̽��ֱ�� of Cambridge - Stoyan Smoukov

New understanding of how shape and form develop in nature

sc604 — Wed, 09 Dec 2015 18:01:07 +0000

Researchers have developed a new method for generating complex shapes, and have found that the development of form in nature can be driven by the physical properties of materials themselves, in contrast with earlier findings. ̽��ֱ��results, reported in the journal Nature, could enable the construction of complex structures from simple components, with potential applications in pharmaceuticals, paints, cosmetics and household products such as shampoo.

Using a simple set-up – essentially droplets of oil in a soapy water solution which were slowly frozen – the researchers found that recently-discovered ‘plastic crystal’ phases formed on the inside surfaces of the droplets causes them to shape-shift into a wide variety of forms, from octahedrons and hexagons to triangles and fibres.

Previous efforts to create such complex shapes and structures have used top-down processing methods, which allow a high degree of control, but are not efficient in terms of the amount of material used or the expensive equipment necessary to make the shapes. ̽��ֱ��new method, developed by researchers from the ̽��ֱ�� of Cambridge and Sofia ̽��ֱ�� in Bulgaria, uses a highly efficient, extremely simple bottom-up approach to create complex shapes.

“There are many ways that non-biological things take shape,” said Dr Stoyan Smoukov from Cambridge’s Department of Materials Science & Metallurgy, who led the research. “But the question is what drives the process and how to control it – and what are the links between the process in the biological and the non-biological world?”

Smoukov’s research proposes a possible answer to the question of what drives this process, called morphogenesis. In animals, morphogenesis controls the distribution of cells during embryonic development, and can also be seen in mature animals, such as in a growing tumour.

In the 1950s, the codebreaker and mathematician Alan Turing proposed that morphogenesis is driven by reaction-diffusion, in which local chemical reactions cause a substance to spread through a space. More recent research, from Smoukov’s group and others, has proposed that it is physical properties of materials that control the process. This possibility had been anticipated by Turing, but it was impossible to determine using the computers of the time.

What this most recent research has found is that by slowly freezing oil droplets in a soapy solution, the droplets will shape-shift through a variety of different forms, and can shift back to their original shape if the solution is re-warmed. Further observation found that this process is driven by the self-assembly of a plastic crystal phase which forms beneath the surface of the droplets.

“Plastic crystals are a special state of matter that is like the alter ego of the liquid crystals used in many TV screens,” said Smoukov. Both liquid crystals and plastic crystals can be thought of as transitional stages between liquid and solid. While liquid crystals point their molecules in defined directions like a crystal, they have no long-range order and flow like a liquid. Plastic crystals are wax-like with long-range order in their molecular arrangement, but disorder in the orientation of each molecule. ̽��ֱ��orientational disorder makes plastic crystals highly deformable, and as they change shape, the droplets change shape along with them.

“This plastic crystal phase seems to be what’s causing the droplets to change shape, or break their symmetry,” said Smoukov. “And in order to understand morphogenesis, it’s vital that we understand what causes symmetry breaking.”

̽��ֱ��researchers found that by altering the size of the droplets they started with or the rate that the temperature of the soapy solution was lowered, they were able to control the sequence of the shapes the droplets ended up forming. This degree of control could be useful for multiple applications – from pharmaceuticals to household goods – that use small-droplet emulsions.

“ ̽��ֱ��plastic crystal phase has been of intense scientific interest recently, but no one so far has been able to harness it to exert forces or show this variety of shape-changes,” said the paper’s lead author Professor Nikolai Denkov of Sofia ̽��ֱ��, who first proposed the general explanation of the observed transformations.

“ ̽��ֱ��phenomenon is so rich in combining several active areas of research that this study may open up new avenues for research in soft matter and materials science,” said co-author Professor Slavka Tcholakova, also of Sofia ̽��ֱ��.

“If we’re going to build artificial structures with the same sort of control and complexity as biological systems, we need to develop efficient bottom-up processes to create building blocks of various shapes, which can then be used to make more complicated structures,” said Smoukov. “But it’s curious to observe such life-like behaviour in a non-living thing – in many cases, artificial objects can look more ‘alive’ than living ones.”

Inset image: Morphogenesis ( ̽��ֱ�� of Cambridge).

Reference:
Denkov, Nikolai et. al. ‘Self-Shaping of Droplets via Formation of Intermediate Rotator Phases upon Cooling.’ Nature (2015). DOI: 10.1038/nature16189.

Researchers have identified a new mechanism that drives the development of form and structure, through the observation of artificial materials that shape-shift through a wide variety of forms which are as complex as those seen in nature.

It’s curious to observe such life-like behaviour in a non-living thing – in many cases, artificial objects can look more ‘alive’ than living ones

Stoyan Smoukov

̽��ֱ�� of Cambridge

Morphogenesis

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Cells cling and spiral ‘like vines’ in first 3D tissue scaffold for plants

fpjl2 — Wed, 26 Aug 2015 16:53:41 +0000

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. This environment allows scientists to observe and image individual plant cells developing in a more natural, multi-dimensional environment than previous ‘flat’ cell cultures.

