Y2 - Enabling Models of Pathologically High Shear Stress Using a Simple, Versatile and, Reversible Bonding Technique for 3D-Printed Microfluidics

Friday, October 10, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Priscilla Delgado, MS

PhD Candidate
Georgia Tech and Emory University
Atlanta, Georgia, United States

Co-Author(s)

RI

Rizky Ilhamsyah

PhD Candidate
Georgia Institute of Technology, United States
MT

Martin Tomov

Core Director I
Emory University, United States

Primary Investigator(s)

David Myers

assistant professor
Emory, United States

Introduction: : 3D-printed microfluidics offer the ability to rapidly integrate complex topologies that are difficult to fabricate using traditional lithography methods. However, a perennial challenge lies in joining 3D-printed microfluidics to dissimilar surfaces such as coverslips for high resolution imaging, embedding sensors, or polystyrene to support cell culture. To that end, we introduce a new bonding technique that is surprisingly much stronger than traditional PDMS-glass bonding yet reversible. In our approach, the 3D-printed microfluidic and dissimilar substrate are held together while UV-cured glue is injected into a separate microfluidic channel that was created along the perimeter of the device. After a brief 1 min exposure to UV light, the UV cures, bonding the substrate to the microfluidic lid. While the bond is able to hold the device together under normal loading and pressure conditions, it is susceptible to mechanically applied shear, and therefore reversible.

We specifically tested our novel approach for use with a device designed to apply varying levels of shear stress to endothelial cells, as well as embedding a screen-printed electrode. Shear stress plays an integral role within the body impacting cell functionality in many physiological processes and disease states ranging from cardiovascular to cancerous. For example, low shear (0.4-4 dynes/cm^2) promotes atherosclerosis, while normal levels (10-70 dynes/cm^2) maintain vascular health, and high shear (>1000 dynes/cm^2) in stenotic arteries triggers platelet activation(1,2). Our new bonding technique addresses this issue and allowed us to achieve shear stresses that were 30x higher than with a PDMS/glass-based device with identical dimensions.

Materials and

Methods: : The microfluidic was designed in Solidworks, simulated in Autodesk CFD using flowrates from a range of 0-238 mL/min (equipment maximum) to obtain shear stress values, and 3D-printed in Biomed Clear Resin using a Form 3BL printer. The five zones within the channel were designed to gradually increase the shear at even increments on the sample of interest (Fig. 1A). To test biocompatibility, human umbilical vein endothelial cells (HUVECs) were cultured in the devices coated with fibronectin. The cells attached, proliferated, and spread evenly within the channels under low flow (shear stress: 0.003 dynes/cm^2) conditions overnight before shear stress testing was performed at 15.1 dynes/cm^2 to observe cell alignment. Fixed staining for cell nucleus and membrane was performed. Autofluorescence from resin is observed at wavelengths for DAPI (488 nm), for live imaging alternative stains can be utilized to reduce this. If using DAPI with fixed staining, the microfluidic can be easily removed to avoid autofluorescence interference. The UV cure glue can be easily peeled off of the microfluidic and the device can be sterilized for reusability. A gold screen-printed electrode was embedded within the microfluidic and chronoamperometric measurements of ferricyanide reduction and oxidation were taken from flowrates 0-238 mL/min.

Results, Conclusions, and Discussions:: Experimentally, the equipment maximum achieved shear stress within the device was 1137 dynes/cm^2 when bonded to glass coverslips, coated polymer coverslips, and polystyrene petri dishes without breaking. Comparatively, a PDMS plasma bonded to glass device with identical dimensions was able to withstand an average maximum shear stress of 31.36 dynes/cm^2 before bursting. When comparing shear stress growing conditions for cells, the HUVECs transitioned from a cobblestone shape to an elongated shape as the shear increased which was reflected with the angle of alignment of the cell going from scattered to primarily within the 0-90˚ range (Fig. 1B). Upon embedding a screen-printed electrode, chronoamperometric measurements of ferricyanide revealed a 10-fold increase in sensitivity from an increase in flow of 0-238 mL/min (Fig. 1C).

This highly adaptable, biocompatible, reversibly bonded microfluidic platform offers bonding strengths that rival those of comparable PDMS bonded devices. This system not only simplifies prior fabrication processes through the accessibility of 3D-printing, but facilitates high-resolution imaging, in turn paving the way for future studies on the effects of pathological shear stress and high shear electrode measurements.

Acknowledgements and/or References (Optional): : Acknowledgements:
This project received financial support from the Atlanta Network for Training in KUH Scientific Research (ATLANTIS) grant from the National Institute of Diabetes, Digestive, and Kidney Diseases (TL1DK136047).

References:
(1) Cunningham, K. S., & Gotlieb, A. I. (2005). The role of shear stress in the pathogenesis of atherosclerosis. Laboratory Investigation; a Journal of Technical Methods and Pathology, 85(1), 9–23. https://doi.org/10.1038/labinvest.3700215
(2) Kanda, H., Yamakuchi, M., Matsumoto, K., Mukaihara, K., Shigehisa, Y., Tachioka, S., Okawa, M., Takenouchi, K., Oyama, Y., Hashiguchi, T., & Imoto, Y. (2021). Dynamic changes in platelets caused by shear stress in aortic valve stenosis. Clinical Hemorheology and Microcirculation, 77(1), 71–81. https://doi.org/10.3233/CH-200928