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University of Ghent, Belgium applies cryo prep techniques to prepare food samples for SEM

The challenge of imaging using scanning electron microscopy (SEM) is the ability to keep samples in their natural state, hence the requirement to employ cryo sample prep and the selection of Quorum's PP3000T system for the task.

Ir Davy Van de Walle is a senior researcher in the Laboratory of Food Technology & Engineering at the University of Ghent. He works for the head of the laboratory, Professor Koen Dewettinck. Their mission is to design foods on the nano- and microscale, which provide the answer to the consumer demand for new products that are tasty, satisfying, healthy, convenient and inexpensive to produce. Moreover, this may create added value to by-products and contribute to overall socio-economic welfare. Put more simply, they want to understand how ingredient interactions and processing affect the quality attributes (texture, mouthfeel and taste among others) of foods (dairy products, margarines/shortenings and chocolate products in particular). 

Mr Van de Walle describes the background and execution of the imaging process in detail: “Because a field emission gun (FEG) is used in high resolution SEM, it needs to be placed in an ultra-high vacuum of 10-7 to 10-8 Pa. Consequently, these extreme vacuum conditions require that the specimen must not release any gas or vapour when inserted into the SEM. Except for powdered foods such as flour, sugar or milk powder, most foods contain water. Scanning electron microscopes at lower vacuum conditions (Low-Vacuum SEM, Variable Pressure SEM and Environmental SEM) can be used to examine wet, oily and non-conductive samples in their natural state. In this way, there is no need to dry or freeze the specimen. This is particularly useful with fragile food samples. However, cryo-SEM is the most appropriate technique in food research because of its extremely high resolution. 

The goal of the cryo-SEM is to vitrify the liquid phase with all the constituents, i.e. macromolecules, thus preserving them in their natural and original state. This process is achieved with the use of the Quorum PP3000T cryo sample preparation system. The initial rapid cooling of the sample is the most critical part in the use of the cryo-SEM system. A slush of liquid N2 (-210 °C) is used for the fast freezing to minimize any damage ice crystals may cause. Following, the sample is transferred under vacuum to the cold stage of the preparation chamber, which is mounted on the SEM chamber. The sample can be fractured to expose internal microstructure, etched to reveal greater detail and coated with metal (e.g. Pt) by sputtering. Finally, the sample is transferred into the SEM chamber where it is mounted on a cold stage specifically tailored to the SEM.” 

Describing the background to choosing the Quorum sample preparation system, Mr Van de Walle said the process followed a tender procedure involving several FEG-SEM vendors. “Several companies (e.g. Jeol and Hitachi) offered their FEG-SEM in combination with the Quorum preparation chamber. During our meetings with these suppliers, they recommended Quorum as being the best performing. We have been very satisfied with our choice and the group has started to publish papers where the cryo prep system has been invaluable. One example is the PhD research1 of Dr Phuong Diem Tran in which the applicability of cryo-SEM for storage stability testing of pralines is reported. These pralines suffered from fat and sugar bloom. These phenomena are illustrated in the images below. Further work including the fat bloom examples have been published in a paper in the European Journal for Lipid Science Technology.2”


1.    P D Tran, (2017). Novel strategies to develop filled chocolates for the tropics - PhD thesis, Ghent University, Belgium, 258p.

2.    Controlling the stability of chocolates through the incorporation of soft and hard StOSt-rich fats; P D Tran et al, Eur. J. Lipid Sci. Technol. 2015, 117, 0000–0000, DOI: 10.1002/ejlt.201400584.

Quorum expands customer support and demonstration facilities in China

Quorum Technologies is pleased to announce the opening of a new demonstration laboratory at Nanjing Agricultural University, China, in association with distributors, Nanjing Tansi Technology Company.

Managing Director, Tony Larkin, was recently in Nanjing in China to open a new demonstration laboratory at Nanjing Agricultural University in association with distributor partners, the Nanjing Tansi Technology Company. Along with Commercial Director, Robert Hennig, Tony was present as Head of the Laboratory, Professor He, invited colleagues and potential new Chinese customers to see his electron microscope demonstrated with the Quorum PP3010T Cryo-SEM sample preparation system. 