̽��ֱ��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.

̽��ֱ��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.

̽��ֱ��research, conducted by a team of scientists from Cambridge ̽��ֱ��’s Sainsbury Laboratory and Department of Materials Science & Metallurgy, is published today in the open access journal BMC Plant Biology.

“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. ̽��ֱ��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.

New cost-effective material which mimics natural ‘extracellular matrix’ has allowed scientists to capture previously unseen behaviour in individual plant cells, including new shapes and interactions. New methods highlight potential developments for plant tissue engineering.

Until now, nobody had tried to put plant cells in an artificial fibre scaffold that replicates their natural environment

Raymond Wightman

Luo et al

Plant cells twisting and weaving in 3-D cultures

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

‘Pick & mix’ smart materials for robotics

sc604 — Tue, 23 Jun 2015 23:18:54 +0000

Researchers from the ̽��ֱ�� of Cambridge have developed a simple ‘recipe’ for combining multiple materials with single functions into a single material with multiple functions: movement, recall of movement and sensing – similar to muscles in animals. ̽��ֱ��materials could be used to make robotics far more efficient by replacing bulky devices with a single, smarter, life-like material. ̽��ֱ��results are published in the journal Advanced Materials.

̽��ֱ��new designer materials integrate the structure of two or more separate functions at the nanoscale, while keeping the individual materials physically separate. ̽��ֱ��gaps between the individual elements are so small that the final material is uniformly able to perform the functions of its component parts.

̽��ֱ��materials are synthesised either in a one-pot reaction, with or without solvents; or through a series of sequential reactions, where the component parts are synthesised separately one by one, and sequentially infiltrated and cross-linked at the nanoscale.

“We’re used to thinking of synthetic materials as structural, rather than functional things,” said Dr Stoyan Smoukov of the ̽��ֱ��’s Department of Materials Science and Metallurgy, who led the research. “But we’re now entering a new era of multi-functional materials, which could be considered robots themselves, since we can program them to carry out a series of actions independently.”

Smoukov’s group had previously demonstrated combined movement and muscle memory in a single material, but this is the first time that materials have been specifically designed and synthesised to perform multiple functions.

Smart polymers were first developed several decades ago, but multiple functions have not been effectively combined in the same material, since previous efforts have found that optimising one function came at the expense of the other.

In these new materials, the individual functions are integrated yet kept separate at the nanoscale. ̽��ֱ��researchers combined two different types of smart materials: an ionic electro-active polymer (i-EAP), which bends or swells with the application of voltage and are used in soft robotics; and a two-way shape memory polymer (SMP), which can be programmed to adopt and later recall specific shapes, in a type of muscle memory.

̽��ֱ��resulting combined material is what’s known as an inter-penetrated network (IPN). Due to the fact that the separate components are meshed at the nanoscale, there are unbroken paths within each component from one side of the material to the other, yet there are nanoscale boundaries between them as well. Such IPNs are highly resistant to cracks, making them very mechanically stable. Rather than stop at mechanical stability, the researchers were interested in using these structures to make multi-functional artificial muscles, which can move, sense, and also report on their environment.

̽��ֱ��movement in these hybrid materials can be controlled in several different ways, including by light, temperature, chemicals, electric field or magnetic field. These various stimuli can be used to make the materials change colour, emit light or energy, or change shape.

Making IPNs has been tried before with a type of plastic known as a block copolymer, but it has been difficult to fine-tune their exact structure because of difficult synthetic procedures. These difficulties limit the types of functionalities that can be combined, and those that are made are sometimes too costly for practical applications. In this case the researchers were able to use phase separation combined with ordinary polymer syntheses to achieve the complex structures.

According to the researchers, utilising this technique may open up a whole new avenue for smart materials, since materials that have been designed for other, single, purposes could create a large variety of multi-functional combinations. Much like choosing from an array of starters, main courses and desserts in a restaurant menu to create a multitude of dinner options, materials that perform different single functions can be combined in a mix-and-match approach to perform a myriad of tri-functional combinations. And in theory, according to the researchers, more than three intertwined components are achievable as well.

“It’s sort of like proteins, where using just 20 amino acids, you can get 8,000 different combinations of three amino acids,” said Smoukov. “Using this method, we can pick and choose from a menu of functions, and then mix them together to make materials that can do multiple things.”

̽��ֱ��capabilities of these materials could make them very useful in robotics – in fact, said Smoukov, these types of materials could even be considered robots on their own.

“We’re trying to design materials that approach the flexibility of living things,” said Smoukov. “Looking at the functionality of living things, we then want to extract that functionality and find a way to do it more simply in a synthetic material. We’re peeling back some of the layers of mystery that surround life.”

̽��ֱ��research has been funded by the European Research Council (ERC).

Researchers have successfully combined multiple functions into a single smart life-like material for the first time. These ‘designer’ materials could be used in the robotics, automotive, aerospace and security industries.

We’re peeling back some of the layers of mystery that surround life

Stoyan Smoukov

Pick and mix materials

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes