BEH. 462/3.962J Molecular Principles of Biomaterials Spring 2003 o Microvalves for bioMEMS and lab-on-a-chip applications: 10 11 Utilize fast response of swelling in microsized ge to control flow through microfluidics o Example: PHEMA-Co-AA networks patterned in microfluidic channels outto Fgure 1 A diagram of and images demonstrating a varety of shapes that were poymenaed witn 35 seaons a, The fabricatio Figure 2 Prefabricated posts in a microchannel serve as support the posts. b, The actual dece after polymerization of the hydrogel. c, The hydrogel strucure with high-aspecH-tatio feature hydroges allow fluid to flow down the sde branch. e, The imp the hydrogel jacketdesign (ardes versus analtemative design that uses a singe larger erization of mut pe structures with a single exp cylindrical structure in the same size channel squarest. Io is the fractional change in lytic agent cells Figure 4 The volume response of two different hydrogels with respect to the pH of the surounding fluid. Top, the fractional change in diameter (D)of the hydrogels wihrespect outlet detection molecules to pH Bottom, images showing a device that directs(sorts )a fluid streamon the basis of its pH. The hydrogel gating the right branch (circles) expands in base and contracts in acid. The hydrogel gating the left branch (squares behaves in the opposite manner Figure 12 Lytic agent diffuses into the cell stream, lysing the cells and releasing the (expands n acid and contracts in base). the fluid enters from the centre channelatarate otein of interest. A small volume of the proteins are routed into the detection channel of 0.05ml min. At a pH of 7. 8, the flow is directed down the left branch. At a pH of 4.7, where molecules from a stream of detection reagent diffuse into the proteins, giving the flow s directed down the right branch. Both hydrogels expand to shut off the fow of a fluorescent signal. when the pH s changed to 6. 7. Scale bars, 300 um. Schematic shows an example lab-on-a-chip analysis approach Lecture 9-polyelectrolyte hydrogels 100f17BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o Microvalves for bioMEMS and lab-on-a-chip applications: 10,11 Utilize fast response of swelling in microsized gels to control flow through microfluidics o Example: PHEMA-co-AA networks patterned in microfluidic channels: • Schematic shows an example lab-on-a-chip analysis approach Lecture 9 – polyelectrolyte hydrogels 10 of 17