22 Sep 2018
Ever wondered how groups of cells managed to build your tissues and organs while you were just an embryo?
Using state-of-the-art techniques he developed, UC Santa Barbara researcher Otger Campàs and his group have cracked this longstanding mystery, revealing the astonishing inner-workings of how embryos are physically constructed.
Not only does it bring a century-old hypothesis into the modern age, the study and its techniques provide the researchers a foundation to study other questions key to human health, such as how cancers form and spread or how to engineer organs.
“In a nutshell, we discovered a fundamental physical mechanism that cells use to mold embryonic tissues into their functional 3D shapes,” said Campàs, a professor of mechanical engineering in UCSB’s College of Engineering who holds the Duncan & Suzanne Mellichamp Chair in Systems Biology. His group investigates how living systems self organize to build the remarkable structures and shapes found in nature.
Cells coordinate by exchanging biochemical signals, but they also hold to and push on each other to build the body structures we need to live, such as the eyes, lungs and heart. And, as it turns out, sculpting the embryo is not far from glass molding or 3D printing. In their new work,”A fluid-to-solid jamming transition underlies vertebrate body axis elongation,” published in the journal Nature, Campàs and colleagues reveal that cell collectives switch from fluid to solid states in a controlled manner to build the vertebrate embryo, in a way similar to how we mold glass into vases or 3D print our favorite items. Or, if you like, we 3D print ourselves, from the inside.
Most objects begin as fluids. From metallic structures to gelatin desserts, their shape is made by pouring the molten original materials into molds, then cooling them to get the solid objects we use.
A fluid-to-solid jamming transition underlies vertebrate body axis elongation
As in a Chihuly glass sculpture, made by carefully melting portions of glass to slowly reshape it into life, cells in certain regions of the embryo are more active and ‘melt’ the tissue into a fluid state that can be restructured. Once done, cells ‘cool down’ to settle the tissue shape, Campàs explained.
“The transition from fluid to solid tissue states that we observed is known in physics as ‘jamming’,” Campàs said. “Jamming transitions are a very general phenomena that happens when particles in disordered systems, such as foams, emulsions or glasses, are forced together or cooled down.”
This discovery was enabled by techniques previously developed by Campàs and his group to measure the forces between cells inside embryos, and also to exert miniscule forces on the cells as they build tissues and organs. Using zebrafish embryos, favored for their optical transparency but developing much like their human counterparts, the researchers placed tiny droplets of a specially engineered ferromagnetic fluid between the cells of the growing tissue.
The spherical droplets deform as the cells around them push and pull, allowing researchers to see the forces that cells apply on each other. And, by making these droplets magnetic, they also could exert tiny stresses on surrounding cells to see how the tissue would respond.
“We were able to measure physical quantities that couldn’t be measured before, due to the challenge of inserting miniaturized probes in tiny developing embryos,” said postdoctoral fellow Alessandro Mongera, who is the lead author of the paper.
“Zebrafish, like other vertebrates, start off from a largely shapeless bunch of cells and need to transform the body into an elongated shape, with the head at one end and tail at the other,” Campàs said.
The physical reorganization of the cells behind this process had always been something of a mystery. Surprisingly, researchers found that the cell collectives making the tissue were physically like a foam (yes, as in beer froth) that jammed during development to ‘freeze’ the tissue architecture and set its shape.
These observations confirm a remarkable intuition made by Victorian-era Scottish mathematician D’Arcy Thompson 100 years ago in his seminal work “On Growth and Form.”
Read About: D’Arcy Wentworth Thompson
“He was convinced that some of the physical mechanisms that give shapes to inert materials were also at play to shape living organisms. Remarkably, he compared groups of cells to foams and even the shaping of cells and tissues to glassblowing,” Campàs said. A century ago, there were no instruments that could directly test the ideas Thompson proposed, Campàs added, though Thompson’s work continues to be cited to this day.
The new Nature paper also provides a jumping-off point from which the Campàs Group researchers can begin to address other processes of embryonic development and related fields, such as how tumors physically invade surrounding tissues and how to engineer organs with specific 3D shapes.
