Session: 03-01-03: Annual Conference-Wide Symposium on Additive Manufacturing

Paper Number: 150536

150536 - Binder Jet Printing Meets Liquid-Phase Sintering: Microfluidic Device Manufacturing 

Serpentine microchannels, essential in microfluidic circuits, mixers, separation columns, and heat exchangers, enable dense packing on planar substrates, increasing surface area for reactions and heat/mass transfer. Despite these advantages, such designs often result in higher pressure drops and increased pumping power. To address such issue, channels can be deepened to effectively enlarging the hydraulic diameter while maintaining dense packing. Silicon-based high-aspect-ratio microchannels have been produced by anodically bonding deep reactive ion etched silicon with glass, but this technique is limited to silicon and not applicable to common microfluidics materials like glass and PDMS due to the lack of suitable fabrication methods. Meantime, metallic serpentine microchannels are uncommon because traditional subtractive machining methods are slow and lack fine spatial resolution. Additive manufacturing (AM) offers new possibilities for creating intricate metal parts including enclosed internal features. Various AM techniques, including selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), and binder jet printing (BJP), have gained attention for fabricating metallic microfluidic devices including conformal cooling channels, heat exchangers, microreactors, and micro gas chromatography systems. The minimum dimension of these channels depends on not only the printing resolution, but the effectiveness of trapped powder removal strategies. In SLS, SLM, and EBM, high-pressure jets can remove loose powder, but this approach becomes less effective for smaller and longer channels. Thus, 3D-printed metallic serpentine channels typically feature open structures or sealed vent ports. BJP faces greater challenges as the as-printed parts are too weak to withstand high-pressure jets.

To address these limitations, we introduce an innovative method for fabricating long, high-aspect-ratio serpentine submillimeter channels in stainless steel (SS) using BJP and liquid-phase sintering (LPS). Instead of creating a single-part microfluidic component, we propose printing separate parts and joining them post-sintering. This approach allows for easy powder removal before final assembly. The separation of printing and sintering steps in BJP enables the joining of multiple parts during sintering, achieving near full-density and eliminating the need for additional steps required in SLS, SLM, or EBM. A critical innovation in our process is the addition of sintering additives, such as boron compounds, to the SS powder. These additives form a liquid phase at lower temperatures, facilitating bonding and consolidation. To demonstrate the feasibility of our approach, we have fabricated a 400-mm-long, fully enclosed serpentine channel with a rectangular cross-section of 0.5 mm width and 1.8 mm height. We have investigated how variations in sintering temperature and duration affect joining quality, interfacial strength, and channel geometry. The quality of the joins has been assessed through mechanical tests, electron microscopy, and micro-CT scans. Finally, we have measured the pressure drop across the channel and compared it to standard gas flow models to confirm the device’s performance and integrity. This novel method addresses the challenges of powder removal and enables the design of complex metallic microfluidic devices with high precision and structural integrity.

Presenting Author: Junghoon Yeom US Naval Research Laboratory

Presenting Author Biography: Dr. Yeom is a principal research engineer in Multifunctional Materials Branch at Naval Research Laboratory, where he has led multiple basic and applied research programs in the areas of nanomaterials, sensors/actuator, fracture and adhesion, manufacturing, and USMC vehicle programs. He completed his Ph.D. in Mechanical Engineering at the University of Illinois, Urbana-Champaign in 2007. He has more than 20 years of R&D experience in materials, microfabrication, heat transfer/fluid analysis, and sensors. Technical focus areas include mechanical testing at micro- and nanoscale, shock/vib testing and analysis, material synthesis and characterization, heat transfer analysis, chemical and pressure sensor developments, and additive manufacturing. Prior to joining in NRL, he was an assistant professor in the Department of Mechanical Engineering at Michigan State University, jointly leading efforts to develop 3D-printed temperature sensors, multifunctional soft micromotors for pollutant degradation, and novel nanopatterning techniques. He also served as a lead PI in a start-up company with NASA-sponsored R&D programs that developed miniature gas chromatography systems. He has coauthored a graduate textbook, Nanofluidics and Microfluidics, and published more than 80 peer-reviewed journal articles and conference proceedings.

Authors:

Junghoon Yeom US Naval Research Laboratory
Truong Do VinUniversity
Tyler Bauder US Naval Research Laboratory
Christopher Rudolf US Naval Research Laboratory
Patrick Kwon Michigan State University