The PP3010T is the latest generation of cryo-SEM technology and combines the highest quality results with unparalleled ease of use. It is a highly automated, column-mounted, gas-cooled cryo-SEM preparation and cryo-transfer system, which is suitable for most makes and models of W-SEM, FE-SEM and FIB/SEM. Professor He says “the PP3010T is very useful in our work. It helps to reveal images of biological samples in their real state.” 

Speaking about Tansi's investment in equipment, Tony said “I am delighted with the opportunity to work with Professor He and his team. They will be of tremendous assistance to our Chinese distributors. With access to our cryo-prep and coating systems in Professor He’s laboratory, Tansi are now able to show their customers the latest Quorum technologies. This follows on from similar commitments from our US partners, EMS, whose laboratory has one of the most comprehensive demonstration and training facilities outside of our own factory in Laughton. With more partners at facilities in Brno in the Czech Republic and UK universities including Nottingham and Leeds, we will continue to grow our support network as we seek to bring new advances through collaborations with our users worldwide.” 

The Physics Department of King’s College, London, uses the Quorum Q150T ES to gold coat samples for enhanced scanning electron microscopy imaging

With a wide range of samples to analyse and imaging requirements from the micron to the nanometre level, a reproducible and solid coating system was an essential requirement.

William (Bill) Luckhurst heads up the operation and maintenance of the instrumentation facilities of the Physics Department of King’s College, London. With nearly forty years’ experience, Bill has seen the development of many techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), thin film thermal evaporation and vacuum design & practice. These days, Bill and his colleague, Dr Ben Blackburn, are responsible for managing the use of the instrumentation, providing training and induction to new users. Bill also has many PhD students using the equipment as well as other University of London and private, industrial users. With high running costs, the laboratories have to be kept running 24/7 to earn their keep and to support the growing research activities such as the Physics Department Photonics research group.

Having modern, easy-to-use and reliable equipment are some of Bill’s criteria when he goes out to source new instrumentation. With a wide range of samples to analyse with imaging requirements from the micron to the nanometre level, a reproducible and solid coating system is essential. As Professor Al-Jamal Khuloud from the Pharmacy Department has said “coating our samples, submicron nanoparticles of a variety of shapes and dimensions, with thin layers of gold prior to SEM imaging not only enhances image contract, it conducts charge away from the surface.” Such requirements were important factors when Bill came to purchase a new coater around 18 months ago.

Bill takes up the story: “Procurement rules insist on three quotations and then a justification case for the purchase. When I requested a demonstration, Quorum were by far the most responsive of manufacturers. Other vendors were either not really interested or their products turned out to be prohibitively expensive. The QT150T ES was exactly what I needed at a price that I could afford in a package that looked good, was easy to use and maintain. The sample stages supplied with the instrument allow a diverse range of samples to be coated; the rotating planetary sample holder is particularly useful as it allows the even coating of irregular shaped samples. The user instruction and programming screen is a wheeze to use; tuition times for new users are around ten minutes and everyone is very happy. Additionally some researchers use the coater for other applications where they want a thin coherent film up to say 50 nm produced by a cold process where conventional thermal evaporation could damage a delicate surface.”

* Dr Ben Blackburn of the Physics Department, King’s College London, uses the Quorum Q150T ES coater to prepare samples for analysis by SEM.

Imperial College, London, uses the Quorum Q150T to deposit metals and ITO to make plasmonic sensors and electric contact pads

The Blackett Laboratory of the Physics Department at Imperial College chose the Q150T coater for a fast prototyping and development process.

Dr Avi Braun is a Research Associate in the Faculty of Natural Sciences, Department of Physics at Imperial College, London. Located in the Blackett Laboratory, Dr Braun joined the Quantum photovoltaic group in December 2013 as an Imperial College Junior Research Fellow. His main subject of research is the harnessing and integration of nano-photonic structures with photovoltaic and other opto-electronic and sensing applications. This research involves the design, simulation, fabrication and characterization of miniaturized opto-electronic devices and plasmonic sensors. 

