Fabrication and testing of embedded microvalves within PMMA microfluidic devices

Abstract

The integration of a PDMS membrane within orthogonally placed PMMA microfluidic channels enables the pneumatic actuation of valves within bonded PMMA-PDMS-PMMA multilayer devices. Here, surface functionalization of PMMA substrates via acid catalyzed hydrolysis and air plasma corona treatment were investigated as possible techniques to permanently bond PMMA microfluidic channels to PDMS surfaces. FTIR and water contact angle analysis of functionalized PMMA substrates showed that air plasma corona treatment was most effective in inducing PMMA hydrophilicity. Subsequent fluidic tests showed that air plasma modified and bonded PMMA multilayer devices could withstand fluid leakage at an operational flow rate of 9 ll/min. The pneumatic actuation of the embedded PDMS membrane was observed through optical microscopy and an electrical resistance based technique. PDMS membrane actuation occurred at pneumatic pressures of as low as 10 kPa and complete valving occurred at 14 kPa for *100 lm by 100 lm channel cross-sections.

Integration of PDMS and PMMA for Batch Fabrication of Microfluidic Devices

“…It was not possible to treat PDMS-PMMA bonding 4 both surfaces with oxygen plasma to initiate irreversible bond. There are a number of technologies reported for bonding of PDMS to PMMA, notable by CVD process, surface modi¯cation by silane/silicate coatings and adhesives [12,13,14]. One of the methods of bonding PMMA to PDMS was modifying the mixture ratio of the PDMS elastomer and curing agent, followed by thermal bonding.…”

“…al. [12] spin coated the PDMS mixture onto a double-sided adhesive layer. This membrane was than sandwiched between two PMMA layers.…”

Miscible Organic Solvents Soak Bonding Method Use in a PMMA Multilayer Microfluidic Device

“…However, the microstructures can be damaged by thermal or pressure easily, since the temperature is kept around glass transition temperature (Tglass). Two methods are often used to solve this problem: reduce the bonding pressure or temperature by using surface modification technology [14][15][16][17][18] or add embedded filler layer to protection micro structures [19][20][21]. However, even without considering the complex modification process, the thermal and pressure cannot be effectively transmitted to the middle layer, in that case leakage occurs; while removing the filler layer of multilayer devices in second method is not easy either.…”

Molding and bonding of thermoplastic microfluidic devices

“…Another traditional method, corona discharge treatment also shows its potential in the surface modification of plastic parts, which uses discharge plasma to impact changes on the surface resulting in a more hydrophilic surface and then high bond strength [191][192][193]. However, corona discharge intensity is highly nonuniform over the treated surface as shown in Figure 2…”