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Building Microfluidic Devices From a Single Polymer: New Fabrication Process Discovered

Structural colour printing technology has the potential to allow for the development of better point-of-care diagnostic tools and miniature microsensors.

Microfluidic devices take advantage of the properties of liquids and gases at the microscale by confining tiny amounts of them in sub-millimetre spaces. So far, this technology has found uses in applications like DNA sequencing, inkjet printing, and point-of-care diagnostics. In addition, the technology may be used to miniaturise and automate chemical analyses that still require a whole lab, giving rise to the nickname of “lab-on-a-chip” for this subclass of devices.

Some of these applications require chips with higher resolution and narrow channel width, which have proved a challenge to manufacture using existing technologies. This is because the microfluidic channels have to be created from multiple components and assembled, with the assembly process being the most prone to introducing flaws into the final structures.

To reduce the need for assembly of such structures, researchers at Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) have innovated a new process that etches the complete structure directly into the starting material.

Unlike regular manufacturing processes, this process uses micro-LED light-sensitised polymers to create high-resolution, porous, and self-enclosed channels through a new photolithography technique. This process was created by Dr. Detao Qin of iCeMS’ Pureosity team, led by Professor Easan Sivaniah and is an extension of the team’s previous innovation from 2019, a printing process called “organised microfibrillation”, published in Nature.

Organised microfibrillation is a technique in which a standing-wave light pattern is shone on a photosensitive polymer, which leads to crosslinking of alternating layers of the polymer, causing stresses to build up in the unaffected layers. When it is treated with a weak solvent, the stresses in the unaffected layers cause microfibrils to form in the crosslinked layers, creating a new overall structure where porous layers are sandwiched between non-porous layers, giving rise to a structural colour effect – where the polymer looks coloured due to its microstructures. The porosity of the porous layers, which affects the flow rate of substances in the finished microfluidic device, may be modified by using a different wavelength of light, between 250 and 405 nm.

“We see great potential in this new process,” says Prof. Sivaniah. “It [is a] completely new platform for microfluidic technology, not just for personal diagnostics, but also for miniaturised sensors and detectors.”

The lab-on-a-chip technology, which makes use of microfluidic devices to analyse DNA and proteins, has already been adopted by the biomedical industry in point-of-care diagnostics. These tiny devices also have the potential to allow patients to monitor their vital health markers remotely so that any potential health issues may be detected early and treated promptly.

“It was exciting to finally use our technology for biomedical applications,” says Assistant Professor Masateru Ito, a co-author of the current paper. “We are taking the first steps, but it is encouraging that relevant biomolecules such as insulin and the SARS-CoV-2 shell protein were compatible with our channels. I think that diagnostic devices are a promising future for this technology.” [APBN]

Source: Qin et al. (2022). Structural colour enhanced microfluidics.Nature Communications,13(1), 1-9.