Bonding Technologies for PDMS Chips

Microfluidic devices have gained significant attention in the field of biological and medical research due to their potential for precise control and manipulation of small volumes of fluids. Among the materials used for microfluidic devices, PDMS is a popular choice due to its desirable properties such as biocompatibility, transparency, and ease of fabrication. However, bonding PDMS to itself or other substrates could be challenging due to its hydrophobic nature. To address this issue, various bonding technologies have been developed for PDMS, which are the focus of this article.

Bonding Technologies

• Oxygen Plasma Treatment

Oxygen plasma treatment is a widely used technology for bonding PDMS due to its simplicity and effectiveness. The process involves exposing the PDMS surface to oxygen plasma generated by a plasma cleaner, which creates oxygen-containing functional groups on the surface that enhance adhesion. Oxygen plasma treatment has been shown to improve the bonding strength and wettability of PDMS.

• Chemical Bonding

Chemical bonding involves introducing chemical agents, such as silane or adhesive, on the PDMS surface to create covalent bonds between adjacent surfaces. Silane coupling agents are commonly used for PDMS bonding, which act as a bridge between the PDMS surface and the substrate. Chemical bonding provides a strong and stable bond between PDMS and other substrates, and it has been successfully applied in various microfluidic applications.

• Ultraviolet/Ozone Treatment

Ultraviolet/Ozone (UVO) treatment is a surface modification technology that generates ozone and short-wave ultraviolet radiation to create active sites on the PDMS surface. The active sites react with oxygen to form hydrophilic groups, which enhance adhesion and wettability. UVO treatment has been shown to improve the bonding strength of PDMS to various substrates, including glass and silicon.

• Hot Pressure Bonding

The PDMS microfluidic chip is directly bonded to the substrate or another PDMS chip under high temperature and pressure. This method is simple and easy, but it requires that the surface of the chip is smooth, there can be no bulge or depression, and it is necessary to master the factors such as temperature, time and pressure to avoid the deformation or leakage of the microfluidic chip.

• Electric Polarization Method

The electric field is used to polarize the surface of the PDMS chip to make its surface with a positive or negative charge, resulting in electrostatic force to bond it with the substrate. This method requires high voltage and electric field, and attention should be paid to avoid the danger of arc discharge during operation.

To sum up, there are many kinds of bonding techniques for PDMS microfluidic chips, which need to be selected according to the actual situation.

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