Polydimethylsiloxane (PDMS), because of its good mechanical properties, optical properties and chemical stability, and easy to process molding, low price, has increasingly become the preferred material for the preparation of microfluidic chips. However, because PDMS itself is a highly hydrophobic, porous material. In the process of sample separation, especially for biomolecules, serious tailing phenomenon is easy to occur due to adsorption, which may ultimately lead to separation failure, seriously limiting the application of PDMS in the field of microfluidic chips. Therefore, the hydrophilic modification of PDMS surface to inhibit the adsorption of the separation is particularly important.

At present, the surface modification methods of PDMS are mainly divided into physical methods and chemical methods. The physical methods include Plasma, uv and ozone radiation. Chemical methods include surfactant treatment and graft copolymerization.

Physical methods

Physical method mainly through physical technology to PDMS surface group oxidation, crosslinking and other effects, change the surface chemical structure, improve hydrophilicity.

Plasma treatment

Plasma is an ionized gaseous substance composed of the atoms that have been stripped of some electrons and the positive and negative electrons produced after the atoms are ionized. Plasma is mainly divided into high temperature plasma and low temperature plasma. Among them, low temperature plasmas can be produced in laboratory environments, especially oxygen plasmas. The hydrophobic silicon methyl group on the surface of PDMS can be transformed into hydrophilic groups such as silicon hydroxyl group by plasma, which is widely used in the sealing and surface modification of PDMS microfluidic chips.

Chemical methods

Surfactant treatment

Surfactants are substances that can significantly reduce surface tension at very low concentrations, and their molecules are composed of hydrophilic and hydrophobic groups located at both ends of the molecule. The hydrophobic group of the surfactant is connected to the surface of THE PDMS, so that the hydrophilic group is on the outside, improving the hydrophilicity of the entire PMDS surface. The surfactants used for surface modification of PDMS are mainly divided into anionic, cationic, non-ionic and special types, among which sodium dodecyl sulfate (SDS) is the most commonly used surface modifier of PDMS.