SUTD's novel approach allows 3D printing of finer, more complex microfluidic networks

January 30, 2020

First introduced in the 1980s, stereolithography (SL) is an additive manufacturing process that prints 3D objects by the selective curing of liquid polymer resin using an ultra-violet (UV) light source in a layer-by-layer fashion. The polymer employed undergoes a photochemical reaction which turns it from liquid to solid when exposed to UV illumination. Today, SL is touted as one of the most accurate forms of 3D printing that is accessible to consumers, with desktop models (e.g., liquid crystal display variants) costing as little as USD 300.

SL is an attractive option for researchers in the field of microfluidics. Not only does it have the ability to fabricate microfluidic devices in a single step from a computer-generated model, but it also allows the fabrication of truly 3D structures that would otherwise have been challenging, if not impossible, with the existing fabrication approaches.

However, when employing SL printers in printing microfluidic channels, two representative problems occur. Firstly, inadvertent polymerization of uncured resin in channel void. During the print, the liquid resin is trapped within the channel void. Illumination from subsequent layers may inadvertently cure the trapped liquid resin, which will result in a channel clog.

Secondly, in the event where inadvertent polymerization of resin does not occur, the evacuation of the trapped resin within the channel void can still be a challenge. This is because existing liquid resin is viscous (i.e., consistency like honey), making the evacuation of narrow channels or networks with multiple branches challenging. These two challenges limit the attainability of channel dimensions and complexity in fluidic networks printed by SL.

To tackle these limitations, researchers from the Singapore Unversity of Technology and Design (SUTD) in collaboration with Assistant Professor Toh Yi-Chin's research group from the National University of Singapore, developed a design approach that can improve the attainable channel dimensions and complexity of networks with existing SL (refer to image).

"The conventional way of printing microfluidic devices with SL printers is to print the entire device as a monolithic entity. However, issues like inadvertent polymerization of channel void and difficulty in evacuating channel void arises from printing as a monolithic entity," explained principal investigator Assistant Professor Michinao Hashimoto from Engineering Product Development, SUTD.

Instead, the researchers took a modularization approach - where they spatially deconstructed a microfluidic channel into simpler subunits, printed them separately, and subsequently assembled them to form microfluidic networks. By applying this approach, they were able to print microfluidic networks with greater intricacy (such as hierarchical branching) and smaller channel dimensions.

"By design, each subunit is spatially deconstructed to have simple geometries that would not result in inadvertent polymerization. The simple geometries also facilitated the evacuation of uncured resin," said lead author Terry Ching, a graduate student from SUTD.

The team was able to fabricate a range of fluidic networks that were challenging to print using conventional methods. Their demonstration includes hierarchical branching networks, rectilinear lattice networks, helical networks, etc. They were also able to demonstrate the efficacy of their approach by showing a substantial improvement channel dimensions (i.e., channel w = 75 μm and h = 90 μm) when compared to using the conventional 'monolithic' printing approach.

One obvious use case is the application of this approach to fabricate fluidic networks using hydrogel to mimic native vasculature. To date, the variety of SL printable hydrogels is limited, and they often lack mechanical properties necessary for an accurate print or biocompatibility required for the incorporation of living cells. By simplifying the geometries of each subunit, the team used hydrogel to fabricate intricate fluidic networks, mimicking native vasculature.

"Simplifying the geometries of the subunits also reduces the use of additives that may be harmful to biological cells," added Ching.

All in all, this is a general design approach that can circumvent some of the biggest challenges in SL printed microfluidics - by applying this approach, existing SL printers can now fabricate microfluidics with finer channel dimensions, and more branching intricacies. This research paper has been published in Advanced Engineering Materials.
-end-


Singapore University of Technology and Design

Related Networks Articles from Brightsurf:

New research may help identify sex trafficking networks
Characterizing traits of online activity may help to rescue victims of sex trafficking.

Social networks can support academic success
Social networks have been found to influence academic performance: students tend to perform better with high-performers among their friends, as some people are capable of inspiring others to try harder, according to Sofia Dokuka, Dilara Valeyeva and Maria Yudkevich of the HSE University.

A clique away from more efficient networks
An old branch of mathematics finds a fertile new field of application.

Get excited by neural networks
Scientists at The University of Tokyo introduced a new method for inferring the energy of the excited states of electrons in materials using machine learning.

Shaping the social networks of neurons
Identification of a protein complex that attracts or repels nerve cells during development.

Mapping the relay networks of our brain
A team of scientists led by Karl Farrow at NeuroElectronics Research Flanders (NERF, empowered by imec, KU Leuven and VIB) is unraveling how our brain processes visual information.

Hidden dynamics detected in neuronal networks
Neuronal networks in the brain can process information particularly well when they are close to a critical.

Exploring deeper understanding and better description of networks
In network science, switching the focus from node degrees to network cycles could reveal many interesting properties from the perspective of totally homogenous networks.

Social networks and suicide prevention
Depression and mental health problems are increasing - and suicide and drug overdose rates are rising dramatically in the USA.

Do all networks obey the scale-free law? Maybe not
A new study debunks a popular, two-decade-old theory about the shape of networks.

Read More: Networks News and Networks Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.