The Hintereisferner, located at the back of the Tyrolean Ötztal, has been closely monitored for more than 100 years, and there have been continuous records of its mass balance since 1952. This makes it one of the best-studied glaciers in the Alps and has been key to glacier and climate research at the University of Innsbruck for decades. Since 2016, the researchers have also been surveying the glacier with a worldwide unique system: the surface of the glacier is scanned daily with a terrestrial laser scanner returning the glacier surface elevation changes. This way, the change in the volume of the Hintereisferner is monitored in real time. Innsbruck glaciologist Annelies Voordendag led the measurement on site at the Hintereisferner, the results of the researchers’ investigations have now been published as highlighted article in the journal The Cryosphere.

“Already in the early summer of 2022, it became clear that the day when the ice the glacier gained during the winter starts melting away would be reached very soon. We call this day the ‘Glacier Loss Day’ or GLD for short. It can be compared to the Earth Overshoot Day, which marks the date when we use up more natural resources than the Earth can renew in a year,” explains Annelies Voordendag. Monitoring a glacier’s volume and mass alterations on a daily basis provides a quick assessment of its condition in a given year.

Observing glaciers’ health

When the GLD arrives, it means the glacier is no longer in balance with the natural conditions for that year. The earlier the GLD happens, the more time is left in the remaining summer that the glacier likely will lose volume and thus, mass. “We track the daily volume changes with the automated terrestrial laser scanninng setup overlooking the glacier and derive the day that the mass gained during winter has been lost,” says Voordendag. In 2022 the GLD was measured on the 23rd of June. In the two previous years, Glacier Loss Day was reached only in the middle of August.

Also in years with negative balance extremes — such as 2003 and 2018 — this day was not reached until the end of July. Even if not every summer in the future will necessarily be like the one in 2022, the trend is clear for the glaciologists, because the developments lie outside normal fluctuation ranges: “These are clear signals of anthropogenic climate change. The consequences of our greenhouse gas emissions are already hitting us hard today,” adds glaciologist Rainer Prinz from the “Ice and Climate” working group in Innsbruck. The future projections of development do not present an encouraging outlook either. Only half of the Hintereisferner will be left in 10 to 20 years,” the team summarizes in their study. These are clear climate change signals that are due to anthropogenic global warming and the consequences of our greenhouse gas emissions, which are already fully affecting us today.”

Led by Professor Dong Woog Lee from the School of Energy and Chemical Engineering at UNIST, the research team developed novel crosslinkers utilizing m-xylylene diisocyanate (XDI) or 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) as hard segments along with poly(ethylene glycol) (PEG) groups serving as soft segments. By incorporating these newly synthesized materials into pressure-sensitive adhesives, they achieved significantly improved recoverability compared to traditional methods.

The PSA formulated with H6XDI-PEG diacrylate (HPD) demonstrated exceptional recovery properties while maintaining high adhesion strength (~25.5 N 25 mm?1). Through extensive folding tests totaling 100k folds and multi-directional stretching tests spanning 10k cycles, the PSA crosslinked with HPD exhibited remarkable stability under repeated deformation — showcasing its potential for applications requiring both flexibility and recoverability.

Furthermore, even after subjecting the adhesive to strains up to 20%, it displayed high optical transmittance (>90%), making it suitable for fields such as foldable displays that demand not only flexibility but also optical clarity.

“This breakthrough in adhesive technology offers promising possibilities for electronic products that require both high flexibility and rapid recovery characteristics,” said Professor Lee. “Our research addresses the long-standing challenge of balancing adhesion strength and resilience, opening up new avenues for the development of flexible electronic devices.”

Hyunok Park, a researcher involved in the study, emphasized the significance of this research by stating, “The introduction of this new crosslinking structure has led to an adhesive with exceptional adhesion and recovery properties. We believe it will drive future advancements in adhesive research while contributing to further developments in flexible electronics.”

The study findings have been published ahead of their official publication in the online version of Advanced Functional Materials on July 12, 2023. This work was supported through the 2023 Research Fund at UNIST and received additional support from organizations including the National Research Foundation (NRF) of Korea, Defense Acquisition Program Administration and Ministry of Trade.

To meet these demands, the industry must look beyond silicon to produce devices appropriate for the growing role of computing.

While unlikely to abandon the workhorse material anytime in the near or distant future, the technology sector will require creative enhancements in chip materials and architectures to produce devices appropriate for the growing role of computing.

One of the biggest shortcomings of silicon is that it can only be made so thin because its material properties are fundamentally limited to three dimensions [3D]. For this reason, two-dimensional [2D] semiconductors — so thin as to have almost no height — have become an object of interest to scientists, engineers and microelectronics manufacturers.

Thinner chip components would provide greater control and precision over the flow of electricity in a device, while lowering the amount of energy required to power it. A 2D semiconductor would also contribute to keeping the surface area of a chip to a minimum, lying in a thin film atop a supporting silicon device.

But until recently, attempts to create such a material have been unsuccessful.

Certain 2D semiconductors have performed well on their own, but required such high temperatures to deposit they destroyed the underlying silicon chip. Others could be deposited at silicon-compatible temperatures, but their electronic properties — energy usage, speed, precision — were lacking. Some fit the bill for temperature and performance but could not be grown to the requisite purity at industry-standard sizes.

Now, researchers at the University of Pennsylvania School of Engineering and Applied Science have grown a high-performing 2D semiconductor to a full-size, industrial-scale wafer. In addition, the semiconductor material, indium selenide (InSe), can be deposited at temperatures low enough to integrate with a silicon chip.

