Pressure-Free Assembling of Poly(methyl methacrylate) Microdevices via Microwave-Assisted Solvent Bonding and Its Biomedical Applications

Abstract

Poly(methyl methacrylate) (PMMA) has become an appealing material for manufacturing microfluidic chips, particularly for biomedical applications, because of its transparency and biocompatibility, making the development of an appropriate bonding strategy critical. In our research, we used acetic acid as a solvent to create a pressure-free assembly of PMMA microdevices. The acetic acid applied between the PMMA slabs was activated by microwave using a household microwave oven to tightly merge the substrates without external pressure such as clamps. The bonding performance was tested and a superior bond strength of 14.95 ± 0.77 MPa was achieved when 70% acetic acid was used. Over a long period, the assembled PMMA device with microchannels did not show any leakage. PMMA microdevices were also built as a serpentine 2D passive micromixer and cell culture platform to demonstrate their applicability. The results demonstrated that the bonding scheme allows for the easy assembly of PMMAs with a low risk of clogging and is highly biocompatible. This method provides for a simple but robust assembly of PMMA microdevices in a short time without requiring expensive instruments.

Bonding Strategies for Thermoplastics Applicable for Bioanalysis and Diagnostics

“…The process is fast and inexpensive. Notably, high bond strength of 11.75 and 14.95 MPa can be achieved when applying acetic acid for microwave-assisted or UV-assisted solvent bonding of PMMA microdevices, respectively [59,60]. These bonding strengths are higher than the limits of typical thermal and adhesive bonding.…”

“…Different types of solvents can be applied for thermoplastic bonding depending on thermoplastic materials. For example, PMMA devices can be bonded using ethanol [61,62], chloroform [63], isopropyl alcohol [64], and acetic acid [36,59,60], while cyclic olefin polymer (COP) sealing can be performed using cyclohexane and toluene [65].…”

“…These bonded microdevices were successfully applied for culturing human cells such as human umbilical vein endothelial cells (HUVECs) and mesenchymal stromal cells (MSCs). This has provided good alternative platforms to perform on-chip viability assays [33,59,60]. Young et al described the fabrication of PS microfluidic devices (hot embossing replication and thermal bonding) for two different cell-based applications including HUVECs activation and neutrophil chemotaxis [28].…”

Advanced Materials and Sensors for Microphysiological Systems: Focus on Electronic and Electrooptical Interfaces

“…As a final caveat, the inherent gas permeability of PDMS limits the possibility of regulating O 2 and CO 2 tension and water evaporation in the device. Other materials used for the creation of MPS include polymethyl methacrylate (PMMA), [ 25,172 ] polycarbonate, [ 26 ] off‐stoichiometry thiol–ene (OSTE), [ 27 ] and glass. [ 28 ] While they offer benefits like reduced drug adsorption, [ 29 ] they demand fabrication methods with slower prototyping and more expensive equipment.…”

Recent Advances in Thermoplastic Microfluidic Bonding

“…The solvent was applied to two PMMA bonding surfaces and clamped using binder clips and placed in microwave for 90 s. Ethanol was found to be most effective for bonding of PMMA substrates, and channel clogging and distortion was reduced [ 64 ]. Microwave assisted bonding using acetic acid as solvent was also used to achieve uniform bonding and high bond-strength without using any external pressure while bonding PMMA substrates [ 65 ]. Ng et al developed a bonding technique to prevent excessive channel clogging and distortion, in which the PMMA substrates were bonded by isopropanol combined with the pre-processing step of pressure and thermal annealing of the PMMA substrates, and a post-processing step of solvent removal by subjecting the chip to a vacuum environment.…”