Tag Archives: Stoyan K. Smoukov

A candy cane supercapacitor?

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Courtesy: Queen Mary University of London

It takes a lot more imagination than I have to describe the object on the right as resembling the  candy cane on the left, assuming that’s what was intended when it was used to illustrate the university’s press release. I like being pushed to see resemblances to things that are not immediately apparent to me. This may never look like a candy cane to me but I appreciate that someone finds it to be so. An August 16, 2017 news item on ScienceDaily announces the ‘candy cane’ supercapacitor,

Supercapacitors promise recharging of phones and other devices in seconds and minutes as opposed to hours for batteries. But current technologies are not usually flexible, have insufficient capacities, and for many their performance quickly degrades with charging cycles.

Researchers at Queen Mary University of London (QMUL) and the University of Cambridge have found a way to improve all three problems in one stroke.

Their prototyped polymer electrode, which resembles a candy cane usually hung on a Christmas tree, achieves energy storage close to the theoretical limit, but also demonstrates flexibility and resilience to charge/discharge cycling.

The technique could be applied to many types of materials for supercapacitors and enable fast charging of mobile phones, smart clothes and implantable devices.

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The Aug. 16, 2017 Queen Mary University of London (QMUL) press release (also on EurekAlert), which originated the news item, provides more detail about the technology,

Pseudocapacitance is a property of polymer and composite supercapacitors that allows ions to enter inside the material and thus pack much more charge than carbon ones that mostly store the charge as concentrated ions (in the so-called double layer) near the surface.

The problem with polymer supercapacitors, however, is that the ions necessary for these chemical reactions can only access the top few nanometers below the material surface, leaving the rest of the electrode as dead weight. Growing polymers as nano-structures is one way to increase the amount of accessible material near the surface, but this can be expensive, hard to scale up, and often results in poor mechanical stability.

The researchers, however, have developed a way to interweave nanostructures within a bulk material, thereby achieving the benefits of conventional nanostructuring without using complex synthesis methods or sacrificing material toughness.

Project leader, Stoyan Smoukov, explained: “Our supercapacitors can store a lot of charge very quickly, because the thin active material (the conductive polymer) is always in contact with a second polymer which contains ions, just like the red thin regions of a candy cane are always in close proximity to the white parts. But this is on a much smaller scale.

“This interpenetrating structure enables the material to bend more easily, as well as swell and shrink without cracking, leading to greater longevity. This one method is like killing not just two, but three birds with one stone.”

The outcomes

The Smoukov group had previously pioneered a combinatorial route to multifunctionality using interpenetrating polymer networks (IPN) in which each component would have its own function, rather than using trial-and-error chemistry to fit all functions in one molecule.

This time they applied the method to energy storage, specifically supercapacitors, because of the known problem of poor material utilization deep beneath the electrode surface.

This interpenetration technique drastically increases the material’s surface area, or more accurately the interfacial area between the different polymer components.

Interpenetration also happens to solve two other major problems in supercapacitors. It brings flexibility and toughness because the interfaces stop growth of any cracks that may form in the material. It also allows the thin regions to swell and shrink repeatedly without developing large stresses, so they are electrochemically resistant and maintain their performance over many charging cycles.

The researchers are currently rationally designing and evaluating a range of materials that can be adapted into the interpenetrating polymer system for even better supercapacitors.

In an upcoming review, accepted for publication in the journal Sustainable Energy and Fuels, they overview the different techniques people have used to improve the multiple parameters required for novel supercapacitors.

Such devices could be made in soft and flexible freestanding films, which could power electronics embedded in smart clothing, wearable and implantable devices, and soft robotics. The developers hope to make their contribution to provide ubiquitous power for the emerging Internet of Things (IoT) devices, which is still a significant challenge ahead.

