Session: 14-02-01: General Topics in MEMS and Fabrication

Paper Number: 173737

Integration of a Modular, Mixed-Scale Fluidic System With a Fluidic Motherboard and Modules by Gasketless Superhydrophobic Fluidic Interconnects 

While monolithic integration offers a compact solution well-suited for lab-on-a-chip applications, hybrid integration, particularly through modular platforms that combine a fluidic motherboard with interchangeable processing modules, offers significant advantages. These include enhanced flexibility in material selection and the ability to independently optimize both manufacturing processes and biochemical workflows. Previous implementations of modular fluidic systems include a genosensor for tuberculosis detection and a system modularity chip for liquid biopsy of circulating tumor cells, both utilizing flexible tubes for fluid interconnects. More recently, gasketless superhydrophobic fluid interconnects (GSFIs) have enabled robust integration of modules onto mini-motherboards, with superhydrophobic coatings and magnet-assisted assembly ensuring leakage-free, gasketless sealing. This work presents the design, fabrication, and initial evaluation of a simplified, large-area fluidic motherboard integrated with test module chips using GSFIs.

As part of a rapid prototyping effort to demonstrate the feasibility of GSFIs for integrating a large-area fluidic motherboard with modules, the original two-layer motherboard design was simplified into a single-layer format compatible with double-sided direct milling on thermoplastics using a desktop CNC mill. The revised motherboard design incorporates microchannels, fluidic ports, and reservoirs on one side, while the opposite side includes magnet receiving ports, matching fluidic interconnects, and hemispherical alignment recesses. Test module chips were designed in the same footprint of functional modules, such as those for cell capture, solid-phase extraction and reverse transcription. These test modules feature serpentine microchannels on one side and magnet receiving ports, fluidic interconnects, and hemispherical-tipped posts on the other. Three sets of mating hemispherical cavities and posts provide passive alignment, enabling precise mechanical alignment and secure assembly through magnetic coupling.

The double-sided direct milling of the simplified motherboards and test module chips was performed using a Nomad 3 desktop CNC mill. Precise alignment between the two sides of the poly(methyl methacrylate) (PMMA) sheets was achieved using machined reference cavities and precision alignment pins. Upon completion of milling, all milled polymer parts were inspected under a microscope to verify dimensional accuracy and ensure thorough removal of polymer burrs. A subsequent cleaning protocol was applied, followed by a 12-hour oven drying process to prepare the polymer parts for bonding. Thermal fusion bonding with thin PMMA cover sheets was then conducted in a convection oven at 108 °C for 2 hours, resulting in fully sealed fluidic motherboards and test module chips.

Ongoing efforts involve inserting magnets into the designated magnet receiving ports and applying superhydrophobic coatings composed of dual-sized nanoparticles to establish GSFIs. Final assembly of the modules onto the motherboard will utilize passive alignment features in conjunction with magnetic coupling. Fluidic performance will be evaluated through syringe-driven flow experiments, with leakage pressure thresholds measured using an in-line pressure transducer.

This study represents a foundational effort toward establishing a modular microfluidic platform leveraging GSFIs. Future work will integrate task-specific biochemical processing modules with two-layer fluidic motherboards fabricated via polymer molding. Ultimately, the system will be used to conduct molecular assays involving cells and proteins, demonstrating the performance and practical utility of GSFIs in mixed-scale fluidic systems.

Presenting Author: Daniel Park Louisiana State University

Presenting Author Biography: Daniel S. Park received his Ph. D. degree in Electrical Engineering from the University of Texas at Dallas in 2004. He is currently a research associate at the Mechanical and Industrial Engineering and the Center for BioModular Multi-scale Systems (CBMM) in Louisiana State University, working on BioMEMS devices/systems for biomedical applications. His research interests include micro/nano fabrication techniques and their applications to BioMEMS and nano-scale devices/systems.

Authors:

Daniel Park Louisiana State University
Mohammad Derikvand Louisiana State University
Sunggook Park Louisiana State University
Steven Soper University of Kansas