Dr Braun uses the Quorum Technologies Q150T coater to deposit a variety of metals and ITO (indium-tin oxide) to make plasmonic sensors and electric contact pads. Describing what he particularly likes about the Q150T, Dr Braun says “In comparison with more sophisticated high vacuum systems, the Q150T is much faster thus allowing us to have a fast prototyping and development process. It is also very simple to use; this enables us to give students access to the system as part of their academic practical training. The metals we use include gold, silver, ITO and a nickel-copper alloy. These we deposit in a thickness range of 50-150 nm. We also put down adhesion layers of chromium and titanium to a thickness of 3-5 µm. We particularly like the way we are able to change targets – fast and simple. We also find the angled rotational stage very good for coating 3D structures.” 


Dr Braun and his colleague, Professor Stefan Maier, have published work in ACS SensorsIt describes the fabrication of plasmonic IR sensors using direct laser writing and metal deposition using the Q150T system. Entitled “Versatile direct laser writing lithography technique for surface enhanced infrared spectroscopy sensors”, the paper is available online through the American Chemical Society at ACS Sens.20161 (9), pp 1155–1162, DOI: 10.1021/acssensors.6b00469. 

Schematic from the abstract of the Braun & Maier paper published in ACS Sensors (referenced above). (Published here with the permission of the author, Dr Braun)

NMRC, University of Nottingham chooses the Quorum Q150 coater for its reliable and reproducible film thickness when coating samples with iridium.

Reliability and repeatability of metal film deposition thickness is important to the Nanoscale & Microscale Research Centre, which is why they have chosen to use a Q150T S coater in their facility.

Dr Elisabeth (Beth) Steer is Specimen Preparation Technician at the Nanoscale and Microscale Research Centre, (NMRC), in the Faculty of Science at the University of Nottingham. The Centre is a cross-faculty hub providing facilities and expertise for research across the engineering, physical and life sciences. The Centre is well placed and ready to support academics in achieving excellence in their research and leveraging the funding available in nanoscience and related interdisciplinary areas. It is proud host to a unique suite of over twenty instruments which facilitate the imaging and analytical investigation of materials from a wide range of scientific disciplines. The NMRC also welcomes commercial and industrial access making it one of the most versatile imaging centres in the country.

Beth’s work covers many different preparation processes. These include sputter coating, evaporation coating, critical point drying, resin embedding, microtomy & ultramicrotomy, polishing and grinding. The key to successful coating performance is reproducibility. Beth takes up the story: “We use the Quorum 150T S turbomolecular-pumped system to sputter coat samples with iridium here prior to analysis on a JEOL 7100 FEG-SEM. The iridium coating is essential as the other types of coating we have here (Pt, Au) have a grain size too large for use with the FEG as the structure of the coat covers nano features we’re trying to observe. When working on a nanoscale, it’s very important to have an even coat covering the samples that is reproducible. We tend to coat between 5-15 nm.”

Continuing, she says “Compared to our other coaters, the Q150T has a very controllable, easily reproducible coat – helped by the turbo pump. The reproducibility is very important to us as if we coat a sample with something that varies by a few nm then the sample is difficult to interpret and once we find a thickness that works for a sample type we need to be able to reproduce it to 1 nm. Film thickness is very important for us. It varies with every sample type, but we find the ability to produce coats <5 nm essential for FEG work and that isn’t really possible without a Film Thickness Monitor.”

Sales Manager, Dennis Fitzpatrick, says “Quorum offers the most versatile range of sputter and carbon coaters for electron microscopy today. The Q150T is available in three formats: sputtering, carbon evaporation or both. Depending upon the selected configuration, the Q150T can be a top-of-the-range sputter coater for high resolution scanning electron microscopy (SEM), a carbon coater suitable for SEM and transmission electron microscopy (TEM), or both - in a single easy-to-use system. Other options include metal evaporation and aperture cleaning.”

