On the Effects of 3D Printed Mold Material, Curing Temperature, and Duration on Polydimethylsiloxane (PDMS) Curing Characteristics for Lab-on-a-Chip Applications

Abstract

Soft lithography with microfabricated molds is a widely used manufacturing method. Recent advancements in 3D printing technologies have enabled microscale feature resolution, providing a promising alternative for mold fabrication. It is well established that the curing of PDMS is influenced by parameters such as temperature, time, and curing agent ratio. This study was conducted to address inconsistencies in PDMS curing observed when using different 3D-printed mold materials during the development of a Lab-on-a-Chip (LoC) system, which is typically employed for investigating the effect of hydrodynamic cavitation on blood clot disintegration. To evaluate the impact of mold material on PDMS curing behavior, PDMS was cast into molds made from polylactic acid (PLA), polyethylene terephthalate (PET), resin, and aluminum, and cured at controlled temperatures (55, 65, and 75 °C) for various durations (2, 6, and 12 h). Curing performance was assessed using Soxhlet extraction, Young's modulus calculations derived from Atomic Force Microscopy (AFM), and complementary characterization methods. The results indicate that the mold material significantly affects PDMS curing kinetics due to differences in thermal conductivity and surface interactions. Notably, at 65 °C, PDMS cured in aluminum molds had a higher Young's modulus (~1.84 MPa) compared to PLA (~1.23 MPa) and PET (~1.17 MPa), demonstrating that the mold material can be leveraged to tailor the mechanical properties. These effects were especially pronounced at lower curing temperatures, where PLA and PET molds offered better control over PDMS elasticity, making them suitable for applications requiring flexible LoC devices. Based on these findings, 3D-printed PLA molds show strong potential for PDMS-based microdevice fabrication.

Keywords: 3D printing; PDMS curing; Young’s modulus of elasticity; microfluidic devices; organ-on-a-chip.

Figure 1

(a) Design of small-scale PDMS mold used in this study; (b) Representative design of a Lab on a Chip Device; (c) Real image of a LoC PDMS device; (d) Real images of molds fabricated with different materials.

Figure 2

Experimental Setup: (A) Heat transfer experiment; (B) PDMS preparation and curing process.

Figure 3

Three-dimensional AFM images of mold surfaces in contact with PDMS (a) PLA, (b) PET, (c) Al, and (d) resin mold, respectively.

Figure 4

Young’s modulus elasticity of PDMS samples cured in different molds at different times and temperatures (a) at 55 °C, (b) at 65 °C and (c) at 75 °C.

Figure 5

Soxhlet analysis results for different curing times: (a) 2 h, (b) 6 h, and (c) 12 h.

Figure 6

Average surface temperature profiles of molds during PDMS curing at 75 °C, recorded over a 30-min interval.

Figure 7

TGA analysis of PDMS samples.

Figure 8

FTIR results of PDMS samples.

Figure 9

SEM images of PDMS samples cured with (a) PLA, (b) PET, (c) Al and (d) resin mold, respectively. Smooth surfaces of PDMS samples are highlighted in dashed squares.