I. Introduction
Polydimethylsiloxane (PDMS) have been utilized as an elastomic molding substrate for the replication of microstructures from photolithography process [1]. PDMS consist of two main parts, which is the base part and the agent required for curing process. When both component are mixed together and cured at a specific temperature, the viscous polymer liquid crosslinks to change into a solid elastic structure. The introduction of PDMS as a core material for microfluidic devices as well as automated imaging techniques has made it possible to create miniature systems and devices well-suited for lab-on-chip application. Several unique properties of microfluidic devices that make them compatible as biomedical research tools are that: i) they require simple and cheap microfabrication techniques; ii) the use of transparent materials i.e. PDMS enables light transmission for optical imaging; iii) microfluidic devices has the ability to manipulate small amounts of liquids in small dimensions; iv) microfluidic devices also has the scalability to handle a large population of biological samples in high-throughput fashion; v) it is possible to integrate microfluidic devices with other available technology. A number of pioneering applications using microfluidic devices technology have been published [2]–[6]. Microfluidic devices fabrication process includes several steps of photolithography and chemical procedure. The microfluidic structure is created on a substrate, and after that the structure created will act as a mold and will be replicated by means of soft lithography technique. Negative photoresist such as SU-8 is normally used to produce the master mold. The dimension of the structure produced using soft lithography range from 30 nm to a couple hundred microns.
Process flow of soft lithography process and laser micromachine technique