A surface-modified sperm sorting device with long-term stability

Microfluidic devices fabricated from poly (dime- thylsiloxane) (PDMS) offer the ability to improve our biological and medical capabilities. Although PDMS offers a range of intriguing benefits for biomedical applications, the intrinsically hydrophobic nature of PDMS may impede with the tremendous potential of these devices. Here, we describe a PDMS-based sperm sorting device, which has been surface-modified via graft-co-polymerization of poly(ethylene glycol) methyl ether methacrylate to create a moderately hydrophilic and non-fouling surface. This process involves the exposure of PDMS to UV/ozone, which activates the PDMS surface to bond to the substrate and, at the same time, initiates the graft-co-polymerization from the PDMS surface. In this study, we confirmed long-term stability of surface-modified PDMS for up to 56 days based on Fourier transformation infrared spectroscopy (FTIR), contact angle measurements, and protein adsorption studies. Moreover, the applicability of our method to PDMS-based sperm sorting devices was demonstrated by successfully sorting human sperm.