Making the invisible visible – The SNI’s Nano Imaging Lab unlocks the secrets of the nanoworld

 In early 2016, the SNI welcomed four new members. Evi Bieler, Susanne Erpel, Daniel Mathys and group leader Dr. Markus Dürrenberger of the former Center for Microscopy Basel (ZMB) joined Dr. Monica Schönenberger, previously of the Nanotech Service Lab, to form the new Nano Imaging Lab (NI Lab). The five specialists bring together decades of experience in imaging minute structures. Drawing on their unique expertise and extensive technical resources, they offer a comprehensive imaging service to clients in the SNI Network and external partners alike.

A varied toolkit
The stunningly detailed images captured by electron microscopes never fail to catch the eye. However, the work of the five members of the Nano Imaging Lab is about more than simply showcasing the beauty of the nanoworld. Their microscopic images help researchers examine structures, analyze particles and solve problems. Depending on the nature of the sample and the client’s needs, the NI Lab has a range of microscopes at its disposal.

For instance, the team uses scanning electron microscopes (SEM) to examine how different bone replacement materials are colonized by cells. The project, led by Professor Ivan Martin of University Hospital Basel, has a twofold aim: to assess how well body cells respond to implants, and to determine how certain materials affect unwanted bacterial growth. The detailed images provided by the NI Lab help the researchers choose the most appropriate surface structures and materials.

Keeping it cool
While the researchers working on bone replacement materials want to see as few bacteria as possible, in other projects these tiny single-celled organisms are the primary focus. Delicate microorganisms are best viewed using a cold-field-emission SEM, a low-energy device which is particularly gentle on the sample. Examples of research issues where this procedure is particularly useful include the way in which bacteria are attacked and infected by viruses, or how bacteria attach themselves to surfaces and other bacteria by means of thread-like appendages known as pili.

Fragile mirrors
The applications of the cold-field-emission microscope are not limited to delicate organic structures: the NI Lab team also uses the device to examine special mirrors for use in the planned ITER fusion reactor. The team working on the project, led by Dr. Laurent Marot of the University of Basel’s Department of Physics, has developed a method for cleaning the light-reflecting mirror surfaces inside the reactor. These extremely sensitive mirrors must be examined at very high resolution while avoiding radiation damage, making the cold-field-emission microscope an obvious choice.

Possibility of nanofabrication

The NI Lab also has a scanning electron microscope equipped with a focused ion beam (FIB), which can be used to manipulate minute structures. The FIB has been used to cut solar cell wafers and examine their layer structure in collaboration with Professor Edwin Constable of the Department of Chemistry, for example. For a project led by Professors Christoph Gerber (Department of Physics) and Daniel Müller (D-BSSE), special silicon cantilevers were produced in a painstaking process lasting hours. These cantilevers enable the researchers to examine the mechanics of cell division. They discovered that the cell division of human cells can be controlled using these cantilevers.

Examining pests

For other research issues involving organic matter, the NI Lab team uses a scanning electron microscope with the ability to plunge-freeze samples. An examination temperature of -150°C makes it possible to obtain largely artifact-free specimens from organic materials. The process, known as cryo-SEM, is currently being used in a project involving the State Viticultural Institute in Freiburg (Germany) to find out how the micro- and nanostructure of different vine varieties affects the susceptibility of leaves and grapes to pests.

More than just images
However, images are not the only way in which SEMs can help solve research problems, however. Spectroscopic analysis can also be used to obtain a qualitative and quantitative description of most of the elements contained in the material being examined. In a project for the company Particle Vision GmbH, for instance, the NI Lab analyzed air samples on newly developed boron substrates to support the analysis and services provided by Particle Vision.

The lab also investigates a wide range of nanoparticles. Using a transmission electron microscope, which allows researchers to image a sample’s internal structure, a group led by Professor Wolfgang Meier of the Department of Chemistry is exploring the possibilities offered by nanocontainers. The focus of the research is on the size distribution of the vesicles, which can be filled with a variety of substances, as well as the contents themselves.

AFM also among the lab’s resources
At the start of 2016, the former Nanotech Service Lab, led by Monica Schönenberger, became a part of the NI Lab, where Monica Schönenberger continues to offer a wide range of analyses using atomic force microscopy. She is currently working on the Argovia project NanoSilkTex, researching the surfaces of synthetic fibers treated with silk proteins.

A wealth of experience at the service of clients
A complete description of the services offered by the Nano Imaging Lab’s accomplished team is beyond the scope of this brief outline. Clients interested in a specific analysis will be competently advised by any of the NI Lab’s five members. Where desired, the team can take charge of the entire process, from sample preparation to documentation. However, certain customers, such as colleagues in the fields of environmental sciences or geology, prefer to conduct the analyses themselves using the NI Lab’s equipment. These clients also receive full professional support from the lab’s experienced team. Besides providing tailored services to clients, the NI Lab is also involved in teaching and in the outreach activities of the Biozentrum and SNI. For years, students at the Biozentrum or enrolled in the nanoscience study program have been praising the block courses offered by the NI Lab as a highlight of their studies, while visitors to the university’s open events are invariably fascinated by its extraordinary images of the nano- and microworlds.