Carl Zeiss Microscopy has incorporated a Q150T coater into their rugged MinSCAN solution - designed for the mining, geosciences and oil & gas sectors.

The ZEISS mining and geosciences applications development group have chosen to use Quorum’s Q150T carbon & sputter coater to prepare mineral samples for analysis on their MinSCAN mineralogy laboratory system.

Shaun Graham is part of the applications development team at Carl Zeiss Microscopy based in Cambridge. With a Masters in applied and environmental geology, he works in the geosciences, mining and oil & gas sectors to provide analytical solutions using scanning electron microscopy performed on mineral samples. This includes the provision of sample preparation equipment including a turbo-pumped coater from Quorum Technologies

One of the main applications of the geosciences business, with its automated mineralogy software, is to provide data on mineral processing plant products from mining companies. It is vital that operating mines are able to track mineralogical and textural variation for processing and recovery optimizations. Recognising variability can save or make huge amounts of money to a company by maximizing yield and quality. The instrumentation has to be rugged and extremely reliable as it will often be located at the mine site itself. This has to be easy-to-use. Operators are not qualified scientists. They just require quick, accurate and actionable data to make informed decisions.

ZEISS supplies a special dedicated package to deliver to these requirements. This comprises sample preparation equipment and a “ruggedized” SEM. The system, known as MinSCAN, has been designed for this challenging environment, a mine-site mineralogy laboratory on wheels! A powerful data system takes the results to enable an increase in profits through greater concentrate quality and reduced losses to tailings (the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore.). Being able to rapidly troubleshoot recovery issues, optimize plant performance and complement assays gives metallurgists, mine managers and superintendents the confidence to make effective decisions based on reliable, quantitative data. 

Key to reproducible sample preparation is a Quorum Q150T providing high resolution carbon and sputter coating. Each 30 mm standard sample requires reproducible, uniform, thin coatings. Carbon coating is used in perhaps 80% of the applications where mineral particles are being investigated. For oil and gas applications, the ability of having a thin coating becomes most important when making porosity measurements. Uniform thinness will greatly reduce imaging artefacts. As Shaun says about the selection of Quorum coaters, “the Q150 series has been chosen based on its proven extremely reliable performance in what is usually a difficult environment far removed from the traditional research bench. The coater has to be available 24/7 as the failure to be able to coat a complete batch of daily samples in a day will risk loss of profit through the lack of actionable data from that days production. This is so important to our users that ZEISS supply, install and train users on all elements of the experimental process.” 

Technical Director, Bob Morrison, says “Quorum has a long established track record as the preferred supplier of coaters for mining applications. Reliability is extremely important in these situations and we have been able to demonstrate the reliability and performance of the Q150T coater in our dealing with partners like Zeiss over a number of years.” The Q150T is available in three formats: sputtering, carbon evaporation or both. Depending upon the selected configuration, the Q150T can be a top-of-the-range sputter coater for high resolution scanning electron microscopy (SEM), a carbon coater suitable for SEM and transmission electron microscopy (TEM), or both - in a single easy-to-use system. Other options include metal evaporation and aperture cleaning.

The Jensen Laboratory at the HHMI, Caltech, incorporates the Quorum Cryo-SEM preparation system in microbial cell biology with electron cryotomography

Alasdair McDowall is the EM Center Director in the Jensen Laboratory at the Howard Hughes Medical Institute located at Caltech. Headed by Professor Grant Jensen, the Lab uses Electron Cryotomography (ECT) to study the molecular architecture of microbial cells and HIV in their native state.

The focus is on the fundamentals of microbial cell biology such as cell division, movement and secretion, as well as the structure of HIV at all stages of its lifecycle. The lab opened its doors in 2002 and continues to push the boundaries of high resolution imaging today. However, the investigation of frozen hydrated whole cells (beam and vacuum sensitive materials) in the electron microscope chamber requires new solutions. The advances in techniques for the preparation of cells by Cryo Focused Ion Beam Milling for structural characterization have recently provided a new insight of these delicate cellular architectures.

