Investigation of factors affecting the channel sealing processing mode of microfluidic chips using spin coating technology

Nowadays, the research and production of microfluidic chips for various applications in bio/chemical fields are attracting significant attention from scientists around the world. The fabrication of microfluidic chips typically involves two steps: creating open microchannels and subsequently sealing them. The sealing of these open microchannels is a critical step that determines the ultimate quality of the product. Adhesive bonding and solvent bonding are two commonly used approaches for sealing open channels. Both approaches require the creation of an adhesive layer or a solvent layer sandwiched between the two substrate surfaces to facilitate bonding under the influence of chemical and physical reactions. Therefore, controlling the process of creating this layer plays a vital role. To achieve this, spin coating is a technique often used to quickly and simply create thin coating layers owing to the centrifugal force. However, this method also has many limitations such as limited thickness control, uniformity issues, limited material compatibility, and limited control over film structure. In this study, the authors conducted an investigation of the factors affecting the formation of coating layers using the spin coating technique. The investigation results showed difficulties in choosing the substrate placement position and selecting the appropriate spinning speed for the coating material. Additionally, the authors propose the incorporation of a new force, in conjunction with centrifugal force, during the coating process, which demonstrates potential in mitigating the formation of distinctive thickness profiles by reducing the thickness in the central region of the coating