“There is much noise about the direct effects of agrochemicals on pollinators, a subject of profound societal attention, but it now emerges that ozone is a silent threat to pollinators and thus pollination,” says lead author Evgenios Agathokleous, an ecologist at Nanjing University of Information Science & Technology. “These impacts of ozone have long been missed.”

Ozone gas can be both friend and foe to the planet. In the stratosphere, 12 kilometers above sea level, ozone forms naturally and helps protect the Earth from harmful sun rays. But below that zone, ozone is a damaging pollutant. Tropospheric-level ozone gas is created by a photochemical reaction between volatile organic compounds — emitted by vegetation and commonly found in substances such as paint and aerosols — and oxides of nitrogen, which are released when fossil fuels burn. Tropospheric ozone levels have been rising because a warming climate is creating optimal conditions for its formation.

“Ozone pollution can affect the timing and duration of flowering in such a way that the occurrence of flowering is asynchronous to the activities of pollinators,” says Agathokleous. “It can also change the color of flowers, disrupting the visual signals to pollinators. Ozone pollution can also directly react with pollen, decreasing its quality, but also indirectly changing the amount of pollen.”

Ozone pollution can also damage plant leaves almost instantly, leaving injury signs of diverse colors and shapes and discoloring leaves. When damaged, leaves have a hard time photosynthesizing and struggle to provide the plant with the energy it needs to grow. Plants emit their own organic volatile compounds that act as chemical signals facilitating communication from one plant to another and alert pollinators to the presence of a waiting flower. Ozone pollution appears to be disrupting these chemical signatures.

“Changes in the composition of the volatile blends could also have severe implications to pollinators because they might not recognize host plants and their qualities in the same way they did in the past,” says Agathokleous. “Within plant tissues, ozone pollution could decrease the amount of nutrients that are essential to insects, increase the abundance of chemicals that are harmful to insects ingesting them, and degrade the overall quality of plant tissues.”

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Materials provided by Cell Press. Note: Content may be edited for style and length.

The breakthrough could be a potential game-changer for manufacturing customized chip-based microelectromechanical systems (MEMS). These mini-machines are mass-produced in large volumes for hundreds of electronic products, including smartphones and cars, where they provide positioning accuracy. But for more specialized manufacturing of sensors in smaller volumes, such as accelerometers for aircraft and vibration sensors for industrial machinery, MEMS technologies demand costly customization.

Frank Niklaus, who led the research at KTH Royal Institute of Technology in Stockholm, says the new 3D printing technique, which was published in Nature Microsystems & Nanoengineering, provides a way to get around the limitations of conventional MEMS manufacturing.

“The costs of manufacturing process development and device design optimizations do not scale down for lower production volumes,” he says. The result is engineers are faced with a choice of suboptimal off-the-shelf MEMS devices or economically unviable start-up costs.

Other low-volume products that could benefit from the technique include motion and vibration control units for robots and industrial tools, as well as wind turbines.

The researchers built on a process called two-photon polymerization, which can produce high resolution objects as small as few hundreds of nanometers in size, but not capable of sensing functionality. To form the transducing elements, the method uses a technique called shadow-masking, which works something like a stencil. On the 3D-printed structure they fabricate features with a T-shaped cross-section, which work like umbrellas. They then deposit metal from above, and as a result, the sides of the T-shaped features are not coated with the metal. This means the metal on the top of the T is electrically isolated from the rest of the structure.

With this method, he says it takes only few hours to manufacture a dozen or so custom designed MEMS accelerometers using relatively inexpensive commercial manufacturing tools. The method can be used for prototyping MEMS devices and manufacturing small- and medium-sized batches of tens of thousands to a few thousand MEMS sensors per year in an economically viable way, he says.

“This is something that has not been possible until now, because the start-up costs for manufacturing a MEMS product using conventional semiconductor technology are on the order of hundreds of thousands of dollars and the lead times are several months or more,” he says. “The new capabilities offered by 3D-printed MEMS could result in a new paradigm in MEMS and sensor manufacturing.