Cryo Focused Ion Beam milling (cryo FIB milling) is a cutting-edge method for thinning vitrified biological samples that allows access to intracellular regions of thick specimens (> 1 um) with unprecedented ease and structural preservation. It provides the ability to move beyond imaging only small bacterial cells with electron cryotomography (ECT) and will allow the exploration of eukaryotic cells, tissues and microbial biofilms to the same molecular resolution that the group has achieved with individual bacterial cells for the past decade. In addition, the ability to thin individual bacterial cells before imaging, without perturbing their structure, will provide higher contrast and resolution when necessary, even within already thin bacterial cells. Furthermore, the addition of a cryo-stage to the existing FIB mill at Caltech will allow for further development of much needed methods for correlating fluorescence microscopy and electron tomography for the targeting and identification of specific structures deep within eukaryotic cells, bacteria and tissues.

Dr McDowall uses the Quorum PP3010T cryo sample preparation system. This is a highly automated, easy-to-use, column-mounted, gas-cooled Cryo-SEM preparation system suitable for most makes and models of SEM, FE-SEM and FIB/SEM. The Jensen group uses their prep system with an FEI Versa scanning electron microscope. Dr McDowall says “The Quorum PP3010T is ideal for our vitreous cell transfers when dedicated to maintaining the cryogenic amorphous state during SEM and DualBeam specimen preparation. The PP3010T allows easier and more practical operation for milling cryo preserved specimens for electron tomography. Its design assists the investigation of frozen hydrated cells and tissues by providing a mechanism for hydrated sample transfer, cryogenic cooling and temperature control within the SEM or Small Dual Beam during the milling process. In our operation, the Quorum PP3010T was added to an existing FEI Versa Dual Beam Scanning Electron Microscope in a climate controlled room courtesy of the Greer group, California Institute of Technology.”

Experienced electron microscopist, David McCarthy, talks about working with Quorum and his use of their coaters and cryo-SEM preparation instrumentation.

David McCarthy has been working in the world of electron microscopy since the early 70s. In this time, he has seen many changes in instrumentation, techniques and sample preparation methods.

His career started back at the London Hospital Medical School for four and a half years before a move that would see him start and manage the Electron Microscopy Unit at the School of Pharmacy, University College London for thirty eight years. In this time, he has used a number of EMs starting with Philips and JEOL systems. In 1991 he was able to purchase the first fully digital SEM in the UK, a Philips XL20. Then on to larger chamber XL30 and in 2009 he ended up with the FEI Quanta 200 FEG. This gave him a versatile, high resolution low-vacuum FEG SEM to handle really challenging thermally and vacuum sensitive samples and dynamic experiments. In parallel with the microscopes came new and more advanced accessories enabling advanced cryo-imaging. At all times, a high performance vacuum coating system was essential to McCarthy’s work.

McCarthy has worked with Quorum over many years. For example, while running the EM Unit at UCL, he acquired a PP3010T cryo-SEM preparation system, a highly automated, column-mounted, gas-cooled sample preparation and transfer system. He also used their Q150T series of sputter and carbon coaters, something he has continued to this day with his contract service business based out in rural Suffolk. DM Microscopy offers McCarthy’s extensive experience in electron microscopy to a range of academic and industrial pharmaceutical organisations. His new laboratory uses a Tescan Vega 3 SEM, a reliable high vacuum, turbo-pumped tungsten system. It is used to enable DM Microscopy to provide rapid turnaround imaging services, vital in the world of pharma. His sample coater started life as a Q150 E compact rotary-pumped unit for evaporation applications using carbon coating of specimens. Quorum has recently upgraded the unit to a Q150R ES to provide gold sputtering of samples. McCarthy is particularly impressed with his dealings with Quorum. “They provide excellent service and support on the back of a very versatile coating system. I chose the option of the quartz oscillator film thickness monitor (FTM) as this enables me to lay down very accurate amounts of material, to ensure reproducible sample preparation conditions prior to imaging. Operation is very straightforward via a touch screen. This enables me to store my protocols for ease of setting up and running.”