High-performance SEM drives plant and food research

Plant & Food Research Rangahau Ahumāra Kai — a New Zealand Government-owned research institute — is on a mission to improve the way food is grown, harvested, prepared and shared, and electron microscopy is a pivotal technology leveraged by the Microscopy and Imaging team in their research.

The team’s electron microscopy capabilities have now been improved with the installation of a TESCAN CLARA scanning electron microscope (SEM) with STEM (scanning transmission electron microscope) and EDS (energy dispersive X-ray spectroscopy) detectors in their microscopy facility in Auckland. This new instrument has consolidated all their electron microscopy requirements into a single instrument as well as opening up new possibilities.

The TESCAN CLARA is a field-emission ultrahigh-resolution SEM that is designed to image conductive, non-conductive and magnetic samples, making it suitable for imaging and analysis of a wide variety of materials. The system specifically came equipped with cryogenic and variable pressure imaging capabilities along with EDS for elemental analysis and mapping.

“When we decided to replace our aging SEM and TEM, the TESCAN CLARA with STEM detector ticked all the boxes,” said Ria Rebstock, Microscopy and Imaging team leader. “The increase in SEM resolution allows us to easily observe structures and answer questions we couldn’t previously.

“Using TESCAN’s BrightBeam column and beam deceleration technology enables us to image biological samples that would otherwise need coating to avoid charging, allowing us to accurately measure microscopic features such as nanocracks in starch. The addition of EDS has added new capability, which we have already leveraged for our own research, commercial clients and industry partners. The EDS software is seamlessly integrated in the TESCAN user interface and caters to beginners and experts alike.”

Images generated by Plant & Food Research using the TESCAN CLARA. (A) Aeromicropylar structures found on stink bug egg lids. (B) TEM-like image of plant meristem cells taken in inverted contrast backscatter electron mode. (C) Leaf fracture cross-section obtained via cryo-SEM. (D) Copper sulfide microballs precipitated in wood tissue.

“The instrument is so easy to use, and I have been able to customise TESCAN’s Essence user interface streamlining our workflow,” added Andrew Chan, research scientist and primary instrument operator. “New users can easily be trained to operate the CLARA in less than an hour, even people with no prior SEM experience.

“We have already had success imaging a diverse range of specimens as part of our research, including plant material such as fruit skins, stems, leaves, microorganisms such as fungi, bacteria and viruses, insects and fish. We’ve also improved the reliability of our workflows for producing TEM-like images using the retractable four quadrant BSE (backscattered electron) detector.

“While the sample preparation process remains largely the same, we now use robust silicon wafers instead of delicate copper or nickel grids to mount sections. We then detect backscattered electrons, which provides a TEM-like image when the contrast is inverted. Using this technique, we no longer contend with grid bars obscuring parts of our sample!”

AXT is TESCAN’s distributor in New Zealand. The company’s Managing Director, Richard Trett commented, “To date, most TESCAN CLARAs are being used to characterise materials. It is exciting to see how truly versatile this SEM is, and how Plant & Food Research have used it so successfully to image biological specimens. It is equally as exciting to see how they have been able to harness the improved imaging capabilities of the system so quickly and we look forward to seeing their applied research being published in the near future.”

Top image shows the Microscopy and Imaging team: Ian Hallett, Ria Rebstock, Andrew Chan and Nicola Shaw.