“Scalability isn’t just an advantage in MEMS production, it’s a necessity. This method would enable fabrication of many kinds of new, customized devices.”

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Materials provided by KTH, Royal Institute of Technology. Original written by David Callahan. Note: Content may be edited for style and length.

This is why research teams from TU Wien and the Fritz Haber Institute in Berlin have developed a novel approach that allows to have “triple eyes” on a catalytic reaction — using three different surface microscopies. This way, they were able to show that during the catalytic conversion of hydrogen and oxygen to water, reaction fronts on the crystal surface not only form remarkable geometric patterns, but also a new mechanism of the propagation of these fronts was discovered. Especially for climate-relevant technologies such as ecologically clean hydrogen-based energy production, a comprehensive understanding of such processes is crucial.

Different measurements in a single instrument

“Many scientific questions can only be answered by combining different microscopy methods on the same sample, which is called correlative microscopy,” says Prof. Günther Rupprechter from the Institute of Materials Chemistry at TU Wien. “However, this usually comes with limitations.” You have to remove a sample from one instrument and perform the same experiment again in another microscope. Often, for methodological reasons, the experimental conditions are then completely different — some measurements take place in a vacuum, others in air. Often temperatures are different. In addition, you may not be looking at the same spot on the sample with different instruments — this can also influence the results. Thus, it is difficult to combine the results of different measurements in a reliable way.

Ultraviolet, X-rays and electrons

Now, however, it has been possible to combine three different microscopies in a way that the same spot on the same sample was examined under the same environmental conditions. Three different electron microscopies were used: two different variants of photoemission electron microscopy (PEEM), namely UV-PEEM and X-PEEM, and low energy electron microscopy (LEEM).

In UV-PEEM and X-PEEM, the sample surface is illuminated with ultraviolet light and X-rays, respectively. In both cases, it results in electrons being emitted from the surface. Similar to how light beams are focused in an optical microscope, the electron beams form a real-time image of the surface and of the processes taking place there. In an X-PEEM, one can additionally filter the emitted electrons according to their energies and thereby determine the chemical composition of the sample surface. Access to the necessary high-energy, high-intensity X-rays was provided to the research team by the Berlin synchrotron (HZB BESSY II). In the LEEM technique, the surface is irradiated with an electron beam. The electrons that are backscattered from the surface create the real time image of the sample surface and of the ongoing processes, such as a catalytic reaction.

Since all three microscopies use different imaging mechanisms, this allowed to study different aspects of catalytic hydrogen oxidation on a structurally identical site of the sample , says Prof. Yuri Suchorski, who has been involved in surface microscopy since 1974. “In addition, the X-PEEM technique provides chemical contrast and therefore allows us to correlate the pattern formation on the surface with the chemical composition of the surface and the reactants present on the surface, hence the term correlative microscopy.”

Watching how hydrogen oxidizes to water

Thus, it became possible to study the oxidation of hydrogen on structurally well-defined microscopic regions of a rhodium foil (structure determination by researchers at USTEM of TU Wien) in a versatile way and in real time.

The reaction spreads over the surface like a wave, revealing a new kind of pattern formation that had never been encountered before. “In front of the spreading reaction front, new small islands of catalytically active areas form, accelerating the propagation of the reaction,” says Prof. Rupprechter. In computer simulations that provide virtual reaction microscopy, the team was able to model and explain the formation of these islands.

Through the correlative approach, it was now possible to effectively use the specific strength of each of the respective microscopy methods (spatial and energy resolution, field of view, magnification down to the nanometer range), and thus to image an ongoing catalytic reaction in unprecedented detail.

The oxidation of hydrogen to water by solid catalysts is one of the significant processes that enable energy generation without combustion and without pollution (the exhaust gas consists of pure water), e.g., in fuel cells. For future developments of new green energy production technologies, it will be important to watch ongoing catalytic reactions at work with several eyes in order to deeply understand fine details of the catalytic processes.