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When fluids flow through straight channels sustained turbulence occurs only at high Reynolds numbers [typically Re∼O(1000)]. It is difficult to mix multiple fluids flowing through a straight channel in the low Reynolds number laminar regime [Re<O(100)] because in the absence of turbulence, mixing between the component fluids occurs primarily via the slow molecular diffusion process. This Letter reports a simple way to significantly enhance the low Reynolds number (in our case Re≤10) passive microfluidic flow mixing in a straight microchannel by introducing asymmetric wetting boundary conditions on the floor of the channel. We show experimentally and numerically that by creating carefully chosen two-dimensional hydrophobic slip patterns on the floor of the channels, we can introduce stretching, folding, and/or recirculation in the flowing fluid volume, the essential elements to achieve mixing in the absence of turbulence. We also show that there are two distinctive pathways to produce homogeneous mixing in microchannels induced by the inhomogeneity of the boundary conditions. It can be achieved either by (1) introducing stretching, folding and twisting of fluid volumes, i.e., via a horse-shoe type transformation map, or (2) by creating chaotic advection, achieved through manipulation of the hydrophobic boundary patterns on the floor of the channels. We have also shown that by superposing stretching and folding with chaotic advection, mixing can be optimized in terms of significantly reducing mixing length, thereby opening up new design opportunities for simple yet efficient passive microfluidic reactors. 

Microbial fuel cells (MFCs) are clean, renewable energy sources and they generate self-sustaining clean energy through cellular respiration. MFCs do not require any external energy to operate and do not emit any excess greenhouse gases. MFCs can also be used for bioremediation by removing toxic materials by respiring a variety of metals and other harmful elements including iron and uranium. In this article, we have discussed the principles and designs of biofuel cells. 

Cellular respiration is the process by which organic matter oxidizes, and the energy stored in the chemical bonds of the food releases. Normally, cellular respiration occurs inside the mitochondria of cells; however, a unique type of bacteria releases electrons externally. These specialized organisms are called electrogenic bacteria. Our goal is to construct a microbial fuel cell (MFC) with electrogenic bacteria, harvest the external electrons created by cellular respiration, and channel them through an external circuit to generate electricity. Mud soil, which has a high number of electrogenic bacteria in the environment, was used to construct an MFC. In the presence of gram-negative bacteria, which exist in both aerobic and anaerobic conditions, the constructed MFC delivered electrical energy to an external circuit. The MFC can generate electricity, and thereby power, from biodegradable substances and organic wastes found in the environment and landfills. They can also be used to power small devices and sensors used in day-to-day activities. To determine the effect of sugar on the growth and development of bacteria present in the MFC, the quantity of sugar administered will be monitored in relation to the power generated per day. 

This paper describes a holistic pedagogical approach for classroom engagement. The project translates theory and fundamental classroom knowledge to authentic application with cutting edge research implemented by undergraduates at a Historically Black University. In our project, we developed and assessed cartoons custom designed for classroom instruction and evaluated student engagement while using the cartoons. We further report on student successes achieved through undergraduate research projects. 

Dye sensitized solar cells are a type of thin film solar cell used to convert sunlight into electrical energy. These devices use a different mechanism than conventional solar cells and can be made from materials which are biocompatible and biodegradable. The simplicity of design and small environmental impact of these devices make them a likely candidate for replacing conventional PV devices. Since these solar cells are thin film cells, they can be made to be transparent and can be printed on flexible substrate, allowing their incorporation into many household objects such as windows, backpacks, walls, and other objects which would otherwise not be used for energy generation. A wide variety of fabrication techniques and device designs exist for DSSCs, each having its benefits and deficiencies; it is the purpose of this paper to evaluate some of these design variations, including different semiconductor and dye types and scaffolds, as well as semiconductor surface treatment. 

Dye sensitized solar cells are a type of thin film solar cell used to convert sunlight into electrical energy. These devices use a different mechanism than conventional solar cells and can be made from materials which are biocompatible and biodegradable. The simplicity of design and small environmental impact of these devices make them a likely candidate for replacing conventional PV devices. Since these solar cells are thin film cells, they can be made to be transparent and can be printed on flexible substrate, allowing their incorporation into many household objects such as windows, backpacks, walls, and other objects which would otherwise not be used for energy generation. A wide variety of fabrication techniques and device designs exist for DSSCs, each having its benefits and deficiencies; it is the purpose of this paper to evaluate some of these design variations, including different semiconductor and dye types and scaffolds, as well as semiconductor surface treatment using microwave plasma.