Sponsored By

Medical Micromolding: Challenges and SolutionsMedical Micromolding: Challenges and Solutions

Associate professor of plastics engineering at UMass Lowell, Davide Masato shares insights on how material behavior is affected during the micromolding process.

Norbert Sparrow

January 22, 2025

4 Min Read
Masato quote about micro molding
Canva

Micromolding increasingly is being applied to medical manufacturing. The process enables the large-scale production of components with intricate geometries and high precision, which are essential for the functionality of advanced medical devices. The technique has its challenges, however, not the least of which is material behavior at the micro scale. Davide Masato, associate professor in the department of plastics engineering at the University of Massachusetts Lowell, will speak to these challenges — and how to overcome them — at MD&M West in Anaheim, CA, running from Feb. 4 to 6. His session, Design for Micro Injection Molding of Medical Devices, is scheduled for 3 PM on Feb. 4 at the event. In this interview with PlasticsToday, he shares some of the insights he will touch on during his presentation.

Let’s begin by defining micromolding. Obviously, part size is one parameter, but it’s not the only one, correct?

The most widely accepted definition relates to parts that are very, very small by volume or that have very small features on a larger geometry. On top of that, I find that industry defines micromolding not just as these two types of products, but also considers the manufacturing technology that is used to produce these parts — machines that are specifically designed for micro-tooling applications.

Related:Medtech Is in a Period of Chaotic Change. Here’s What Your Company Must Do to Succeed

molding-lab-UMass-Lowell.jpg

Is demand for micromolding growing in the medical manufacturing space? If so, what is driving this growth?

The data I've seen suggests that micromolding applications are definitely growing, especially in the medical sector. That includes everything from minimally invasive devices for surgical procedures to devices made with implantable materials and that may be bioresorbable, for example.

Bioresorbablility is an amazing technology, but it is not limited to micromolding, correct?

It is not limited to micromolding. Generally speaking, any material you would consider using in conventional injection molding is suitable for micromolding. The difference is that micromolding makes smaller devices that are better suited to fit into our bodies for surgical repairs or implants. However, the polymer material behavior at the micro scale must be considered during design and manufacturing.

Can you elaborate on how micromolding may affect material behavior?

The first thing to keep in mind is that cooling rates are much more aggressive in micromolding applications than they are in injection molding. In injection molding, the cooling time is proportional to the square of the wall thickness of the part. Hence, if you reduce the wall thickness for a micromolded part, the cooling rate increases significantly. The rapid material solidification can lead to different material behavior during flow. In particular, high shear rate and pressure drop are common for polymer flows in micromolding. These can lead to challenges with processing as well as changes in the molded part’s morphology.

There are other aspects to consider, as well. When you're filling something very small, some phenomena that are typically disregarded at the larger scale can become more important. High shear stresses, for example, could result in wall slip at the mold-polymer interface. Other phenomena to be considered can include inertial effects, capillary forces, and more.

Additives that promote melt flow or reduce cooling rates are used to facilitate processing and support product quality. In general, when it comes to micromolding, the higher the material’s melt flow rate, the easier it will be to replicate the mold cavity geometry.

I believe you will be looking closely at material flow during your presentation, right?

Yes, in particular, simulation can be used to predict flow at the micro scale. As I mentioned, there are some phenomena that are not necessarily modeled in commercial software, but that can be adjusted. There are certain parameters to look at when considering micromolding simulations. Additionally, I will touch on some strategies that we have explored in our research, such as functionalizing the surface of an injection mold to create better material flow inside small cavities.

What takeaways do you hope attendees come away with from your session?

My goal is to provide attendees with a better understanding of how simulation can be used in micromolding and how model parameters can be adjusted when you're dealing with micromolding. I also hope that people find inspiration in the research we've been doing to functionalize the surface of injection molds to promote filling of thin-wall cavities.

About the Author

Norbert Sparrow

Editor in chief of PlasticsToday since 2015, Norbert Sparrow has more than 30 years of editorial experience in business-to-business media. He studied journalism at the Centre Universitaire d'Etudes du Journalisme in Strasbourg, France, where he earned a master's degree.

www.linkedin.com/in/norbertsparrow

Sign up for PlasticsToday newsletter

You May Also Like