In Physics of Fluids, from AIP Publishing, University of Ottawa researchers Ezgi Pulatsu and Chibuike Udenigwe identify a range of factors that affect the print quality and shape complexity of food created with additive manufacturing. Accounting for these features can increase food quality, improve control, and speed up printing.

Additive manufacturing of food involves designing (3D shapes and their geometric codes), pre-processing (food ink preparation), manufacturing (deposition of layers to create shapes), and post-processing (baking, boiling, cooking, freezing, frying, or drying). Each step is an opportunity to create innovative foods.

Changing the printing patterns and ingredients of the initial mix or paste can affect the food’s matrix and microstructures and therefore its texture.

The flow of that mix in additive manufacturing is also crucial and is sometimes encouraged or discouraged by controlling ingredients and process conditions.

“Extrusion-based 3D printing is the most applicable technique for food,” said Pulatsu. “It involves a syringe loaded with a food paste – such as puree, dough, or frosting – being forced out of a nozzle by direct (pushing the plunger) or indirect force (compressed air).”

Creating a stable continuous flow is the first step to successful printing, so designed shapes can be produced by layering stringlike material in a controlled way.

“Once a layer is deposited, we no longer want it to flow; otherwise, it will destroy the shape we created,” said Pulatsu.

Post-processing – through baking, boiling, cooking, freezing, frying, or drying – physically and chemically transforms the food’s micro- and macromolecules and leads to various textures and tastes. At the same time, the shape should be conserved or carefully controlled.

“We also have other mechanisms of creating food structures via different 3D-printing techniques,” Pulatsu said. “For example, material jetting uses liquid binders deposited on powder to form self-supporting layers, and liquid inks that harden after deposition can also be used.”

One way to make additive manufacturing more efficient for the food industry is by establishing a printing path (a series of computer-controlled movements), which is often skipped for food applications.

“Future studies should explore the cost efficiency of different technologies in terms of build time, where shape complexity and toolpath strategies – which involve the printing path, moving head speed, and nonprinting movements – are also considered,” said Pulatsu. “Food is essential to living, and it’s becoming more critical due to the increasing global population and environmental changes. Therefore, novel foods and matrices should be designed in consultation with chefs, food scientists, and engineers, and in line with current needs.”

The results of the experiments, aided by the insights of theoretical physicists at Rutgers, could play a role in the development of revolutionary technologies and devices.

“It’s likely that that quantum materials will drive the next generation of technology and that strange metals will be part of that story,” said Piers Coleman, a Distinguished Professor at the Rutgers Center for Materials Theory in the Department of Physics and Astronomy at the Rutgers School of Arts and Sciences and one of the theoreticians involved in the study. “We know that strange metals like Y-ball exhibit properties that need to be understood to develop these future applications. We’re pretty sure that understanding this strange metal will give us new ideas and will help us design and discover new materials.”

Reporting in the journal Science, an international team of researchers from Rutgers, the University of Hyogo and the University of Tokyo in Japan, the University of Cincinnati and Johns Hopkins University described details of electron motion that provide new insight into the unusual electrical properties of Y-ball. The material, technically known as the compound YbAlB₄, contains the elements ytterbium, aluminum and boron. It was nicknamed “Y-ball” by the late Elihu Abrahams, founding director of the Rutgers Center for Materials Theory.

The experiment revealed unusual fluctuations in the strange metal’s electrical charge. The work is groundbreaking, the researchers said, because of the novel way the experimenters examined Y-ball, firing gamma rays at it using a synchrotron, a type of particle accelerator.

The Rutgers team — including Coleman, fellow physics professor Premala Chandra and former postdoctoral fellow Yashar Komijani (now an assistant professor at the University of Cincinnati) — have spent years exploring the mysteries of strange metals. They do so through the framework of quantum mechanics, the physical laws governing the realm of the ultra-small, home of the building blocks of nature such as electrons.

Analyzing the material using a technique known as Mossbauer spectroscopy, the scientists probed Y-ball with gamma rays, measuring the rate at which the strange metal’s electrical charge fluctuates. In a conventional metal, as they move, electrons hop in and out of the atoms, causing their electrical charge to fluctuate, but at a rate that is thousands of times too fast to be seen by Mossbauer spectroscopy. In this case, the change happened in a nanosecond, a billionth of a second.

“In the quantum world, a nanosecond is an eternity,” said Komijani. “For a long time, we have been wondering why these fluctuations are actually so slow.” “We reasoned,” continued Chandra, “that each time an electron hops into an ytterbium atom, it stays there long enough to attract the surrounding atoms, causing them to move in and out. This synchronized dance of the electrons and atoms slows the whole process so that it can be seen by the Mossbauer.”

They moved to the next step. “We asked the experimentalists to look for these vibrations,” said Komijani, “and to our delight, they detected them.”

Coleman explained that when an electrical current flows through conventional metals, such as copper, random atomic motion scatters the electrons causing friction called resistance. As the temperature is raised, the resistance increases in a complex fashion and at some point it reaches a plateau.

In strange metals such as Y-ball, however, resistance increases linearly with temperature, a much simpler behavior. In addition, further contributing to their “strangeness,” when Y-ball and other strange metals are cooled to low temperatures, they often become superconductors, exhibiting no resistance at all.

