The DynoMag system
The DynoMag system is a portable AC susceptometer for measuring the dynamic magnetic properties of liquids, powders, and solids. The frequency range is from 1 Hz up to 500 kHz with a resolution in magnetic moment better than 10-11 Am2 at 1 kHz. The induction technique is used to detect the AC susceptibility. The magnetic flux change due to the sample is detected with a well-balanced detection-coil system. The detection-coil system is centered around an excitation coil system connected to an AC-source that delivers the time-dependent current to the excitation coil that gives the excitation field. The signals from the detection coil system are fed into a low-noise lock-In amplifier. The DynoMag calibration procedure is one of the key features and ensures the large frequency range and high resolution in magnetic moment.
The system software governs the entire experimental set up (such as the time constant setting, the lower and upper field range, and the number of data points) and the collection of the data and presentation of the result in a user-friendly interface. For the detection of magnetic particles comprising single-domain crystals with slow internal relaxations, it can also determine the size distribution of
the particles.
Dynamic magnetic characterization
AC susceptometry has a vast area of application from magnetic-particle manufacturing to measuring soils in geophysical applications. For detecting the Brownian relaxation of particles, including thermally blocked single domains, we are able, from empirical data, to determine the size distribution of the particles using an algorithm included in the software of the dynamic susceptibility system. With the same instrument, we can also study the clustering of the particles and follow the binding reactions of different substances to the surface of the particles. At Imego, we are using this method in a biosensor system in which we detect the concentration of different kinds of biomolecules in a liquid.
Selected reference publications
- Teresa Zardán Gómez de la Torre, David Herthnek, Anja Mezger, Christer Johansson, Peter Svedlindh, Mats Nilsson, Maria Strømme, Detection of Rolling Circle Amplified DNA Molecules using Probe Tagged Magnetic Nanobeads in a portable AC susceptometer, Biosensors and Bioelectronics 29 (2011) 195 – 199.
- Fredrik Ahrentorp, Andrea P. Astalan, Christian Jonasson, Jakob Blomgren, Bin Qi, Olin Thompson Mefford, Minhao Yan, Jérémie Courtois, Jean-François Berret, Jérôme Fresnais, Olivier Sandre, Silvio Dutz, Robert Müller and Christer Johansson, Sensitive High Frequency AC Suceptometry in Magnetic Nanoparticle Applications, AIP Conference Proceedings, Volume 1311, pp. 213-223 (2010).
- Frederik W. Østerberg. Bjarke T. Dalslet, Detlef Snakenborg, Christer Johansson and Mikkel F. Hansen, Chip-Based Measurements of Brownian Relaxation of Magnetic Beads Using a Planar Hall Effect Magnetic Field Sensor, AIP Conference Proceedings, Volume 1311, pp. 176-183 (2010).
- D. Eberbeck, A.P. Astalan, K. Petersson, F. Wiekhorst, C. Bergemann, C. Johansson, U. Steinhoff, H. Richter, A. Krozer, L. Trahms, AC susceptometry and magnetorelaxometry for magnetic nanoparticle based biomolecule detection, in: J. Vander Sloten, P. Verdonck, M. Nyssen, J. Haueisen (Eds.): ECIFMBE 2008, IFMBE Proceedings 22, pp. 2317–2321, 2008, Springer-Verlag Berlin Heidelberg 2009.
- Andrea Fornara, Petter Johansson, Karolina Petersson, Stefan Gustafsson, Jian Qin, Eva Olsson, Dag Ilver, Anatol Krozer, Mamoun Muhammed and Christer Johansson, Tailored Magnetic Nanoparticles for Direct and Sensitive Detection of Biomolecules in Biological Samples, Nano Letters, 2008, 8 (10), pp 3423–3428.
- Andrea Prieto Astalan, Jakob Blomgren, Karolina Petersson, Christian Jonasson, Dag Ilver, Christer Johansson and Anatol Krozer, Brownian relaxation measurement in the time domain of thermally blocked magnetic nanoparticles, Proceedings of Eurosensor XX in Gothenburg, 2006.
- Andrea Prieto Astalan, Christian Jonasson, Karolina, Petersson, Jakob Blomgren, Dag Ilver, Anatol Krozer and Christer Johansson, Magnetic response of thermally blocked nanoparticles in a pulsed magnetic field, J. Magn. Magn. Mat. 311 (2007) 166-170.