• New 3D printing technique: A game change

    From ScienceDaily@1:317/3 to All on Tue Apr 12 22:30:44 2022
    New 3D printing technique: A game changer for medical testing devices


    Date:
    April 12, 2022
    Source:
    University of Southern California
    Summary:
    Researchers have developed a 3D printing technique to fabricate
    microfluidic devices for biomedical applications at a microscale
    not previously possible.



    FULL STORY ========================================================================== Microfluidic devices are compact testing tools made up of tiny channels
    carved on a chip, which allow biomedical researchers to test the
    properties of liquids, particles and cells at a microscale. They are
    crucial to drug development, diagnostic testing and medical research in
    areas such as cancer, diabetes and now COVID-19. However, the production
    of these devices is very labor intensive, with minute channels and
    wells that often need to be manually etched or molded into a transparent
    resin chip for testing. While 3D printing has offered many advantages
    for biomedical device manufacturing, its techniques were previously not sensitive enough to build layers with the minute detail required for microfluidic devices. Until now.


    ========================================================================== Researchers at the USC Viterbi School of Engineering have now developed
    a highly specialized 3D printing technique that allows microfluidic
    channels to be fabricated on chips at a precise microscale not previously achieved. The research, led by Daniel J. Epstein Department of Industrial
    and Systems Engineering Ph.D. graduate Yang Xu and Professor of Aerospace
    and Mechanical Engineering and Industrial and Systems Engineering
    Yong Chen, in collaboration with Professor of Chemical Engineering and Materials Science Noah Malmstadt and Professor Huachao Mao at Purdue University, was published in Nature Communications.

    The research team used a type of 3D printing technology known as vat photopolymerization, which harnesses light to control the conversion of
    liquid resin material into its solid end state.

    "After light projection, we can basically decide where to build the parts
    (of the chip), and because we use light, the resolution can be rather high within a layer. However, the resolution is much worse between layers,
    which is a critical challenge in the building of microscale channels,"
    Chen said.

    "This is the first time we've been able to print something where the
    channel height is at the 10 micron level; and we can control it really accurately, to an error of plus or minus one micron. This is something
    that has never been done before, so this is a breakthrough in the 3D
    printing of small channels," he said.

    Vat photopolymerization makes use of a vat filled with liquid
    photopolymer resin, out of which a printed item is constructed layer
    by layer. Ultraviolet light is then flashed onto the object, curing
    and hardening the resin at each layer level. As this happens, a build
    platform moves the printed item up or down so additional layers can be
    built onto it.



    ==========================================================================
    But when it comes to microfluidic devices, vat photopolymerization has
    some disadvantages in the creation of the tiny wells and channels that
    are required on the chip. The UV light source often penetrates deeply
    in the residual liquid resin, curing and solidifying material within
    the walls of the device's channels, which would clog the finished device.

    "When you project the light, ideally, you only want to cure one layer of
    the channel wall and leave the liquid resin inside the channel untouched;
    but it's hard to control the curing depth, as we are trying to target
    something that is only a 10 micron gap," Chen said.

    He said that current commercial processes only allowed for the creation of
    a channel height at the 100 microns level with poor accuracy control, due
    to the fact that the light penetrates a cured layer too deeply, unless you
    are using an opaque resin that doesn't allow as much light penetration.

    "But with a microfluidic channel, typically you want to observe something
    under microscope, and if it's opaque, you cannot see the material inside,
    so we need to use a transparent resin," Chen said.

    In order to accurately create channels in clear resin at a microscale
    level suitable for microfluidic devices, the team developed a unique
    auxiliary platform that moves between the light source and the printed
    device, blocking the light from solidifying the liquid within the walls
    of a channel, so that the channel roof can then be added separately to
    the top of the device. The residual resin that remains in the channel
    would still be in a liquid state and can then be flushed out after the
    printing process to form the channel space.



    ========================================================================== Microfluidic devices have increasingly important applications in medical research, drug development and diagnostics.

    "There are so many applications for microfluidic channels. You can flow
    a blood sample through the channel, mixing it with other chemicals so
    you can, for example, detect whether you have COVID or high blood sugar levels," Chen said.

    He said the new 3D printing platform, with its microscale channels,
    allowed for other applications, such as particle sorting. A particle
    sorter is a type of microfluidic chip that makes use of different sized chambers that can separate different sized particles. This could offer significant benefits to cancer detection and research.

    "Tumor cells are slightly bigger than normal cells, which are around 20 microns. Tumor cells could be over 100 microns," Chen said. "Right now,
    we use biopsies to check for cancer cells; cutting organ or tissue from
    a patient to reveal a mix of healthy cells and tumor cells. Instead,
    we could use simple microfluidic devices to flow (the sample) through
    channels with accurately printed heights to separate cells into
    different sizes so we don't allow those healthy cells to interfere with
    our detection." Chen said the research team was now in the process
    of filing a patent application for the new 3D printing method, and is
    seeking collaboration to commercialize the fabrication technique for
    medical testing devices.


    ========================================================================== Story Source: Materials provided by
    University_of_Southern_California. Original written by Greta
    Harrison. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Yang Xu, Fangjie Qi, Huachao Mao, Songwei Li, Yizhen Zhu,
    Jingwen Gong,
    Lu Wang, Noah Malmstadt, Yong Chen. In-situ transfer vat
    photopolymerization for transparent microfluidic device fabrication.

    Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28579-z ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220412095405.htm

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