Surface Modification Analysis of the Closed Containers that are used in Plasma Treatments of Food, Agriculture, and Biomedical Samples

Plasma treatments inside closed containers is ideal for food, agriculture, and biomedical samples to mitigate post-process contamination. Typical containers are plastic bags that are made out of low-density polyethylene (LDPE), polyethylene terephthalate (PET), nylon, and Teflon FEP polymers. The transparent heat-sealable bags offer an easy solution for plasma treatment of delicate samples. However, the issue of polymer degradation and interference with the sample processing has to be addressed. An alternative plasma apparatus is discussed that allows plasma treatments inside sealed glass vials.

FTIR and Raman spectroscopy show increased oxygen functional groups, which make LDPE, PET, and nylon surfaces more hydrophilic. A recovery in contact angle was observed within 5 days of 1 minute air plasma treatment. Longer treatment time leads to permanent surface functionalization in LDPE and nylon, showing no recovery in contact angle. Depletion of fluorine species was observed in plasma treated Teflon FEP. This leads to enhanced hydrophilicity and no recovery was observed in the contact angle. Some of the depleted fluorine species get attached to the treated sample, shown in the XPS analysis. Plasma treatment inside glass vials show trace amounts of sodium on the treated sample.