• Scientists develop a recyclable pollen-b

    From ScienceDaily@1:317/3 to All on Tue Apr 5 22:30:38 2022
    Scientists develop a recyclable pollen-based paper for repeated printing
    and `unprinting'

    Date:
    April 5, 2022
    Source:
    Nanyang Technological University
    Summary:
    Scientists have developed a pollen-based 'paper' that, after being
    printed on, can be 'erased' and reused multiple times without any
    damage to the paper.



    FULL STORY ========================================================================== Scientists at Nanyang Technological University, Singapore (NTU Singapore)
    have developed a pollen-based 'paper' that, after being printed on,
    can be 'erased' and reused multiple times without any damage to the paper.


    ==========================================================================
    In a research paper published online in Advanced Materialson 5 April,
    the NTU Singapore scientists demonstrated how high-resolution colour
    images could be printed on the non-allergenic pollen paper with a laser printer, and then 'unprinted' -- by completely removing the toner without damaging the paper - - with an alkaline solution. They demonstrated that
    this process could be repeated up to at least eight times.

    This innovative, printer-ready pollen paper could become an eco-friendly alternative to conventional paper, which is made via a multi-step process
    with a significant negative environmental impact, said the NTU team led
    by Professors Subra Suresh and Cho Nam-Joon.

    It could also help to reduce the carbon emissions and energy usage
    associated with conventional paper recycling, which involves repulping, de-toning (removal of printer toner) and reconstruction.

    The other members of this all-NTU research team are research fellow
    Dr Ze Zhao, graduate students Jingyu Deng and Hyunhyuk Tae, and former
    graduate student Mohammed Shahrudin Ibrahim.

    Prof Subra Suresh, NTU President and senior author of the paper, said:
    "Through this study, we showed that we could print high-resolution colour images on paper produced from a natural, plant-based material that was
    rendered non- allergenic through a process we recently developed. We
    further demonstrated the feasibility of doing so repeatedly without
    destroying the paper, making this material a viable eco-friendly
    alternative to conventional wood-based paper.

    This is a new approach to paper recycling -- not just by making paper
    in a more sustainable way, but also by extending the lifespan of the
    paper so that we get the maximum value out of each piece of paper we
    produce. The concepts established here, with further developments in
    scalable manufacturing, could be adapted and extended to produce other "directly printable" paper-based products such as storage and shipping
    cartons and containers." Prof Cho Nam-Joon, senior author of the paper,
    said: "Aside from being easily recyclable, our pollen-based paper is
    also highly versatile. Unlike wood-based conventional paper, pollen
    is generated in large amounts and is naturally renewable, making it
    potentially an attractive raw material in terms of scalability, economics,
    and environmental sustainability. In addition, by integrating conductive materials with the pollen paper, we could potentially use the material
    in soft electronics, green sensors, and generators to achieve advanced functions and properties."


    ==========================================================================
    This innovation adds to the series of discoveries and technological
    advances pioneered by NTU researchers from many disciplines,
    whose cutting-edge scholarly research translate NTU's commitment to sustainability into practices that benefit industry and society, in line
    with the vision outlined in the University's Sustainability Manifesto
    released in 2021 and the NTU 2025 strategic plan.

    A patent application has been filed based on this NTU innovation.

    A more sustainable way of papermaking Conventional paper is made of
    cellulose fibres found in wood, and the papermaking process involves energy-intensive steps that include logging, debarking, and chipping. With
    the pulp and paper industry accounting for 33 to 40 per cent of all
    industrial wood traded globally[1], this form of papermaking adds to
    the global problem of deforestation and rising carbon emissions.

    Pollen grains, in contrast, are generated regularly and in large amounts
    as genetic material carriers in plant reproduction. The process of making pollen- based paper is similar to traditional soapmaking, which is much
    simpler and less energy-intensive.



    ========================================================================== Using potassium hydroxide, the scientists first removed the cellular
    components encapsulated in tough sunflower pollen grains and turned them
    into soft microgel particles. This step also removes the component in
    pollen that causes allergies.

