Diagnosing genetic mutations and anomalies is a tricky science. In Dino Di Carlo’s lab at the University of California, Los Angeles, that science involves the careful preparation of microfluidic chips. These chips contain miniscule channels through which fluid samples will travel, and their preparation has to take place in a special clean room to prevent even a speck of dust from blocking one of the channels. Manufacturing them is a difficult and tedious job, but Di Carlo and his team are working to find an easier and less expensive way.
Microfluidic circuits allow scientists to maximize the results they can get from limited or expensive samples. Working with such small volumes enables multiple analyses to be conducted at the same time, and the technology also lends itself to automation, as only machines can manipulate such tiny volumes. That reduces human error, meaning that even technicians with minimal training would be able to perform testing.
It’s not that easy, though. So far, developers have focused on miniaturizing processes used to analyze DNA or RNA in blood or other bodily fluids, but using a microchip often requires those fluids to have already undergone some processing to remove components that could interfere with the reactions. The challenge, according to Jean-Louis Viovy, research director at France’s basic-research agency, the CNRS, and scientific founder of microfluidics company Fluigent, is “trying to expand the toolbox of microfluidics to be able to go from the real sample to the results, all in microfluidics.”
Di Carlo’s lab came up with a method for isolating circulating tumor cells, a valuable tool for cancer diagnosis. The lab uses photolithography to make microchips out of PDMS, a transparent rubber. Working in a clean room, engineers spread a liquid solution onto a circular silicon plate, and then cover the polymer with a printed black photomask that contains clear portions in the pattern of the required channels. They then expose it to ultraviolet light to cure the exposed sections, creating an inverse cast of the chip.
Liquid PDMS is then poured over the cast and baked, and a glass slide is fused to the bottom to create a prototype. Plastic copies are then ordered. That’s one way to create a 2D chip, but what about when a 3D one is required? In the past, scientists have had to stack several layers of a polymer into the photolithography molds, but 3D printing is making the process easier.
Vittorio Saggiomo, a chemist at Wageningen University, is also a 3D printing enthusiast. He 3D prints small tools for the lab, as well as fun stuff such as figurines and bird houses. Once, he accidentally left a print too long in acetone, and it dissolved. Out of that mishap came an epiphany: he could adapt that process to create microchannels. Saggiomo and his colleague, Aldrik Velders, 3D printed the shape of the channel they wanted and then suspended the printed piece in PDMS. They then soaked it in acetone overnight, which dissolved the plastic and left behind a ready-to-use microchip.The method proved useful for creating microchips with complex patterns that would be difficult to create otherwise. One chip, for example, had a straight channel surrounded by a coiled one. According to Saggiomo, users could run hot or cold water through the coil in order to change the temperature of a sample.
Although standardized designs are being developed for microchips, said Di Carlo, there’s a lot of room for variety, and different designs can affect the repeatability of an experiment. His lab’s goal is to make microchips both more effective and more affordable, and while 3D printing is only one of the ways that researchers are experimenting with microchip design, it’s an effective way. Specialized 3D printers have even been designed for the production of microfluidic chips; the 3D printing of such devices is an emerging field and one that could potentially save lives by making diagnostic technology faster and more effecitve. Discuss in the 3D Printed Microfluidic Chips forum at 3DPB.com.[Source: Nature]
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