Comparison of PDMS and NOA Microfluidic Chips: Deformation, Roughness, Hydrophilicity and Flow Performance

Area of Science:

• Materials Science
• Microfluidics Engineering
• Fluid Dynamics

Background:

• Polydimethylsiloxane (PDMS) is a common microfluidic material but its compliance causes channel deformation under pressure.
• This deformation leads to increased response times and experimental inefficiencies, particularly with syringe pumps.
• Norland Optical Adhesive (NOA) offers potential advantages due to its rigidity and optical properties.

Purpose of the Study:

• To compare the compliance and deformation of microfluidic devices fabricated from PDMS and NOA.
• To evaluate material properties including Young's modulus, roughness, contact angle, and flow resistance.
• To assess the suitability of NOA as an alternative to PDMS in microfluidic applications.

Main Methods:

• Fabrication of microfluidic devices with characteristic channel widths (100, 40, and 20 µm) using PDMS and NOA.
• Measurement of Young's modulus, surface roughness, and contact angle for both materials.
• Estimation of experimental flow resistance using pressure and flow rate measurements.
• Characterization of system response time using a two-element resistance-compliance (RC) hydraulic circuit model.

Main Results:

• NOA exhibited a significantly higher Young's modulus (1743 MPa) compared to PDMS (2 MPa).
• NOA microfluidic devices demonstrated lower compliance and channel width deformation than PDMS devices.
• Surface roughness was higher in NOA compared to PDMS, while hydrophilicity was comparable after plasma treatment.

Conclusions:

• NOA microfluidic devices show reduced compliance and deformation, leading to faster response times compared to PDMS.
• The increased rigidity of NOA makes it a promising material for microfluidic applications requiring high precision and efficiency.
• NOA offers a viable alternative to PDMS for fabricating microfluidic devices, potentially improving experimental throughput.