“One of the hallmarks of cancer is the transition between two different tissue architectures. This transition can in principle be explained as an anomalous switch from a solid-like to a fluid-like tissue state,” Mongera explained. “The present study can help elucidate the mechanisms underlying this switch and highlight some of the potential druggable targets to hinder it.”
Alessandro Mongera, Payam Rowghanian, Hannah J. Gustafson, Elijah Shelton, David A. Kealhofer, Emmet K. Carn, Friedhelm Serwane, Adam A. Lucio, James Giammona & Otger Campàs
22 Sep 2018
Lithium-based battery could make use of greenhouse gas before it ever gets into the atmosphere.
A new type of battery developed by researchers at MIT could be made partly from carbon dioxide captured from power plants. Rather than attempting to convert carbon dioxide to specialized chemicals using metal catalysts, which is currently highly challenging, this battery could continuously convert carbon dioxide into a solid mineral carbonate as it discharges.
While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.
The battery is made from lithium metal, carbon, and an electrolyte that the researchers designed. The findings are described today in the journal Joule, in a paper by assistant professor of mechanical engineering Betar Gallant, doctoral student Aliza Khurram, and postdoc Mingfu He.
Currently, power plants equipped with carbon capture systems generally use up to 30 percent of the electricity they generate just to power the capture, release, and storage of carbon dioxide. Anything that can reduce the cost of that capture process, or that can result in an end product that has value, could significantly change the economics of such systems, the researchers say.
However, “carbon dioxide is not very reactive,” Gallant explains, so “trying to find new reaction pathways is important.” Generally, the only way to get carbon dioxide to exhibit significant activity under electrochemical conditions is with large energy inputs in the form of high voltages, which can be an expensive and inefficient process. Ideally, the gas would undergo reactions that produce something worthwhile, such as a useful chemical or a fuel. However, efforts at electrochemical conversion, usually conducted in water, remain hindered by high energy inputs and poor selectivity of the chemicals produced.
Gallant and her co-workers, whose expertise has to do with nonaqueous (not water-based) electrochemical reactions such as those that underlie lithium-based batteries, looked into whether carbon-dioxide-capture chemistry could be put to use to make carbon-dioxide-loaded electrolytes — one of the three essential parts of a battery — where the captured gas could then be used during the discharge of the battery to provide a power output.
This approach is different from releasing the carbon dioxide back to the gas phase for long-term storage, as is now used in carbon capture and sequestration, or CCS. That field generally looks at ways of capturing carbon dioxide from a power plant through a chemical absorption process and then either storing it in underground formations or chemically altering it into a fuel or a chemical feedstock.
Instead, this team developed a new approach that could potentially be used right in the power plant waste stream to make material for one of the main components of a battery.
While interest has grown recently in the development of lithium-carbon-dioxide batteries, which use the gas as a reactant during discharge, the low reactivity of carbon dioxide has typically required the use of metal catalysts. Not only are these expensive, but their function remains poorly understood, and reactions are difficult to control.
By incorporating the gas in a liquid state, however, Gallant and her co-workers found a way to achieve electrochemical carbon dioxide conversion using only a carbon electrode. The key is to pre-activate the carbon dioxide by incorporating it into an amine solution.
“What we’ve shown for the first time is that this technique activates the carbon dioxide for more facile electrochemistry,” Gallant says. “These two chemistries — aqueous amines and nonaqueous battery electrolytes — are not normally used together, but we found that their combination imparts new and interesting behaviors that can increase the discharge voltage and allow for sustained conversion of carbon dioxide.”
They showed through a series of experiments that this approach does work, and can produce a lithium-carbon dioxide battery with voltage and capacity that are competitive with that of state-of-the-art lithium-gas batteries. Moreover, the amine acts as a molecular promoter that is not consumed in the reaction.