Deep Jariwala, Associate Professor and Peter and Susanne Armstrong Distinguished Scholar in the Department of Electrical and Systems Engineering (ESE), and Seunguk Song, postdoctoral fellow in ESE, led the study, published recently in Matter.

“Semiconductor manufacturing is an industrial-scale manufacturing process,” says Jariwala. “You aren’t going to have a viable material unless you can produce it on industrial-scale wafers. The more chips you can make in a batch, the lower the price. But the material must also be pure to ensure performance. This is why silicon is so prevalent — you can make it in large quantities without sacrificing purity.”

InSe has long shown promise as a 2D material for advanced computing chips because it carries electrical charge exceptionally well. But producing large enough films of InSe has proven tricky because the chemistry of indium and selenium tends to combine in a few different molecular proportions, taking on chemical structures with varying ratios of each element and thus compromising its purity.

The team’s success hinged on Song’s application of a growth technique that overcame the quirks of InSe’s atomic structure.

“For the purposes of an advanced computing technology, the chemical structure of 2D InSe needs to be exactly 50:50 between the two elements. The resulting material needs a uniform chemical structure over a large area to work,” says Song.

The team achieved this groundbreaking purity using a growth technique called “vertical metal-organic chemical vapor deposition” (MOCVD). Previous research had attempted to introduce the indium and selenium in equal quantities and at the same time. Song demonstrated, however, that this method was the source of undesirable chemical structures in the material, producing molecules with varying ratios of each element. MOCVD, by contrast, works by sending the indium in a continuous stream while introducing the selenium in pulses.

“By pulsing, you give the indium and selenium time to combine. In the moments between pulses, you deprive the environment of selenium, which prevents the ratio from getting too high. The benefit of the pulse is the pause. That’s how we get a uniform 50:50 ratio across our entire full-size wafer,” says Song.

In addition to chemical purity, the team was also able to control and align the direction of crystals in the material, enhancing the quality of their semiconductor even further by providing a seamless environment for electron transport.

“The two most important material qualities in a semiconductor are chemical purity and crystalline order. The most important industrial quality is scalability. This material checks every box,” says Jariwala.

Eastern hemlocks are an ecologically important tree species found from eastern Canada to the Great Lakes states and south along the entire Appalachian mountain range. The hemlock woolly adelgid — an invasive insect that was introduced to North America 70 years ago and has spread along the East Coast — can kill a hemlock tree in as little as four years.

“An integrated pest management strategy is the best approach in cases like this,” says Robert Jetton, associate professor of forest health at North Carolina State University and study co-author. “Integrated pest management utilizes multiple tactics to combat insect pests and can include chemical insecticides, seed preservation, biological control, and silviculture, or managing the surrounding forest.

“This study focused on silviculture. Is there a way to actively manage a forest to improve the health of eastern hemlocks?”

The study began in 2017. Jetton and colleagues from the U.S. Department of Agriculture selected 105 eastern hemlock trees in national and state forests along the Appalachians from Maryland to Georgia. They created small or large canopy gaps around the trees by either felling or girdling the competing trees. Felling is cutting down the tree outright, while girdling refers to killing the tree by removing its access to nutrients, but not cutting it down.

The gaps around the hemlocks ranged in size from .05 to .15 acre. Small gaps were created by felling or girdling any competing tree that overlapped the hemlock’s outermost branches, or dripline. For large gaps, they created a radius around the hemlock that was equal to the dripline plus 25% of the average tree height in the stand.

For comparison, the researchers also monitored a control group which consisted of hemlocks that didn’t have canopy gaps created around them.

The researchers collected data on the trees every six months from late 2017 through early 2021. One tree had died (due to another tree falling on it), but overall, even though all of the “canopy gap” trees in the study were infested with woolly adelgid, their health had substantially improved. By comparison, the health of the control trees continued to decline.

“The major benefit of the treatment is that the trees’ crown health improved, especially in areas where we did the large fell,” Jetton says. “Crown health refers to the tree’s foliage — its color and density. With all four gap treatments, we saw that the trees continued to produce new shoot growth annually, though this effect was greatest in the large fells. This is good news because woolly adelgids feed on branch tips, so one of the first effects of infestation is that the tree stops producing new growth.”

While the treatment’s effectiveness varied by region — it was more effective in the southernmost sites (North Carolina, Georgia and Tennessee) — the researchers believe the results are encouraging.

“The canopy gaps give the trees better access to resources like water and nutrients that help them deal with the adelgid,” Jetton says. “While it doesn’t cause the adelgid population to decrease, it may be giving trees the ability to ‘outgrow’ the insect’s impact, at least temporarily.”

The study is ongoing, and the researchers plan to focus on stands of hemlocks, rather than single trees, next.

“Our study was conducted in forests where hemlocks occurred under a canopy of primarily hardwood trees, which lose their leaves in fall and winter,” says Albert Mayfield, entomologist with the USDA Forest Service and study co-author. “So, the response of hemlocks to canopy gaps might be different in pure hemlock forests, where there is more year-round shade. But our sites were very typical of the southern Appalachian forests, where hemlock trees are usually mixed with hardwood trees.”

“We see silviculture as part of the overall pest management strategy,” says Jetton. “Hopefully it will benefit biological control efforts by allowing the adelgid’s predators to establish populations, and it may decrease our use of chemicals. But the bottom line is this study shows silviculture is another tool in the toolkit to increase the survival rate of eastern hemlocks.”

The study appears in Forest Ecology and Management and was supported by the USDA Forest Service Special Technology Development Program. Albert Mayfield of the USDA Forest Service is corresponding author. NC State research associate Andy Whittier, and USDA Forest Service members Bryan Mudder, Tara Keyser, and James Rhea, also contributed to the work.