![]() ![]() For example a PET membrane that is sandwiched between two PDMS layers. ![]() A 3-layer microfluidic device means the device is made of three physical layers. A “three layer mold” is different from a “three layer microfluidic device”. There is often confusion when clients communicate with the manufacturer about multi-layer stuff. A microfluidic channel with constant depth needs a single layer mold, while the above two step channel requires a two-layer mold. Or changes step-wise, eg is 100um until a junction and then becomes 200um to the end. For example when depth changes like a slope from 100um to 200um. But the depth may also need to change from inlet to outlet. As an example, where all channels have 100um depth. In most cases in Microfluidics the depth is constant. Longitudinal profile relates to how the depth varies along the microfluidic channel. For example a 50um wide channel that is 50um deep! The best rectangular cross section for microfluidic channels’ manufacture is a square. This means the mold would get stuck deep in the microfluidic channel and would either break upon ejection or damage the microchannel. Too narrow microchannel design causes de-molding issues. On the other hand, a too narrow channel is created when the width is much smaller than the depth. In this case, the channel top and bottom might collapse on each other, and close the channel. A very wide channel in which the width is much larger than the depth, would cause problems during bonding and sealing. Avoid too wide microfluidic channel or too narrow channels. Best cross section: rectangle, or square. Larger channels with such trapezoidal cross section might be built using CNC micromilling, but most microfluidic channel cannot be made with such slanted bottoms. In your microfluidic design if the cross section has a slope along the channel width (varying depth), be worried. ![]() It is very very difficult to obtain rounded cross sections. Most microfluidic molds are made using etching, lithography, electroplating, CNC micromilling. Avoid semi circular cross section as much as possible too. This means to make a circular cross section, two semi-circular channels need to be perfectly aligned on top of each other. The microfluidic channels are made by layering. To illustrate, if you miniaturize yourself and travel Sci-Fi style into a microchannel, then the cross section is the frame you would see when you are looking along the channel? This could be a square, rectangle, circle, semi-circle, or trapezoid.ĭesign Tips: Avoid circular cross section. If the chip is sliced somewhere along the channel, then the cross section of the channel is revealed. In all these cases the microfluidic channels facilitate the way out. These devices often don’t let the liquid out, but there is a waste chamber within the cartridge that collects the reagents and the specimen. ![]() The exception to the above situations is the case of diagnostic cartridges. Another example of product needing to be delivered out of the chips is liquid mixtures produced in micromixing devices. For example in droplet microfluidics, the microchannel must reliably deliver the droplets and their encapsulated contents out of the chip for downstream processing. Not all fluid transported out of the microfluidic chip is waste. Other example of waste is when a washing media is applied to micropartciles trapped in the microfluidic device. After food and possibly drug is fed to them, cells’ waste and the leftover of food must be taken out continuously. For example in organ-on-a-chip or tissue chips, where the cells are cultured inside a microfluidic chip. Not in all cases but in most of them, the microfluidic channel needs to take the liquid waste or product out as well. In all these cases microchannels are involved. Finally, the liquid might be a compound for chemical synthesis such as monomers, or extraction such as organic solvents. Similarly, the fluid may deliver chemicals or reagents such as drugs, dyes, enzymes, or nutrition. Alternatively, the liquid may just carry microparticles such as cells, organoids, hydrogel beads, or magnetic beads. Or it could be a liquid specimen such as blood, sweat, saliva, urine, semen, or sewage water. The liquid could be a plain media such as PBS, water, or oil. The main function of a microfluidic channel is to bring liquid into the device. Essential Microfluidic Techniques for Droplet ManipulationĪny continuous microfluidic device must have at least one Microchannel also known as Microfluidic channel.Designing a Droplet Microfluidic Experiment.Immobilization and Positioning Techniques.Design parameters for microfluidics organ on a chips. ![]()
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