Femtosecond laser pulse inducing hydrophilicty and hydrophobicity on polycarbonate surfaces

Abstract

This study investigated the use of ultrashort femtosecond laser pulses to induce either hydrophilic or hydrophobic surfaces on polycarbonate (PC). It has been observed that controlled modification of wettability could be achieved over a wide range of the water contact angle from below 5° to above 150°. It has been shown that the pulse energy fluence and total energy deposition onto PC are the important factors in determining the laser–PC interaction and therefore the different level of wettability on PC surface. X-ray photoelectron spectroscopy-spectra measurement indicates that the modification was caused dominantly by laser induced chemical bond changes. The changes in surface morphology may not noticeably contribute to the surface wettability. The results would be useful in microfluidics chip design and fabrication with controlled surface wetting properties.