Injection molding could be used as a mass production technology for microlens arrays. It is of importance, and thus of our concern in the present study, to understand the injection molding processing condition effects on the replicability of microlens array profile. Extensive experiments were performed by varying processing conditions such as flow rate, packing pressure and packing time for three different polymeric materials (PS, PMMA and PC). The nickel mold insert of microlens arrays was made by electroplating a microstructure master fabricated by a modified LIGA process. Effects of processing conditions on the replicability were investigated with the help of the surface profile measurements. Experimental results showed that a packing pressure and a flow rate significantly affects a final surface profile of the injection molded product. Atomic force microscope measurement indicated that the averaged surface roughness value of injection molded microlens arrays is smaller than that of mold insert and is comparable with that of fine optical components in practical use.
acd Microswimmers, such as bacteria, are known to show different behaviours depending on their local environment. They identify spatial chemical gradients to find nutrient rich areas (chemotaxis) and interact with shear flows to accumulate in high shear regions. Recently, artificial microswimmers have been developed which mimic their natural counterparts in many ways. One of the exciting topics in this field is to study these artificial motors in several natural settings like the ones bacteria interact with. In this Focus article, we summarize recent observations of artificial swimmers in chemical gradients, shear flows and other interesting natural environments simulated in the lab using microfluidics and nanotechnology.
Complex-shaped microparticles (MPs) have attracted extensive interest in a myriad of scientific and engineering fields in recent years for their distinct morphology and capability in combining different functions within a single particle. Microfluidic techniques offer an intriguing method for fabricating MPs with excellent monodispersity and complex morphology in parallel while controlling their number and size precisely and independently. To date, there are two notable microfluidics approaches for the synthesis of complex-shaped MPs, namely droplet based, and flow-lithography based microfluidics approaches. It is undoubted that the application of complex-shaped MPs via microfluidic fabrication will hold great promise in a variety of fields including microfabrication, analytical chemistry and biomedicine.
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