Professor of Microfluidics Discusses 3D Printing Benefits and Possible Future Improvements with Ultimaker

A lab-on-a-chip is pretty self-explanatory: it’s a miniature laboratory that is printed onto a microchip. But for the past 25 years, Professor David Barrow of Cardiff University in Wales has studied microfluidics, which is basically a small-scale plumbing system on a chip. Both of these tiny objects, which Professor Barrow has experience with, prove once again that bigger is not always better. Professor Barrow’s research laboratory, where he studies the application of microfluidics (also called microreactors) in different fields, uses Ultimaker 3D printers to create necessary microfluidic devices, in order to keep costs down and continue developing different design iterations at a faster rate of speed. His research, and at what points 3D printing technology intersects with it, was recently detailed in an Ultimaker blog post.

First, Professor Barrow explained a little more about microfluidics. The fluidic circuits can be used to make things like nano satellite propulsion systems, future chemical computers, and even small particles that are able to deliver pharmaceuticals inside the human body. Microfluidics can also analyze chemicals at a faster rate of speed and greater precision, with small volumes.

It is expensive and time-consuming to construct microfluidic chips: they have complex geometry, and some of the processes utilized to construct them are similar to the ones used to create electronic chips. Compared to the capabilities of standard clean room micromachining, 3D printing does have some limitations, in terms of materials, overall size, and resolution. But Cardiff University researchers weighed the risks against the benefits, and ultimately turned to 3D printing in order to develop “truly 3D features,” like a fluidic coil, for less time and money, and in their own laboratory.

Professor David Barrow [Image: Cardiff University]

“The simple purchase of a 3D printer means that as long as one is able to draw out an object in a suitable file format, using a wide range of available software tools, it is a relatively easy thing to print the object, and indeed make many revisions, relatively rapidly,” Professor Barrow told Ultimaker’s Caspar de Vries. “Ultimaker 3D printers are designed and built for fused deposition modeling with Ultimaker engineering thermoplastics within a commercial/business environment. The mixture of precision and speed makes the Ultimaker 3D printers the perfect machine for concept models, functional prototypes and the production of small series. Although we achieved a very high standard in the reproduction of 3D models with the usage of Cura, the user remains responsible to qualify and validate the application of the printed object for its intended use, especially critical for applications in strictly regulated areas like medical devices and aeronautics.”

Professor Barrow explained the current main areas of research at the laboratory:

• making protocells for studying membrane protein interactions
• nuclear fusion energy production
• encapsulation of the stem cells of the spinal cord

The lab uses 3D printing in its microfluidics research for a number of different applications, like making artificial, or minimal, cells for the development of pharmaceuticals. Professor Barrow explained that these cells are basically “liquid droplets within droplets” surrounded by lipid membranes, like the ones that make up human bodies. 3D printing is also used to make capsules from a biocompatible seaweed extract called alginate: the capsules contain neuronal stem cells, which are transplanted into people with spinal cord damage. Nuclear fusion targets, used for generating fusion energy, are also 3D printed in the lab. These small targets, or capsules, “contain frozen isotopes of hydrogen, and caused to implode using many lasers, just like at the US National Ignition Facility, or the French Laser Megajoule.”

Group Leader Oliver Castell said, “We can design small circuits to move around small volumes of fluid generally using technics borrowed from the microelectronics industry. Recently we started using 3D printing to make these microfluidics devices. It enables us to make microfluidic devices very rapidly, so we can iterate and improve upon those designs very quickly. It also enables us to make things very cheaply. We can share this technology with our collaborators and bring the microfluidics technology to other people and other researchers.”

Professor Barrow, when asked about 3D printing in other departments, said the School of Engineering already has several Ultimaker 3D printers, and that other schools, like the School of Pharmacy, were starting to come on board. Startup companies working at the university will soon have access to 3D printers in the university’s new print shop facility in the Innovation Centre, opening in November 2018. He said that with most simple 3D printers, as long as a person can draw an object in a suitable file format, it’s pretty easy to 3D print the object, and quickly make any necessary revisions.

“So making the printers as easy to use, and (critically) maintain, as paper printers, must be a key target goal,” Professor Barrow explained.

Speaking of critical, it’s necessary for Professor Barrow’s team to maintain control over the liquid contact angle of the 3D printed object’s material, and to print threaded ports within the material, so they can add fluid connections. That’s why they prefer Ultimaker’s 3D printers: as detailed in the team’s recent journal paper, Ultimaker machines can handle some of these specific features. Professor Barrow also explained that due to his department’s work in microfluidics, it’s necessary to be able to see into the capillary structures of the 3D printed objects, in order to observe the chip’s functionality. This is achieved by using light transmissive polymer fibers, or implanting a piece of light-transmissive material, like glass, inside opaque objects.

Any material they use needs to be leak-proof, as the researchers use these capillaries to transport fluids, and while Ultimaker’s FFF method of fabrication can cause small holes that lead to leaks, Professor Barrow says they just treat their 3D printed microfluidic devices with a chloroform vapor, to help seal them.

“By refining printing characteristics, I discovered that if you avoid the under-extrusion, you can make the devices transparent and water tight,” said Research Associate Alex Morgan.

Professor Barrow says they mostly stick with commercially available fibers, and modify them as needed post-fabrication, but that they’ve also worked with chemical functional groups called silanes, which can be added to the material surface and used to change the liquid contact angle. But they are looking for collaborators who have developed more customized fibers.

“What we are looking forward to is as the diversity of the materials you can print with expands and the resolution of printers improves we’ll be able to integrate not only fluidic circuits, but also implement optical and electronical components,” said Castell. “3D printing allows us to send the designs to another laboratory in Italy where they can print them and conduct experiments and report back the same day.”

Professor Barrow said a major microfluidic research development that could benefit from 3D printing technology is the necessity of printing multi-material structures, like integrated light pipes and electrical interconnects. He can also think of a few 3D printing improvements that would be “rather transformative,” like improving the printer compatible fiber supply chain to go beyond color changes, and instead print with materials that enable light piping, electrical conductivity, a diversity of liquid contact angles, and no plasticisers. He also thinks 3D printing could benefit from an increase in minimal feature and resolution size.

“We can attain embedded capillaries with diameter down to couple of hundred microns, but we really need to get this down to 50-100 microns,” Professor Barrow explained.

Ultimaker will soon publish another article on 3D printing in microfluidics research on its stories page, and it will be interesting to see if any similar points about the development of 3D printing are mentioned. Discuss in the Microfluidics forum at 3DPB.com.