The materials with the highest superconducting temperatures fall into this strange family. These metals are thus very important because they provide the canvas for new forms of electronic matter — especially exotic and high temperature superconductivity.

Superconducting materials are expected to be central to the next generation of quantum technologies because, in eliminating all electrical resistance, they allow an electric current to flow in a quantum mechanically synchronized fashion. The researchers see their work as opening a door to future, perhaps unimaginable possibilities.

“In the 19th century, when people were trying to figure out electricity and magnetism, they couldn’t have imagined the next century, which was entirely driven by that understanding,” Coleman said. “And so, it’s also true today, that when we use the vague phrase ‘quantum materials,’ we can’t really envisage how it will transform the lives of our grandchildren.”

If all the lost ice was piled on London, it would stand over 2 km tall - or 7.4 times the height of the Shard. If it were to cover Manhattan, it would stand at 61 km - or 137 Empire State Buildings placed on top of one another. 

Twenty major glaciers form the Amundsen Sea Embayment in West Antarctica, which is more than four times the size of the UK, and they play a key role in contributing to the level of the world’s oceans.  

 So much water is held in the snow and ice, that if it were to all to drain into the sea, global sea levels could increase by more than one metre.  

The research, led by Dr Benjamin Davison at the University of Leeds, calculated the “mass balance” of the Amundsen Sea Embayment. This describes the balance between mass of snow and ice gain due to snowfall and mass lost through calving, where icebergs form at the end of a glacier and drift out to sea.

When calving happens faster than the ice is replaced by snowfall, then the Embayment loses mass overall and contributes to global sea level rise. Similarly, when snowfall supply drops, the Embayment can lose mass overall and contribute to sea level rise.

The results show that West Antarctica saw a net decline of 3,331 billion tonnes of ice between 1996 and 2021, contributing over nine millimetres to global sea levels.  Changes in ocean temperature and currents are thought to have been the most important factors driving the loss of ice. 

Dr Davison, a Research Fellow at the Institute for Climate and Atmospheric Science at Leeds, said: “The 20 glaciers in West Antarctica have lost an awful lot of ice over the last quarter of a century and there is no sign that the process is going to reverse anytime soon although there were periods where the rate of mass loss did ease slightly. 

“Scientists are monitoring what is happening in the Amundsen Sea Embayment because of the crucial role it plays in sea-level rise. If ocean levels were to rise significantly in future years, there are communities around the world who would experience extreme flooding.” 

The research has been published in the scientific journal Nature Communications.

Extreme snowfall events

Using climate models that show how air currents move around the world, the scientists identified that the Amundsen Sea Embayment had experienced several extreme snowfall events over the 25-year study period. 

These would have resulted in periods of heavy snowfall and periods of very little snowfall or a “snow drought.”  

The researchers factored these extreme events into their calculations. Surprisingly, they found that these events contributed up to half of the ice change at certain times, and therefore played a key role in the contribution the Amundsen Sea Embayment was making to sea level rise during certain time periods.  

For example, between 2009 and 2013, the models revealed a period of a persistant snow drought. The lack of snowfall starved the ice sheet and caused it to lose ice, therefore contributing about 25% more to sea level rise than in years of average snowfall. 

In contrast, during the winters of 2019 and 2020 there was very heavy snowfall. The scientists estimated that this heavy snowfall mitigated the sea level contribution from the Amundsen Sea Embayment, reducing it to about half of what it would have been in an average year.  

Dr Davison said: “Changes in ocean temperature and circulation appear to be driving the long-term, large-scale changes in West Antarctica ice sheet mass.  We absolutely need to research those more because they are likely to control the overall sea level contribution from West Antarctica.  

“However, we were really surprised to see just how much periods of extremely low or high snowfall could affect the ice sheet over two to five-year periods — so much so that we think they could play an important, albeit secondary role, in controlling rates of West Antarctic ice loss.” 

Dr Pierre Dutrieux, a scientist at the British Antarctic Survey and co-author of the study, added: ”Ocean temperature changes and glacial dynamics appear strongly connected in this part of the world, but this work highlights the large variability and unexpected processes by which snowfall also plays a direct role in modulating glacier mass.”

New glacier named

The ice loss from the region over the past 25 years has seen the retreat of the Pine Island Glacier,  also known as PIG.

As it retreated, one of its tributary glaciers became detached from the main glacier and rapidly accelerated. As a result, the tributary glacier has now been named by the UK Antarctic Place-names Committee, Piglet Glacier, so that it can be unambiguously located and identified by future studies.  

Dr Anna Hogg, one of the authors of the paper and Associate Professor at the Institute of Climate and Atmospheric Science at Leeds, said: “As well as shedding new light on the role of extreme snowfall variability on ice sheet mass changes, this research also provides new estimates of how quickly this important region of Antarctica is contributing to sea level rise.  

“Satellite observations have showed that the newly named Piglet Glacier accelerated its ice speed by 40%, as the larger PIG retreated to its smallest extent since records began.”  

Satellites such as the Copernicus Sentinel-1 satellite, which uses sensors that ‘see’ through cloud even during the long Polar night, have transformed our ability to monitor remote regions. It is essential to have frequent measurements of change in ice speed and iceberg calving, so that we can monitor the incredibly rapid change taking place in Antarctica.