One-step bonding and hydrophobic surface modification method for rapid fabrication of polycarbonate-based droplet microfluidic chips

Abstract

Chip bonding and hydrophobic surface modification are two critical processes for the fabrication of a droplet microfluidic chip from the thermoplastic polycarbonate (PC) material. In this paper, we describe a novel one-step method, which simultaneously bonded and modified two PC substrates. The mechanism of this one-step method is that n-pentane acts as a sacrificial solvent and acetone is the solvent that bonds the PC substrates. Additionally, entrapment functionalization and the Si-O-Si cross-linked network play a central role in the hydrophobic surface modification process. The method was optimized to achieve a high bonding strength, low surface roughness, and high optical transmittance. The naturally hydrophilic PC substrate surface was modified to become a hydrophobic surface, with surface tension decreased from 33.6 mN/m to 14.8 mN/m. Monodisperse droplets generated using a droplet generation chip fabricated by this method had an average diameter of 101.3 μm and coefficient of variation of 0.55%. A droplet digital polymerase chain reaction experiment was successfully carried out using droplets generated from this chip, which demonstrated the effectiveness of this method. This novel one-step method holds great potential for manufacturing droplet-based microfluidic chips using PC in large-scale, and it may have broad applications in microfluidic research fields.