S28 - Development of an Acoustically Transparent Microfluidics Device with a Soft Tissue Mimicking Substrate

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Jack Glennon

Undergraduate Researcher
Bucknell University
Erie, Pennsylvania, United States

Co-Author(s)

JZ

James Zhang

High School Student Researcher
Bucknell University, Pennsylvania, United States

Primary Investigator(s)

Olivia Boerman

Assistant Professor of Biomedical Engineering
Bucknell University
Lewisburg, Pennsylvania, United States

Introduction: : Chronic wounds are a major strain on the healthcare system affecting 6 million people in the U.S. alone. [1] Chronic wounds negatively impact the quality of life of those who have them especially because current treatments revolve around treating the wounds, not affecting the underlying reasons that are keeping the wounds from progressing with the healing process. [2] In a pilot clinical trial, it was shown that low intensity pulsed ultrasound (LIPUS) advanced chronic wound healing. [3] It is imperative that the mechanism of this wound healing is studied so that LIPUS treatments of chronic wounds can be improved and potentially used to treat other diseases. In order to understand how LIPUS affects blood vessels, which play a vital role in wound healing, a more accurate model of blood vessels both in healthy tissues and in chronic wounds must be developed. One important parameter missing from most advanced tissue models is blood flow. Chronic wounds, especially those caused by diabetes are characterized by low blood flow and consequently low shear stress. By using a gelatin substrate with a similar elastic modulus to blood vessels (100 kPa) with a cylindrical channel supported by a 3D printed resin structure, we hope to study how the combination of shear stress and LIPUS impacts endothelial cell behavior. The goal of this project was to develop a cylindrical microfluidic device for acoustic cell experiments accounting for reflections to model a more physiologically relevant wound environment.

Materials and

Methods: : A cytotoxicity assay was conducted with human umbilical vein endothelial cells (HUVEC) cells and ANYCUBIC clear resin to ensure biocompatibility according to ISO 10993 (Fig. 1). The resin parts were 3D printed using clear resin on ANYCUBIC Photon Mono X. The printed parts were washed in 70% isopropyl alcohol (IPA) in a Formlabs Form Wash for 5 minutes and then washed by hand in 99% IPA. The parts were cured in an Elegoo Mercury Plus 2.0 for 15 minutes. Next, 30 grams of Smooth-On Ecoflex 00-30 parts were mixed and placed in a vacuum for 15 minutes. The resin mold (Fig. 2A) was placed on a petri dish covered with tinfoil and vacuumed. The silicon mix was poured onto the mold and vacuumed for 15 minutes then cured overnight before being heated at 80°C for 4 hours (Fig. 2B). The resin substrate was placed into the silicone mold and 15% w/w gelatin was pipetted into the indent and cured at 4°C for 2 hours. 0.2% glutaraldehyde was pipetted onto the semicircular channel and incubated for 3 hours. (Fig. 2C) A series of PBS washes were performed and the substrate was resterilized with UV. 200 uL of 3.5 x 10^5 alive cells/mL human umbilical vein endothelial cells were placed on the semicircular channels of the gelatin substrate and incubated for 4 hours. After a confluent monolayer was formed, the substrates were dyed with FITC and DAPI (Fig. 2D, 2E).

Results, Conclusions, and Discussions:: Here, we demonstrate a viable cylindrical microfluidic device for acoustic exposure. After performing a cytotoxicity assay, the shape index (SI) of endothelial cells was found using ImageJ. A low SI meant that a cell was not circular, and thus viable. Group D, which was grown with a resin sample, was shown to be significantly different from the positive cytotoxic control group, but not significantly different from the negative control and no material groups (Fig. 1). Cells were shown to grow on the semicircular channels of the gelatin substrates (Fig. 2D,2E). We show that gelatin substrates and silicon molds were successfully manufactured without bubbles in the flow chamber (Fig. 2B) Fluorescent and brightfield imaging demonstrated that cells seeded onto the gelatin substrates (Fig. 2D,2E), enabling experiments to determine the behavior of endothelial cells after being subject to various shear stresses and ultrasound intensities. So far, the device has been shown to support cells and cell imaging, both in fluorescence and brightfield (Fig. 2D,2E). Though the acoustic impedance of the gelatin and resin have not been found, calculations using the acoustic impedance of similar materials suggests that there will not be issues with LIPUS transmission. [4,5] This proof of concept prototype shows, to the author’s knowledge, the first microfluidic device that is acoustically transparent for low ultrasound frequencies, enabling low ultrasound reflections for cell studies. Future works include finalizing a robust and reproducibly manufactured microfluidic device that will be used for ultrasound and shear studies. This microfluidic device will provide a more physiologically relevant environment to enhance ultrasound technologies for improved healing.

Acknowledgements and/or References (Optional): : References
[1] Guo, S, and L A Dipietro. “Factors affecting wound healing.” Journal of dental research
vol. 89,3 (2010): 219-29. doi:10.1177/0022034509359125
[2] Han, G., & Ceilley, R. (2017). Chronic Wound Healing: A Review of Current
Management and Treatments. Advances in therapy, 34(3), 599–610. https://doi.org/10.1007/s12325-017-0478-y
[3] Gibbons GW, Orgill DP, Serena TE, Novoung A, O’Connell J,B, Li WW, & Driver VR
(2015). A prospective, randomized, controlled trial comparing the effects of noncontact, low-frequency ultrasound to standard care in healing venous leg ulcers. Ostomy/wound Management, 61(1), 16–29.
[4] Palanisamy, R. P., Chavez, L. A., Castro, R., & Findikoglu, A. T. (2024). Void-Engineered
Metamaterial Delay Line with Built-In Impedance Matching for Ultrasonic Applications. Sensors (Basel, Switzerland), 24(3), 995. https://doi.org/10.3390/s24030995
[5] Peiran Chen, Andreas M.A.O. Pollet, Anastasiia Panfilova, Meiyi Zhou, Simona Turco,
Jaap M.J. den Toonder, Massimo Mischi, Acoustic characterization of tissue-mimicking materials for ultrasound perfusion imaging research, Ultrasound in Medicine & Biology, Volume 48, Issue 1, 2022, Pages 124-142, ISSN 0301-5629, https://doi.org/10.1016/j.ultrasmedbio.2021.09.004.