The key was developing the right electrolyte system, Khurram explains. In this initial proof-of-concept study, they decided to use a nonaqueous electrolyte because it would limit the available reaction pathways and therefore make it easier to characterize the reaction and determine its viability. The amine material they chose is currently used for CCS applications, but had not previously been applied to batteries.
This early system has not yet been optimized and will require further development, the researchers say. For one thing, the cycle life of the battery is limited to 10 charge-discharge cycles, so more research is needed to improve rechargeability and prevent degradation of the cell components. “Lithium-carbon dioxide batteries are years away” as a viable product, Gallant says, as this research covers just one of several needed advances to make them practical.
But the concept offers great potential, according to Gallant. Carbon capture is widely considered essential to meeting worldwide goals for reducing greenhouse gas emissions, but there are not yet proven, long-term ways of disposing of or using all the resulting carbon dioxide. Underground geological disposal is still the leading contender, but this approach remains somewhat unproven and may be limited in how much it can accommodate. It also requires extra energy for drilling and pumping.
The researchers are also investigating the possibility of developing a continuous-operation version of the process, which would use a steady stream of carbon dioxide under pressure with the amine material, rather than a preloaded supply the material, thus allowing it to deliver a steady power output as long as the battery is supplied with carbon dioxide. Ultimately, they hope to make this into an integrated system that will carry out both the capture of carbon dioxide from a power plant’s emissions stream, and its conversion into an electrochemical material that could then be used in batteries. “It’s one way to sequester it as a useful product,” Gallant says.
“It was interesting that Gallant and co-workers cleverly combined the prior knowledge from two different areas, metal-gas battery electrochemistry and carbon-dioxide capture chemistry, and succeeded in increasing both the energy density of the battery and the efficiency of the carbon-dioxide capture,” says Kisuk Kang, a professor at Seoul National University in South Korea, who was not associated with this research.
“Even though more precise understanding of the product formation from carbon dioxide may be needed in the future, this kind of interdisciplinary approach is very exciting and often offers unexpected results, as the authors elegantly demonstrated here,” Kang adds.
MIT’s Department of Mechanical Engineering provided support for the project.
** See Comprehensive Guide provided by Paul Martin at the conclusion of this Post.
“There are many things which can go wrong when starting a company; but the worst thing that can go wrong is to not do it,” said Prof. Karl Leo, Director of KAUST’s Solar & Photovoltaics Engineering Research Center, when speaking at an Entrepreneurship Center speaker series event this past spring. Wearing the dual hats of scientist and entrepreneur, Prof. Leo is the author of 440 publications, holds more than 50 patents, and has co-created 8 companies which have generated over 300 jobs.
A physicist by training, Prof. Leo highlighted the point that he is primarily a scientist who stumbled onto business by chance. “For me it’s always started with and been about the science,” he says. All his spin-off companies came about as a result of basic research he and his group conducted on organic semiconductors. Speaking specifically to the young KAUST researchers hoping to emulate his success as academics and entrepreneurs, Prof. Leo said: “The message I want to pass along is if you really want to do things, just be curious. Don’t say I want to do research to make a company. Do very basic research and the spin-off ideas will come along.”
The Growing Influence of Organic Semiconductors
Prof. Karl Leo started doing research on organic semiconductors about 20 years ago. He has since been passionate about this field’s developments and future potential. Despite his early skepticism resulting from the ephemeral lifetime of organic semiconductors in the ’90s, the performance levels of LED devices for instance have gone from just a few minutes of useful life then to virtually not aging today. “In the long-term, as in 20 to 30 years from now, almost everything will be organics,” he believes. “Silicon has dominated electronics for a long time but organic is something new.” Organic products have evolved into a variety of applications such as: small OLED displays, OLED televisions, OLED lighting, OPV and organic electronics.
Organics, as opposed to traditional silicon-based semiconductors, are by nature essentially lousy semiconductors. Mobility, or the speed at which electrons move on these materials, is a really important property. However, when looking at the electronic properties of semiconductors, carbon offers interesting developments for the performance of organics. For instance, graphene, which is a carbon-based organic material, has even higher mobility than silicon.
