Control of microfluidics channel geometries using temperature-responsive hydrogel

• Main Author: Sim, Elton Ji Long
• Other Authors: Hou Han Wei
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Manufacturing::Polymers and plastics; Engineering::Chemical engineering::Biotechnology; Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/150674
• Institution: Nanyang Technological University

Spiral inertial microfluidics is a membrane-free technique for cells separation based on hydrodynamic forces. These devices typically require specific channel dimensions for different target cells separation, and laborious fabrication processes have to be repeated for optimization. Therefore, microfluidic devices with tunable channel dimensions would significantly reduce labor and cost as they can be controlled to cater for a larger size range of cell separation. This thesis proposes a novel fabrication method for tunable microfluidic devices using thermo-responsive Poly (N-isopropylacrylamide) (PNIPAM) hydrogel. By coating the hydrogel in a microchannel, the size of the hydrogel can be controlled via temperature to constrict the channel dimensions. Two hydrogel fabrication methods, namely, photolysis-based, and persulfate-based, was evaluated in terms of stability and volumetric response to temperature change of the hydrogel in two different microfluidic devices (Capillary Burst Valve (CBV) chip and straight microchannel). Results showed that a 100:1 monomer to crosslinker ratio through persulfate polymerization was optimal for a highly thermo-responsive and stable hydrogel that yielded ~44% volume change in both chips. Next, hydrogel coating process was performed via surface modification of microchannels with silanes and different microchannel geometries (straight and diagonal microchannels). Successful hydrogel coating was achieved via surface modification with vaporized Trichlorosilane in a 1_mm straight microchannel and a 5-channel chip without surface modification. For the latter, the hydrogel could sustain a flow rate of 10 mL/min at both swollen and unswollen condition. Taken together, the results demonstrated the promising potential of PNIPAM hydrogel as a novel method for tuning microfluidic device dimensions. These results provide opportunities for further optimization in hydrogel chemistry and surface coating of temperature-responsive hydrogel to enable fabrication of microfluidic devices with tunable dimensions.