Surface Engineering Microfluidic Devices for Cardiovascular Applications Using Novel Plasma Surface Treatments

Abstract

Microfluidic devices are used in biological applications like organs-on-chips and biosensing through microchannels tailored for specific functions. Biomolecule immobilisation is crucial in microchannel surface engineering, usually done with toxic, costly methods such as oxygen plasma treatment and chemical linkers. This thesis explores innovative plasma surface treatments for biomolecule immobilisation in microfluidics, focusing on plasma-activated coating (PAC) and atmospheric pressure plasma jet (APPJ). These techniques create active chemical species on microchannel surfaces that enable direct, covalent attachment of biomolecules—like proteins and antibodies—eliminating linkers, enhancing stability, and reducing fabrication time and costs while avoiding toxic processes. Treatments were optimised for common microfluidic materials like PDMS and glass, improving the growth and function of vascular endothelial cells (ECs) and smooth muscle cells (SMCs). APPJ treatment also enabled irreversible bonding of PDMS and glass for durable devices. Microfluidic single-channel and co-culture blood vessel models on a chip were developed, surpassing traditional oxygen plasma treatments by effectively simulating EC elongation and SMC plasticity in vitro. A microfluidic device with patterned biomolecule channels and an organ-on-a-chip with a biomimetic hydrogel membrane was created to study SMC phenotypic plasticity and EC-SMC signalling.

Additionally, APPJ was evaluated for enhancing anti-thrombogenic properties of blood-contacting devices through whole-blood adhesion and thrombosis-on-a-chip studies. PDMS treated with APPJ showed improved anti-thrombogenic effects, likely due to its low stiffness and high wettability from APPJ treatment, reducing platelet and fibrin attachment even at low heparin concentrations. These plasma treatments open new pathways for enhancing microfluidic and biomedical devices for cardiovascular applications.