Tag Archives: agar (agar agar)

Stifle the noise with seaweed

The claim that most spaces are now designed with sound-absorption in mind seems a little overblown to me but judge for yourself, from a July 14, 2022 news item on phys.org,

From airplanes to apartments, most spaces are now designed with sound-absorbing materials that help dampen the droning, echoing and murmuring sounds of everyday life. But most of the acoustic materials that can cancel out human voices, traffic and music are made from plastic foams that aren’t easily recycled or degraded. Now, researchers reporting in ACS Sustainable Chemistry & Engineering have created a biodegradable seaweed-derived film that effectively absorbs sounds in this range.

A July 14, 2022 American Chemical Society (ACS) news release (also on EurekAlert), which originated the news item, describes the work in more detail,

Controlling and optimizing the way sound moves throughout a room is key to creating functional spaces. Foam acoustic panels are a common solution, and they come in a variety of materials and thicknesses tailored to specific sound requirements. Most of these foams, however, are made from polyurethane and other polymers that are derived from crude oil or shale gas. To avoid petrochemicals, researchers have explored more renewably sourced and biodegradable sound-absorbing alternatives. But many current options are made from plant fibers that don’t effectively dampen noises in the most useful range of sound frequencies, or they are too thick or unwieldy to fabricate. So, Chindam Chandraprakash and colleagues wanted to develop a plant-derived, biodegradable material that would be simple to manufacture and that could absorb a range of sounds.

The team created thin films of agar, a jelly-like material that comes from seaweed, along with other plant-derived additives and varied both the thickness and porosity of the films. After running the materials through a battery of tests, the researchers measured how well the films dampened sound across a range of frequencies — from a bass hum to a shrill whine. To do this, the team created a sound tube in which a speaker is placed at one end, and the test film is fitted over the other end. Microphones in the middle of the tube measured the amount of sound emitted by the speaker and the amount of sound reflected off the film. These experiments showed that porous films made with the highest concentrations of agar had the greatest sound-absorbing qualities and performed similarly to traditional acoustic foams. The researchers plan to explore ways to modify the agar films to give them other desirable properties, such as flame resistance, and will explore other biologically derived film materials.

Here’s a link to and a citation for the paper,

Agar-Based Composite Films as Effective Biodegradable Sound Absorbers by Surendra Kumar, Kousar Jahan, Abhishek Verma, Manan Agarwal, and C. Chandraprakash. ACS Sustainable Chem. Eng. 2022, 10, 26, 8242–8253 DOI: https://doi.org/10.1021/acssuschemeng.2c00168 Publication Date: June 23, 2022 Copyright © 2022 American Chemical Society

This paper is behind a paywall.

Optical fibers made from marine algae

Apparently after you’ve finished imaging with your marine algae-based optical fibers, you can eat them. A July 24, 2020 news item on Nanowerk announces the new research,

An optical fiber made of agar has been produced at the University of Campinas (UNICAMP) in the state of São Paulo, Brazil. This device is edible, biocompatible and biodegradable. It can be used in vivo for body structure imaging, localized light delivery in phototherapy or optogenetics (e.g., stimulating neurons with light to study neural circuits in a living brain), and localized drug delivery.

Another possible application is the detection of microorganisms in specific organs, in which case the probe would be completely absorbed by the body after performing its function.

Caption: Edible, biocompatible and biodegradable, these fibers have potential for various medical applications. Credit: Eric Fujiwara

A July 24, 2020 Fundação de Amparo à Pesquisa dFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) do Estado de São Paulo press release on EurekAlert, which originated the news item, provides a few more details about the researches and the work,

The research project, which was supported by São Paulo Research Foundation – FAPESP, was led by Eric Fujiwara, a professor in UNICAMP’s School of Mechanical Engineering, and Cristiano Cordeiro, a professor in UNICAMP’s Gleb Wataghin Institute of Physics, in collaboration with Hiromasa Oku, a professor at Gunma University in Japan.

An article on the study is published) in Scientific Reports, an online journal owned by Springer Nature.

Agar, also called agar-agar, is a natural gelatin obtained from marine algae. Its composition consists of a mixture of two polysaccharides, agarose and agaropectin. “Our optical fiber is an agar cylinder with an external diameter of 2.5 millimeters [mm] and a regular inner arrangement of six 0.5 mm cylindrical airholes around a solid core. Light is confined owing to the difference between the refraction indices of the agar core and the airholes,” Fujiwara told.

“To produce the fiber, we poured food-grade agar into a mold with six internal rods placed lengthwise around the main axis,” he continued. “The gel distributes itself to fill the available space. After cooling, the rods are removed to form airholes, and the solidified waveguide is released from the mold. The refraction index and geometry of the fiber can be adapted by varying the composition of the agar solution and mold design, respectively.”

The researchers tested the fiber in different media, from air and water to ethanol and acetone, concluding that it is context-sensitive. “The fact that the gel undergoes structural changes in response to variations in temperature, humidity and pH makes the fiber suitable for optical sensing,” Fujiwara said.

Another promising application is its simultaneous use as an optical sensor and a growth medium for microorganisms. “In this case, the waveguide can be designed as a disposable sample unit containing the necessary nutrients. The immobilized cells in the device would be optically sensed, and the signal would be analyzed using a camera or spectrometer,” he said.


About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at http://www.fapesp.br/en and visit FAPESP news agency at http://www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

As per my usual practice, here’s a link to and a citation for the paper,

Agarose-based structured optical fibre by Eric Fujiwara, Thiago D. Cabral, Miko Sato, Hiromasa Oku & Cristiano M. B. Cordeiro. Scientific Reports volume 10, Article number: 7035 (2020) DOI: https://doi.org/10.1038/s41598-020-64103-3 Published: 27 April 2020

This paper is open access.

Should you have a problem accessing the English language version of the FAPESP website, the Portuguese language version of the site seems more accessible (assuming you have the language skills).