Enhanced Fabrication of Microdroplet Generator Nozzle Arrays: Optimizing KOH Etching for Microfluidic Applications

<p>Ultrasonic microdroplet generators are useful devices with broad applications ranging from aerosolized drug delivery to three-dimensional (3D) printing-based additive manufacturing. One such technology comprises a microfabricated array of nozzles with droplet production driven by a piezoelectric transducer. The present study focuses on refining a critical fabrication step, anisotropic wet etching of pyramidal nozzles using a basic potassium hydroxide (KOH) solution. Given the integral role of nozzle geometry in device operation, high-precision techniques including Reactive Ion Etching (RIE), Deep Reactive Ion Etching (DRIE), and KOH wet etching were employed. A tapering geometry is preferred for acoustic wave focusing and efficient droplet generation, and KOH etching naturally yields pyramids due to preferential removal of the (100) plane versus the (111) plane of single-crystal silicon. Though wet etching is less precise than dry etching, it is difficult to form these 3D shapes using dry etching alone. Thus, this work focused on realizing the highest possible level of control over KOH etching. Challenges were encountered in using a conventional etching setup to achieve uniform etching and good surface smoothness, which are crucial to definition of the pyramidal tip geometry. These aspects are also important for use of KOH etching to define microstructures in a range of microfluidic systems. Here, we introduce an ultrasonic-assisted etching method to enhance the KOH etching process, addressing issues like non-uniform etching rates and surface roughness. This research not only provides insight into the microfabrication of ultrasonic microdroplet generators but also contributes to further improvements in microfluidic device manufacturing.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering & Materials Science

Year dc:date.available

2023

Author dc:creator

• Bai, Hongyu

Contributors dc:contributor

• John Mark Meacham
• Patricia Weisensee Xianglin Li

• Microfabrication
• Etching
• Chemical elements
• Microfluidics
• Engineering
• Mechanical Engineering

Statement dc:rights

• I have not registered my thesis with the U.S. Copyright Office, and do not intend to.

Language dc:language

English (en)

Identifier

https://openscholarship.wustl.edu/eng_etds/986

OAI identifier oai:identifier

oai:openscholarship.wustl.edu:eng_etds-2017