Microfluidic spinning

Confocal laser scanning microscopy (CLSM) MicroChannel Microfluidics Spinning-disk confocal microscopy... 

There are three types of mass transport processes within a microfluidic system convection, diffusion, and immigration. Much more common are mixtures of three types of mass transport. It is essential to design a well-controlled transport scheme for the microsystem. Convection can be generated by different forces, such as capillary effect, thermal difference, gravity, a pressurized air bladder, the centripetal forces in a spinning disk, mechanical and electroosmotic pumps, in the microsystem. The mechanical and electroosmotic pumps are often used for transport in a microfluidic system due to their convenience, and will be further discussed in section 11.5.2. The migration is a direct transport of molecules in response to an electric field. In most cases, the moving... 

CPC Spin Columns with Matrixless MALDI-MS and Gyros CPC Microfluidic ESI/MALDI-MS System... 

In the next step we are form the walls of the channels in the microfluidic device. A new, very special polymer is spin-coated on the substrate to the desired thickness. This polymer differs from the inexpensive photoresist because it comes into contact with the later fluid. Therefore, it should have a long stability it should not form cracks, should be stable against different chemicals and it should be hydrophilic or easily hydrophilized, because otherwise water will not run through the channel. Again a photo-sensitive material is used, but this time the later channel is photochemically modified. A perfect material to use is SU-8. For details see Refs. [450,451], This part can be washed away afterwards. 

Ultra-thick microfluidic stmctures (up to 1.5 mm high) were fabricated using SU-8 photoresist. Instead of using a spin-coater, a constant-volume injection method was used to apply thick photoresist for patterning [237]. 

Since then, various methods have been adopted for fabrication of photoresist-based microfluidic devices. The first method shown in Figure 20.9a begins with a spin coating of photoresist onto a substrate and patterning with a photomask." Once the open microchannels are created, a sacrificial material is filled into the space of the microchannel. Subsequently, a second layer of photoresist is spin coated and patterned on top to define the access holes for inlet and outlet. Finally, the sacrificial layer is dissolved to create the closed microchannels. The major disadvantage in this process is the slow dissolution, therefore only short microchannels are applicable. 

At the early stage of the development of the heart-on-a-chip, a PDMS microfluidic network was combined with planar electrode array to measure the extracellular potential from individual adult cardiomyocytes [54]. Another microfluidic device with an array of electrodes was developed to electrically measure the metabolic profile of cardiomyocytes and optically measure cell contractility [55]. Grosberg et al. first introduced a tissue level heart-on-a-chip to measure the contractility of neonatal cardiac muscle tissue [52]. In the design, eight muscular thin films (MTF) were fabricated on a chip. A layer of poly(N-isopropylacrylamide) (PIPAAm) dissolved at below 35 °C is spin-coated on top of a glass slide (Fig. 5A). Subsequently, a PDMS layer was coated on top of the PIPAAM layer. The PDMS layer was used to seed neonatal rat ventricular cardiomyocytes. The substrate seeded with cells is placed in the bath and the film layers were manually cut to fabricate an array of two opposite rows of four rectangular film layers of MTFs. The MTFs are peeled off after PIPAAm is dissolved as a solution when kept below 35 °C. Finally, electrodes are placed on the top and the bottom of MTFs. 

In one of the most complete microfluidic systems developed for mass spectrometry applications to date, Gustafsson et al. [12] developed a MALDI interface for compact disk (CD)-based microfluidics, a technology in which reactions and separations are powered by centrifugal forces on a spinning device (CD Lab-on-a-Chip). Figure 3b demmistrates the operation of an individual analysis region (each CD contains 96 such regions). The sample is loaded (A) and then washed and eluted from a reversed-phase colunm (B). Finally, the sample is co-crystaUized with... 

Centrifugal microfluidics Label-based detection Label-free detection Lab-on-a-disc Optical detection Optical disc drive Spinning disc interferometry... 

Optical Detection on Centrifugal Microfluidic Lab-on-a-Disc Platforms, Fig. 4 Detection principal and optical setup of spinning disc interferometry on the Bio-CD platform [8] ( American Institute of Physics)... 

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