Electrospinning, also known as electrospinning, is a technology that uses a high-voltage electrostatic field to stretch polymer droplets and refine them. The solvent evaporates and solidifies into fibers, which are then deposited onto a receiving device to form a polymer fiber membrane!. The electrospun film produced has the advantages of high porosity, large specific surface area, good flexibility, and easy surface modification, and has attracted widespread attention in fields such as environmental purification, biomedicine, and wearable devices; However, the surface of electrospun films lacks sufficient active sites and requires surface modification to obtain multifunctional films with additional properties to broaden their application scenarios. Surface modification of electrospun films can be divided into chemical modification and physical modification. Physical modification mainly includes immersion coating method, magnetron sputtering method, plasma treatment method, heat treatment method, and polydopamine (PDA) adhesion method. Physical modification has become the first choice for surface modification of electrospun films due to its advantages of easy operation, no chemical by-products, and low dependence on surface functional groups. Polycaprolactone (PCL) has a high elastic modulus and excellent spinnability, making it very suitable for electrospinning technology processing. Electrospun PCL film has good thermal stability and biocompatibility, and has been applied in medical fields such as tissue engineering scaffolds and drug carriers; However, its low surface hydrophilicity is not conducive to cell attachment, migration, proliferation, and differentiation, hindering its deep application in the biomedical field. This article mainly introduces the plasma treatment technology of electrospun PCL thin film.

Plasma Treatment

Plasma treatment is a modification method for the surface of materials. In the reactor, glow discharge plasma is generated at low pressure and energy is obtained through electromagnetic radiation or AC/DC interactions. Charged substances in gas plasmas include ions, electrons, free radicals, metastable states, and photons. These active substances bombard the solid surface, transferring energy from the plasma to the solid surface and being etched by leaving many reaction sites, which can remove surface contamination, deposit thin coatings, and introduce new chemical functional groups. Proper selection of plasma sources and operating parameters can help form different functional groups on the surface of thin films (such as amino or carboxyl groups generated on the film surface by ammonia or oxygen plasma treatment, which can adjust the adhesion, roughness, and wetting properties of the film surface). Plasma treatment is fast and efficient, does not use any solvents, and does not produce chemical by-products, making it environmentally friendly.

Improve Biocompatibility

The surface of PCL film treated with plasma will generate various functional groups containing N or O, significantly increasing the adhesion and vitality of fibroblasts. In addition, PCL film treated with oxygen plasma has better biocompatibility, indicating that plasma modification technology has development prospects in the field of biological activation of polymer surfaces.

Improve Hydrophilicity

PCL is a hydrophobic polymer. In order to improve its surface hydrophilicity, PCL fiber membranes were treated with oxygen plasma under vacuum conditions using a plasma cleaning machine to enhance their hydrophilicity. As shown in Figure 1, the contact angle of PCL fiber membrane significantly decreased after oxygen plasma treatment. The contact angle of untreated PCL fiber membrane was about 120 ± 2.5 °, and the contact angle of treated PCL (plasma) fiber membrane was about 26 ± 1.8 °.

Figure 1 Contact angle test of PCL thin film before and after oxygen plasma treatment

In summary, plasma treatment can effectively enhance the hydrophilicity of PCL films, improve cell adhesion, proliferation, and migration abilities.