    The scientists then used deionised water to remove unwanted particles
    from the resulting pollen microgel, before casting it into a 22 cm x 22
    cm mould for air-drying. This forms a piece of paper that is about 0.03
    mm in thickness or about half the thickness of the human hair.

    Earlier research by the same NTU team has shown that pollen paper can
    bend and curl in response to moisture in the air. To 'stabilise' the
    paper and to render it insensitive to moisture, the scientists immersed
    it in acetic acid -- an active component in vinegar.

    Print, rinse, and repeat To demonstrate the printability of their
    sunflower pollen paper, the NTU scientists printed a painting from
    Vincent Van Gogh's Sunflowersseries using a laser printer. They found
    that the paper passed through the printer without any tear or damage.

    None of the toner powder particles came off when tape was stuck on
    the printed image and removed, suggesting that the toner layer was well-deposited on the pollen paper surface.

    While the colours of the image printed on pollen paper differed slightly
    from the same image printed on conventional paper (in part because of
    the differences in subsequent treatments), the image resolution and
    clarity on both types of paper were comparable.

    The scientists also found that subsequent immersion in water did not
    damage or soften the printed pollen paper -- an outcome essential for
    materials used for printing.

    The NTU team next showed that the pollen paper could be
    unprinted. "Unprinting" is a concept that has emerged in recent years
    as an eco-friendly alternative to conventional methods to remove toner
    from the used paper before it is recycled.

    This unprinting involves weakening of the bond between the toner powder
    and the paper for laser printing.

    The scientists did so by immersing the paper and rubbing it gently in
    a common lab reagent that is alkaline for two minutes. The pollen paper
    swelled when immersed in the alkaline solution, causing the toner layer
    to mechanically disintegrate and break away from the paper.

    Swollen from the unprinting process, the paper was then left to shrink
    in ethanol for five minutes, and air-dried. After treating it with acetic
    acid, the paper was ready for printing again.

    This process of treating pollen paper with acid, printing, then rinsing
    off the printed image, could be repeated another eight times without
    any loss of the paper's structural integrity or the quality of the
    printed images.

    This is in contrast to the unprinting techniques used for conventional
    paper which entail use of chemicals (e.g. chloroform or acetone) to
    weaken the bond between the toner and paper, or the use of high-intensity
    light to ablate the toner off the printed paper. Both these steps could
    damage the physical integrity of the paper, rendering it unsuitable for reprinting. In addition, the use of chemicals could pose environmental
    and health risks, said the scientists.

    Apart from sunflower pollen, the NTU scientists found that pollen grains
    from camellia and lotus could also be used to make a paper-like material, similar to the sunflower pollen paper. Their work thus shows that more
    than one type of pollen could be used to create pollen-based alternatives
    to conventional paper.

    This study builds on the team's body of research on pollen conducted
    at NTU over the past few years. Profs Cho and Suresh and their research
    team previously demonstrated that pollen paper could bend, curl, and even
    crawl like a caterpillar in response to changing levels of moisture in
    the air, making the material a potential candidate for applications in
    soft robotics.

    The same team also showed that they could get pollen paper to fold itself
    up into different 3D configurations by printing different patterns on
    the paper.

    [1] Pulp and paper, WWF Video: https://youtu.be/lqQ69Zl0z1o

    ========================================================================== Story Source: Materials provided by
    Nanyang_Technological_University. Note: Content may be edited for style
    and length.


    ========================================================================== Journal Reference:
    1. Ze Zhao, Jingyu Deng, Hyunhyuk Tae, Mohammed Shahrudin Ibrahim,
    Subra
    Suresh, Nam‐Joon Cho. Recyclable and Reusable Natural
    Plant‐Based Paper for Repeated Digital Printing and
    Unprinting.

    Advanced Materials, 2022; 2109367 DOI: 10.1002/adma.202109367 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220405092717.htm

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