Network-expandable polydimethylsiloxane for cost-free enhanced droplet yield and smart temperature control in microfluidics

Hydrophilic surface modification of polydimethylsiloxane (PDMS) during bonding compromises environmental robustness and aqueous phase manipulation in microfluidics. This study proposes a strategy of incorporating mono-vinyl-terminated PDMS (MVT-PDMS) for controlled network expansion to fabricate a new biocompatible organosilicon (VPDMS) for microfluidic devices. VPDMS can rapidly form a stable interfacial oil layer during droplet production which effectively blocks the contact between the aqueous droplets and the extremely hydrophilic surface to improve aqueous phase manipulation in microfluidics. Therefore, the surface of the VPDMS channel maintains an ultrahydrophobicity (water contact angle, WCA ∼ 171°) and environmental robustness during droplet production even after prolonged oxygen plasma treatment. The ultrahydrophobic channel facilitates the shearing of the aqueous phase by the oil phase, resulting in a maximum 150 % increase in droplet yield without changing two-phase flow rates, chip structure, or surface modification. The WCA-dominated droplet yield improvement achieves a maximum 400 % increase over the flow rate-dominated improvement. Furthermore, the VPDMS's sparse network and enhanced curing efficiency (502 %) improve the integration and anchoring of the nanomaterials in the VPDMS matrix. Taking nanomaterial MXene as an example, the VPDMS-MXene composite chip offers superior thermal regulation, surpassing traditional methods with programmable precision in temperature control and reducing thermal losses during chip temperature management. A bubble generator has been developed for local gas modulation by the composite chip. Overall this work develops a new organosilicon that directly increases droplet yield, nanomaterial loading, biocompatibility, and smart laser temperature control, enabling low energy and sustainable production of microfluidic droplets.