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

Semi-Interpenetrating Polymer Networks for Enhanced Supercapacitor Electrodes by Kara D. Fong, Tiesheng Wang, Hyun-Kyung Kim, R. Vasant Kumar, and Stoyan K. Smoukov. ACS Energy Lett., 2017, 2, pp 2014–2020 DOI: 10.1021/acsenergylett.7b00466 Publication Date (Web): August 14, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

‘Hotel for cells’ or minuscule artificial scaffolding units for plant tissue engineering

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This is the first time I’ve seen an item about tissue engineering which concerns plant life.  An August 27, 2015 news item on Azonano describes the latest development with plant cells,

Miniscule artificial scaffolding units made from nano-fibre polymers and built to house plant cells have enabled scientists to see for the first time how individual plant cells behave and interact with each other in a three-dimensional environment.

These “hotels for cells” mimic the ‘extracellular matrix’ which cells secrete before they grow and divide to create plant tissue. [Note: Human and other cells also have extracellular matrices] This environment allows scientists to observe and image individual plant cells developing in a more natural, multi-dimensional environment than previous ‘flat’ cell cultures.

An August 26, 2015 University of Cambridge press release, which originated the news item, describes the research and mentions the pioneering technologies which made it possible,

The research team were surprised to see individual plant cells clinging to and winding around their fibrous supports; reaching past neighbouring cells to wrap themselves to the artificial scaffolding in a manner reminiscent of vines growing.

Pioneering new in vitro techniques combining recent developments in 3-D scaffold development and imaging, scientists say they observed plants cells taking on growth and structure of far greater complexity than has ever been seen of plant cells before, either in living tissue or cell culture.

“Previously, plant cells in culture had only been seen in round or oblong forms. Now, we have seen 3D cultured cells twisting and weaving around their new supports in truly remarkable ways, creating shapes we never thought possible and never seen before in any plant,” said plant scientist and co-author Raymond Wightman.

“We can use this tool to explore how a whole plant is formed and at the same time to create new materials.”

This ability for single plant cells to attach themselves by growing and spiralling around the scaffolding suggests that cells of land plants have retained the ability of their evolutionary ancestors – aquatic single-celled organisms, such as Charophyta algae – to stick themselves to inert structures.

While similar ‘nano-scaffold’ technology has long been used for mammalian cells, resulting in the advancement of tissue engineering research, this is the first time such technology has been used for plant cells – allowing scientists to glimpse in 3-D the individual cell interactions that lead to the forming of plant tissue.

The scientists say the research “defines a new suite of techniques” for exploring cell-environment interactions, allowing greater understating of fundamental plant biology that could lead to new types of biomaterials and help provide solutions to sustainable biomass growth.

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“While we can peer deep inside single cells and understand their functions, when researchers study a ‘whole’ plant, as in fully formed tissue, it is too difficult to disentangle the many complex interactions between the cells, their neighbours, and their behaviour,” said Wightman.

“Until now, nobody had tried to put plant cells in an artificial fibre scaffold that replicates their natural environment and tried to observe their interactions with one or two other cells, or fibre itself,” he said.

Co-author and material scientist Dr Stoyan Smoukov suggests that a possible reason why artificial scaffolding on plant cells had never been done before was the expense of 3D nano-fibre matrices (the high costs have previously been justified in mammalian cell research due to its human medical potential).

However, Smoukov has co-discovered and recently helped commercialise a new method for producing polymer fibres for 3-D scaffolds inexpensively and in bulk. ‘Shear-spinning’ produces masses of fibre, in a technique similar to creating candy-floss in nano-scale. The researchers were able to adapt such scaffolds for use with plant cells.

This approach was combined with electron microscopy imaging technology. In fact, using time-lapse photography, the researchers have even managed to capture 4-D footage of these previously unseen cellular structures. “Such high-resolution moving images allowed us to follow internal processes in the cells as they develop into tissues,” said Smoukov, who is already working on using the methods in this plant study to research mammalian cancer cells.

Here’s an image illustrating the research,

Plant cells twisting and weaving in 3-D cultures Credit: Smoukov/Wightman

Plant cells twisting and weaving in 3-D cultures
Credit: Smoukov/Wightman

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

A 3-dimensional fibre scaffold as an investigative tool for studying the morphogenesis of isolated plant pells [cells?] by CJ Luo, Raymond Wightman, Elliot Meyerowitz, and Stoyan K. Smoukov. BMC Plant Biology 2015, 15:211 doi:10.1186/s12870-015-0581-7

This paper is open access.