Tag Archives: Amir Sheikhi

Drying and redispersing cellulose nanocrystals (CNC)

A January 11, 2023 news item on ScienceDaily announces some new research on cellulose nanocrystals (CNC),

Cellulose nanocrystals—bio-based nanomaterials derived from natural resources such as plant cellulose—are valuable for their use in water treatment, packaging, tissue engineering, electronics, antibacterial coatings and much more. Though the materials provide a sustainable alternative to non-bio-based materials, transporting them in liquid taxes industrial infrastructures and leads to environmental impacts.

A team of Penn State [Pennsylvania State University] chemical engineering researchers studied the mechanisms of drying the nanocrystals and proposed nanotechnology to render the nanocrystals highly redispersible in aqueous mediums, while retaining their full functionality, to make them easier to store and transport. They published their results in the journal Biomacromolecules.

This image illustrates what the drying process does,

This graphic representation of hairy cellulose nanocrystals, shown attached at their hairy ends when dried (right), will be featured as the Biomacromolecules journal cover in the Jan. 17 issue. Credit: Sheikhi Research Group. All Rights Reserved.

A Pennsylvania State University (Penn State) news release (also on EurekAlert) by Mariah R. Lucas, which originated the news item, provides more detail, Note: A link has been removed,

“We looked at how we could take hairy nanocrystals, dry them in ovens, and redisperse them in solutions containing different ions,” said co-first author Breanna Huntington, current chemical engineering doctoral student at the University of Delaware and former member of the Sheikhi Research Group while an undergraduate student at Penn State. “We then compared their functionality to conventional, non-hairy cellulose nanocrystals.”  

The nanocrystals have negatively charged cellulose chains at their ends, known as hairs. When rehydrated, the hairs repel each other and separate, dispersing again through a liquid, as a result of electrosteric repulsion — a term meaning charge-driven, or electrostatic, and free-volume dependent, or steric.  

“The hairy ends of the nanocrystals are nanoengineered to be negatively charged and repel each other when placed in an aqueous medium,” said corresponding author Amir Sheikhi, Penn State assistant professor of chemical engineering and of biomedical engineering. “To have maximum function, the nanocrystals must be separate, individual particles, not chained together as they are when they are dry.” 

After the hairy particles were redispersed, researchers tested them and measured their size and surface properties and found their characteristics and performance were the same as those that had never been dried. They also found the particles could perform well and maintain their stability in a variety of liquid mixtures of different salinities and pH levels.

“The hairy nanocrystals can become redispersed even at high salt concentrations, which is convenient, as they remain functional in harsh media and may be used in a broad range of applications,” said co-first author Mica Pitcher, Penn State doctoral student in chemistry, supervised by Sheikhi. “This work may pave the way for sustainable and large-scale processing of nanocelluloses without using additive or energy-intensive methods.” 

The Penn State College of Engineering Summer Research Experiences for Undergraduates program and the NASA Pennsylvania Space Grant Consortium graduate fellowship program supported this work.  

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

Nanoengineering the Redispersibility of Cellulose Nanocrystals by Breanna Huntington, Mica L. Pitcher, and Amir Sheikhi. Biomacromolecules 2023, 24, 1, 43–56 DOI: https://doi.org/10.1021/acs.biomac.2c00518 Publication Date:December 5, 2022 Copyright © 2022 American Chemical Society

This paper is behind a paywall.

Flexible graphene-rubber sensor for wearables

Courtesy: University of Waterloo

This waffled, greyish thing may not look like much but scientists are hopeful that it can be useful as a health sensor in athletic shoes and elsewhere. A March 6, 2020 news item on Nanowerk describes the work in more detail (Note: Links have been removed),

Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance (ACS Nano, “3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring”).

The new technology, developed by engineers at the University of Waterloo [Ontario, Canada], combines silicone rubber with ultra-thin layers of graphene in a material ideal for making wristbands or insoles in running shoes.

A March 6, 2020 University of Waterloo news release, which originated the news item, delves further,

When that rubber material bends or moves, electrical signals are created by the highly conductive, nanoscale graphene embedded within its engineered honeycomb structure.

“Silicone gives us the flexibility and durability required for biomonitoring applications, and the added, embedded graphene makes it an effective sensor,” said Ehsan Toyserkani, research director at the Multi-Scale Additive Manufacturing (MSAM) Lab at Waterloo. “It’s all together in a single part.”

Fabricating a silicone rubber structure with such complex internal features is only possible using state-of-the-art 3D printing – also known as additive manufacturing – equipment and processes.

The rubber-graphene material is extremely flexible and durable in addition to highly conductive.

“It can be used in the harshest environments, in extreme temperatures and humidity,” said Elham Davoodi, an engineering PhD student at Waterloo who led the project. “It could even withstand being washed with your laundry.”

The material and the 3D printing process enable custom-made devices to precisely fit the body shapes of users, while also improving comfort compared to existing wearable devices and reducing manufacturing costs due to simplicity.

Toyserkani, a professor of mechanical and mechatronics engineering, said the rubber-graphene sensor can be paired with electronic components to make wearable devices that record heart and breathing rates, register the forces exerted when athletes run, allow doctors to remotely monitor patients and numerous other potential applications.

Researchers from the University of California, Los Angeles and the University of British Columbia collaborated on the project.

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

3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring by Elham Davoodi, Hossein Montazerian, Reihaneh Haghniaz, Armin Rashidi, Samad Ahadian, Amir Sheikhi, Jun Chen, Ali Khademhosseini, Abbas S. Milani, Mina Hoorfar, Ehsan Toyserkani. ACS Nano 2020, 14, 2, 1520-1532 DOI: https://doi.org/10.1021/acsnano.9b06283 Publication Date: January 6, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.