One of the companies Prof. Karl Leo co-founded and began operating out of Dresden, Germany in 2003, Novaled, became a leader in in organic light-emitting diode (OLED) field. OLEDs are made up of multiple thin layers of organic materials, known as OLED stacks. They essentially emit light when electricity is applied to them. Novaled became a pioneer in developing highly efficient and long-lifetime OLED structures; and it currently holds the world record in power efficiency. They key to Novaled’s success, as Prof. Leo explains, is “the simple discovery that you can dope organics.” This was a major breakthrough achieved simply adding a very little amount of another molecule.
This organic conductivity doping technology, used to enhance the performance of OLED devices, was the main factor leading to the company being purchased by Samsung in 2013.
Organic Photovoltaics: Technology of the Future
Following the successful commercial penetration of OLED displays in the consumer electronics market, Prof. Karl Leo has since turned his focus on organic photovoltaics. “I think organic PV is something that can change the world,” said Leo. Among the many advantages of organic photovoltaics are that they are thin organic layers which can be applied on flexible plastic substrates. They consume little energy, can be made transparent, and are compatible with low-cost large-area production technologies. Because they are transparent, they can be made into windows for instance, and also be manufactured in virtually any color. All these characteristics make organic PV ideal for consumer products.
Again based on basic research conducted by his group, Prof. Leo also started a company, Heliatek, which is now a world-leader in the production of organic solar film. Heliatek has developed the current world record in the efficiency of transparent solar cells. The company also holds the record for efficiency of opaque cells at 12 percent. Leo believes that it’s possible to achieve up to 20 percent efficiency in the near future, which will be necessary to compete with silicon and become commercially viable.
Don’t Believe Business Plans
Prof. Leo explained that the experience he and his team gained from launching a successful company like Novaled helped them to both define the objectives and obtain funding from investors for his solar cell company, Heliatek. “Once you create a successful company, things get much easier,” he said. But Leo also cautioned the budding entrepreneurs in the audience to be willing to adapt as they present and implement their ideas.
“If you have a good idea and you are convinced you have a good idea, never give up,” he said. But being able to adapt to market needs is also crucial. For instance, Leo’s original business plan for Novaled focused on manufacturing displays. But the realities of the market, and the prohibitive cost of manufacturing displays, convinced his team that the smarter way to go was to supply materials. At the end of the day, what really succeeded in getting a venture capital firm’s attention, after haven been told no 49 times, was his team’s ability to demonstrate the value of the technology.
“Business plans are useful but they must not be overestimated,” said Prof. Leo. Business plans are a good indicator of how entrepreneurs are able to structure their thoughts, identify markets and create a roadmap, but “nobody is able to predict the future in a business plan; it’s not possible.”
Definition of Organic Semi-Conductors: Background
An organic semiconductor is an organic material with semiconductor properties, that is, with an electrical conductivity between that of insulators and that of metals. Single molecules, oligomers, and organic polymers can be semiconductive. Semiconducting small molecules (aromatic hydrocarbons) include the polycyclic aromatic compounds pentacene, anthracene, and rubrene.Polymeric organic semiconductors include poly(3-hexylthiophene), poly(p-phenylene vinylene), as well as polyacetyleneand its derivatives.
There are two major overlapping classes of organic semiconductors. These are organic charge-transfer complexes and various linear-backbone conductive polymers derived from polyacetylene. Linear backbone organic semiconductors include polyacetylene itself and its derivatives polypyrrole, and polyaniline.
At least locally, charge-transfer complexes often exhibit similar conduction mechanisms to inorganic semiconductors. Such mechanisms arise from the presence of hole and electron conduction layers separated by a band gap.
Although such classic mechanisms are important locally, as with inorganic amorphous semiconductors, tunnelling, localized states, mobility gaps, and phonon-assisted hopping also significantly contribute to conduction, particularly in polyacetylenes. Like inorganic semiconductors, organic semiconductors can be doped. Organic semiconductors susceptible to doping such as polyaniline (Ormecon) and PEDOT:PSS are also known as organic metals
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