically relevant concentrations. Cantilever sensors deflect measurably under the surface stress resulting when biomolecules immobilized on one surface of the sensor interact with their binding partners [1]. We present an array of cantilever sensors (silicon nitride with a gold coated surface) capable of simultaneously interrogating 100 different biomolecular interactions.

Burning or combustion is the most common energy conversion method of which the chemical energy stored is converted to the thermal energy during an oxidation process. Governed by the scaling and thermodynamic laws, there is a minimum size requirement (∼1 mm) for having a sustainable reaction. Conventional combustion or burning usually takes place when the reactants’ temperature is much higher than the body temperatures of biological beings. All heat engines including both external combustion engines and internal combustion engines were developed using this phenomenon; and reaction processes proceed in macroscale where big machines and large reaction chambers are often employed. As an attempt to mimic nature’s method of energy conversion, without external ignition, nano-catalytic particles could be self-heated very rapidly (in seconds) in the present of methanol or ethanol vapor/air mixture flow. Stable and reproducible spontaneous self-ignition and self-supporting combustion have been achieved at room temperature by exposing nanometersized catalytic particles to methanol-air or ethanol-air gas mixtures. Infrared thermography revealed that the thermal gradient near nanoparticles could be more than 100 times higher than what could be achieved in macroscale. The reaction releases heat and produces CO 2 and water. Such reactions starting at ambient temperature have reached both high (> 600°C) and low (a few tenths of a degree above room temperature) reaction temperatures. The reaction intensity could be easily controlled by varying the fuel-air mixture. The application of this discovery might lead to the development of a new class of solid state electrical power generators which could convert fuel energy to electricity without any moving parts.