Precise positioning: microscope stages with cobalt-samarium coated metal bands

Dr. Bandorf, you are researching hard magnetic coatings for high-precision microscopy. What is the inspiration behind the project?

Ralf Bandorf: We were looking for a vacuum coating technology that is suitable for magnetic thin-film deposition. The problem with traditional vacuum coating is that it often uses a magnetic field for layer deposition but is short-circuited by magnetic materials. This results in a relatively low deposition rate in cases with magnetic materials. We have teamed up with the Technical University of Braunschweig and have been collaborating on this subject for several years. Our first testing of various magnetic materials dates back to 2005. In 2013/2014, ITK Dr. Kassen approached us since the company uses magnetic positioning systems versus optical positioning systems for microscope stages. This prompted us at the Fraunhofer IST to develop hard magnetic cobalt-samarium coatings for magnetic linear scales. We make coating strips that are embedded in the microscope tables. Combined with sensors and a special algorithm, these linear scales enhance the positioning accuracy of the microscope stage. Biological material such as cells can move, which is why you need to be able to steer to the right position with micrometer accuracy.

How do these strips work in the microscope stages?

Bandorf: We first apply a cobalt-samarium coating to non-magnetic metal strips. This gives the strips a defined magnetic structure that can be encoded with a signal pattern or structure that can be read by a read head. Videotapes work in a similar way, for example. This functional coding characterizes an absolute scale and determines the precise position of the strip on the microscope stage. The coatings enable a position resolution of 5 nanometers.

Can the coated strips be retrofitted for other products or is this a special application for just one company?

Bandorf: The strips can basically also be used for other applications. At the end of the day, it is a metal strip with a magnetic coating that you can write on and apply as you see fit. We test and analyze other applications in close collaboration with our industry partner ITK Dr. Kassen and plan to bring them to market.

The press release underscored that the strips are highly sustainable. How so?

Bandorf: This is a plate made of a magnetic material and pure argon gas and no other waste materials. Unlike other processes, this method does not involve the use of toxic substances, making it more eco-friendly. The overall system is also unaffected by interference fields.

You conduct research in a laboratory setting, which means you can presumably only make small quantities of the magnetic strips. What about industrial-scale production? What is your cost estimation in this case?

Bandorf: As a Fraunhofer Institute, our primary emphasis is on applied research. Apart from laboratory and test facilities, we also have industrial equipment, allowing us to scale and support the growth of our technology. We are currently making small pieces, measuring only a few meters. However, it is possible to wind the magnetic strips onto rolls. We already have some feasible approaches and solutions to support this point. Here is the basic principle: You need a certain material thickness to produce a signal via the magnetic strip. We use cobalt-samarium, which is not exactly the cheapest material. When it comes to industrial applications, you must perform a cost-benefit analysis and consider suitable applications carefully. Needless to say, we team up with our partners and continue exploring alternative, more cost-effective materials. So far, those materials have not yet resulted in the accuracy and precision we are aiming for. This requires an in-depth understanding of the correlation between material properties and process parameters. The process we developed is already suitable for series and industrial production and high-volume manufacturing.