Papers by Author: Zhi Ping Wang

Abstract: A rapid manufacturing process was demonstrated to fabricate a microfluidic device to amplify specific DNA fragments in less than 8 hours. Microfluidics was derived from microelectromechanical system (MEMS) with lithography technique on the substrates of silicon and glass, which made the microfluidic product have a higher fabrication cost and laborious fabrication steps. This rapid approach only requires three steps for a PDMS microfluidic device: metal mold insert manufacturing, PDMS casting, and glass bonding. Each step did not require complicated equipments or procedures, and make this approach very attractive in rapid prototyping and experimental optimization with microfluidic devices. In this work, a brass mold insert was manufactured by a micromilling machine, followed by the standard PDMS casting and glass bonding to fabricate a microfluidic device. Polymerase chain reaction (PCR) to amplify specific DNA fragments, a typical microfluidic example, was successfully realized on this PDMS microfluidic device. This rapid and low cost (compared to conventional lithography) fabrication approach can provide researchers a lower entry to polymeric lab-on-a-chip either on PDMS or thermoplastic substrate for various applications.

Abstract: The sealing of microchannels is a key step in the fabrication of microfluidic devices and thermal bonding is a common technique used. Here, major manufacturing issues and considerations in thermal bonding are investigated, including bonding quality and microchannel deformations. Flatness of substrate is extremely crucial to the uniformity in bonding. While increased bonding pressure helps to overcome problems related to surface topography and to enhance bond strength, its significant impact on geometrical changes of microchannel due to viscoelastic effect should also be taken into consideration.

Abstract: UV micro-casting is a promising mass production method for replication of polymeric microdevices due to the non-stringent process conditions and fast curing time. This paper describes a potential method to mass produce polymeric microdevices. The first generation mold for UV micro-casting was fabricated by using chemically micro-etched copper clad laminate (CCL) base substrate. Subsequently a two part silicone rubber was cast over the CCL micro-feature mold. Photosensitive resin was dispensed onto the silicone rubber mold and a transparent Mylar thin film was placed on top of the UV curable prepolymer. After the silicone rubber mold-resin-Mylar assembly was UV irradiated for tens of seconds, the crosslinked polymer, together with the Mylar film was peeled off from the mold. The cross-linked polymer was placed on top of a second layer of Mylar film dispensed with the similar UV curable resin. In this way, a complete polymeric micro device could be efficiently produced.