3.4 Sealing(Lidding) For the microfluidics device to be functional, the embossed channels on the COC plate have to be laminated with a thin film so that the channels will be roofed in order to make experimenting with chemical solutions inside the device possible. Thus, bonding is a critical step in thermoplastic fabrication process, as well as for PDMS devices. However, it is also the most difficult process as well. There are several ways to lid the microfluidics device, such as thermal fusion bonding, adhesive bonding, solvent bonding, welding, and surface treatment and modification, but these methods take quite long to be performed. So in order to shorten the fabrication time for this COC crystallography microfluidics device we have decided to use chemical vapor sealing method, which is using the vapor from cyclohexane solution heated at 36 °C to melt a certain thickness of a blank COC sheet, and then applying that layer on top of the embossed piece. Upon contact with another piece of COC piece, the melted layer of COC sheet will form polymerize with the adjoining polymers of the embossed piece, resulting in an extremely strong bonds. Figure 3-1 represents a simple schematic of sealing a microfluidics device for a better understanding for the readers. Cyclohexane was used as our chemical solvent, because it is known to be reactive with COC. Materials used during this process are electronic hot plate, a 5ml glass syringe, cyclohexane solution, and a two-level chamber lidding device, which I have personally designed and manufactured. A schematic diagram of our lidding plate is shown below: Figure 2. Three-dimensional design of the two-layer chambered lidding plate. It has two layers on top of each other: the yellow bottom layer is for storing cyclohexane, and the layer above is the pathway for vapor to climb up and react with the polymers on the surface of blank COCs. The top frames are for placing a microscope slide with an empty COC sheet taped on at the middle of the glass slide, and then that COC sheet acts as a cap for the top chamber opening in order to maintain a steady and continuous exposure to cyclohexane vapor. Ideal condition for chemical vapor bonding process:
3.4 Sealing(Lidding) For the microfluidics device to be functional, the embossed channels on the COC plate have to be laminated with a thin film so that the channels will be roofed in order to make experimenting with chemical solutions inside the device possible. Thus, bonding is a critical step in thermoplastic fabrication process, as well as for PDMS devices. However, it is also the most difficult process as well. There are several ways to lid the microfluidics device, such as thermal fusion bonding, adhesive bonding, solvent bonding, welding, and surface treatment and modification, but these methods take quite long to be performed. So in order to shorten the fabrication time for this COC crystallography microfluidics device we have decided to use chemical vapor sealing method, which is using the vapor from cyclohexane solution heated at 36 °C to melt a certain thickness of a blank COC sheet, and then applying that layer on top of the embossed piece. Upon contact with another piece of COC piece, the melted layer of COC sheet will form polymerize with the adjoining polymers of the embossed piece, resulting in an extremely strong bonds. Figure 3-1 represents a simple schematic of sealing a microfluidics device for a better understanding for the readers. Cyclohexane was used as our chemical solvent, because it is known to be reactive with COC. Materials used during this process are electronic hot plate, a 5ml glass syringe, cyclohexane solution, and a two-level chamber lidding device, which I have personally designed and manufactured. A schematic diagram of our lidding plate is shown below: Figure 2. Three-dimensional design of the two-layer chambered lidding plate. It has two layers on top of each other: the yellow bottom layer is for storing cyclohexane, and the layer above is the pathway for vapor to climb up and react with the polymers on the surface of blank COCs. The top frames are for placing a microscope slide with an empty COC sheet taped on at the middle of the glass slide, and then that COC sheet acts as a cap for the top chamber opening in order to maintain a steady and continuous exposure to cyclohexane vapor. Ideal condition for chemical vapor bonding process:
Hong_Thesis.docx