Scientists develop a recyclable pollen-based paper for repeated printing and ‘unprinting’ —

Scientists at Nanyang Technological College, Singapore (NTU Singapore) have developed a pollen-based ‘paper’ that, after being printed on, could be ‘erased’ and reused a number of occasions with none harm to the paper.

In a analysis paper revealed on-line in Superior Supplies on 5 April, the NTU Singapore scientists demonstrated how high-resolution color photos could possibly be printed on the non-allergenic pollen paper with a laser printer, after which ‘unprinted’ — by utterly eradicating the toner with out damaging the paper — with an alkaline answer. They demonstrated that this course of could possibly be repeated as much as a minimum of eight occasions.

This revolutionary, printer-ready pollen paper may turn out to be an eco-friendly various to standard paper, which is made through a multi-step course of with a big unfavorable environmental affect, stated the NTU workforce led by Professors Subra Suresh and Cho Nam-Joon.

It may additionally assist to scale back the carbon emissions and vitality utilization related to standard paper recycling, which includes repulping, de-toning (removing of printer toner) and reconstruction.

The opposite members of this all-NTU analysis workforce are analysis fellow Dr Ze Zhao, graduate college students Jingyu Deng and Hyunhyuk Tae, and former graduate scholar Mohammed Shahrudin Ibrahim.

Prof Subra Suresh, NTU President and senior creator of the paper, stated: “By means of this research, we confirmed that we may print high-resolution color photos on paper produced from a pure, plant-based materials that was rendered non-allergenic by a course of we just lately developed. We additional demonstrated the feasibility of doing so repeatedly with out destroying the paper, making this materials a viable eco-friendly various to standard wood-based paper. It is a new method to paper recycling — not simply by making paper in a extra sustainable means, but in addition by extending the lifespan of the paper in order that we get the utmost worth out of every piece of paper we produce. The ideas established right here, with additional developments in scalable manufacturing, could possibly be tailored and prolonged to supply different “instantly printable” paper-based merchandise akin to storage and transport cartons and containers.”

Prof Cho Nam-Joon, senior creator of the paper, stated: “Except for being simply recyclable, our pollen-based paper can also be extremely versatile. In contrast to wood-based standard paper, pollen is generated in massive quantities and is of course renewable, making it probably a gorgeous uncooked materials by way of scalability, economics, and environmental sustainability. As well as, by integrating conductive supplies with the pollen paper, we may probably use the fabric in smooth electronics, inexperienced sensors, and mills to attain superior capabilities and properties.”

This innovation provides to the sequence of discoveries and technological advances pioneered by NTU researchers from many disciplines, whose cutting-edge scholarly analysis translate NTU’s dedication to sustainability into practices that profit business and society, consistent with the imaginative and prescient outlined within the College’s Sustainability Manifesto launched in 2021 and the NTU 2025 strategic plan.

A patent software has been filed based mostly on this NTU innovation.

A extra sustainable means of papermaking

Typical paper is manufactured from cellulose fibres present in wooden, and the papermaking course of includes energy-intensive steps that embody logging, debarking, and chipping. With the pulp and paper business accounting for 33 to 40 per cent of all industrial wooden traded globally[1], this type of papermaking provides to the worldwide drawback of deforestation and rising carbon emissions.

Pollen grains, in distinction, are generated usually and in massive quantities as genetic materials carriers in plant copy. The method of creating pollen-based paper is much like conventional soapmaking, which is way less complicated and fewer energy-intensive.

Utilizing potassium hydroxide, the scientists first eliminated the mobile elements encapsulated in powerful sunflower pollen grains and turned them into smooth microgel particles. This step additionally removes the element in pollen that causes allergic reactions.

The scientists then used deionised water to take away undesirable particles from the ensuing pollen microgel, earlier than casting it right into a 22 cm x 22 cm mould for air-drying. This types a chunk of paper that’s about 0.03 mm in thickness or about half the thickness of the human hair.

Earlier analysis by the identical NTU workforce has proven that pollen paper can bend and curl in response to moisture within the air. To ‘stabilise’ the paper and to render it insensitive to moisture, the scientists immersed it in acetic acid — an energetic element in vinegar.

Print, rinse, and repeat

To reveal the printability of their sunflower pollen paper, the NTU scientists printed a portray from Vincent Van Gogh’s Sunflowers sequence utilizing a laser printer. They discovered that the paper handed by the printer with none tear or harm.

Not one of the toner powder particles got here off when tape was caught on the printed picture and eliminated, suggesting that the toner layer was well-deposited on the pollen paper floor.

Whereas the colors of the picture printed on pollen paper differed barely from the identical picture printed on standard paper (partially due to the variations in subsequent therapies), the picture decision and readability on each forms of paper had been comparable.

The scientists additionally discovered that subsequent immersion in water didn’t harm or soften the printed pollen paper — an final result important for supplies used for printing.

The NTU workforce subsequent confirmed that the pollen paper could possibly be unprinted. “Unprinting” is an idea that has emerged lately as an eco-friendly various to standard strategies to take away toner from the used paper earlier than it’s recycled. This unprinting includes 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 standard lab reagent that’s alkaline for 2 minutes. The pollen paper swelled when immersed within the alkaline answer, inflicting the toner layer to mechanically disintegrate and break free from the paper.

Swollen from the unprinting course of, the paper was then left to shrink in ethanol for 5 minutes, and air-dried. After treating it with acetic acid, the paper was prepared for printing once more.

This means of treating pollen paper with acid, printing, then rinsing off the printed picture, could possibly be repeated one other eight occasions with none lack of the paper’s structural integrity or the standard of the printed photos.

That is in distinction to the unprinting methods used for standard paper which entail use of chemical substances (e.g. chloroform or acetone) to weaken the bond between the toner and paper, or the usage of high-intensity gentle to ablate the toner off the printed paper. Each these steps may harm the bodily integrity of the paper, rendering it unsuitable for reprinting. As well as, the usage of chemical substances may pose environmental and well being dangers, stated the scientists.

Other than sunflower pollen, the NTU scientists discovered that pollen grains from camellia and lotus is also used to make a paper-like materials, much like the sunflower pollen paper. Their work thus exhibits that a couple of kind of pollen could possibly be used to create pollen-based alternate options to standard paper.

This research builds on the workforce’s physique of analysis on pollen performed at NTU over the previous few years. Profs Cho and Suresh and their analysis workforce beforehand demonstrated that pollen paper may bend, curl, and even crawl like a caterpillar in response to altering ranges of moisture within the air, making the fabric a possible candidate for functions in smooth robotics.

The identical workforce additionally confirmed that they might get pollen paper to fold itself up into totally different 3D configurations by printing totally different patterns on the paper.

[1] Pulp and paper, WWF