{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T18:45:43Z","timestamp":1779907543501,"version":"3.53.1"},"reference-count":30,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2019,6,7]],"date-time":"2019-06-07T00:00:00Z","timestamp":1559865600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002347","name":"Bundesministerium f\u00fcr Bildung und Forschung","doi-asserted-by":"publisher","award":["13N13712"],"award-info":[{"award-number":["13N13712"]}],"id":[{"id":"10.13039\/501100002347","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In modern bioanalytical methods, it is often desired to detect several targets in one sample within one measurement. Immunological methods including those that use superparamagnetic beads are an important group of techniques for these applications. The goal of this work is to investigate the feasibility of simultaneously detecting different superparamagnetic beads acting as markers using the magnetic frequency mixing technique. The frequency of the magnetic excitation field is scanned while the lower driving frequency is kept constant. Due to the particles\u2019 nonlinear magnetization, mixing frequencies are generated. To record their amplitude and phase information, a direct digitization of the pickup-coil\u2019s signal with subsequent Fast Fourier Transformation is performed. By synchronizing both magnetic fields, a stable phase information is gained. In this research, it is shown that the amplitude of the dominant mixing component is proportional to the amount of superparamagnetic beads inside a sample. Additionally, it is shown that the phase does not show this behaviour. Excitation frequency scans of different bead types were performed, showing different phases, without correlation to their diverse amplitudes. Two commercially available beads were selected and a determination of their amount in a mixture is performed as a demonstration for multiplex measurements.<\/jats:p>","DOI":"10.3390\/s19112599","type":"journal-article","created":{"date-parts":[[2019,6,7]],"date-time":"2019-06-07T11:35:05Z","timestamp":1559907305000},"page":"2599","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["Multiplex Detection of Different Magnetic Beads Using Frequency Scanning in Magnetic Frequency Mixing Technique"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0666-912X","authenticated-orcid":false,"given":"Stefan","family":"Achtsnicht","sequence":"first","affiliation":[{"name":"Institute of Complex Systems Bioelectronics (ICS-8), Forschungszentrum J\u00fclich, 52425 J\u00fclich, Germany"},{"name":"RWTH Aachen University, 52062 Aachen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6904-1447","authenticated-orcid":false,"given":"Ali Mohammad","family":"Pourshahidi","sequence":"additional","affiliation":[{"name":"Institute of Complex Systems Bioelectronics (ICS-8), Forschungszentrum J\u00fclich, 52425 J\u00fclich, Germany"},{"name":"RWTH Aachen University, 52062 Aachen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6143-2702","authenticated-orcid":false,"given":"Andreas","family":"Offenh\u00e4usser","sequence":"additional","affiliation":[{"name":"Institute of Complex Systems Bioelectronics (ICS-8), Forschungszentrum J\u00fclich, 52425 J\u00fclich, Germany"},{"name":"RWTH Aachen University, 52062 Aachen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7526-9894","authenticated-orcid":false,"given":"Hans-Joachim","family":"Krause","sequence":"additional","affiliation":[{"name":"Institute of Complex Systems Bioelectronics (ICS-8), Forschungszentrum J\u00fclich, 52425 J\u00fclich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,6,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"R167","DOI":"10.1088\/0022-3727\/36\/13\/201","article-title":"Applications of magnetic nanoparticles in biomedicine","volume":"36","author":"Pankhurst","year":"2003","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Chen, Y.-T., Kolhatkar, A.G., Zenasni, O., Xu, S., and Lee, T.R. (2017). Biosensing using magnetic particle detection techniques. Sensors, 17.","DOI":"10.3390\/s17102300"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1894","DOI":"10.1021\/acssensors.8b00420","article-title":"Detecting biothreat agents: From current diagnostics to developing sensor technologies","volume":"3","author":"Walper","year":"2018","journal-title":"ACS Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1016\/S0956-5663(00)00108-1","article-title":"A review of molecular recognition technologies for detection of biological threat agents","volume":"15","author":"Iqbal","year":"2000","journal-title":"Biosens. Bioelectron."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1178","DOI":"10.1016\/j.bios.2010.07.033","article-title":"Recent advances in recognition elements of food and environmental biosensors: A review","volume":"26","author":"Dorst","year":"2010","journal-title":"Biosens. Bioelectron."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"4199","DOI":"10.1063\/1.1483909","article-title":"Detection of a single magnetic microbead using a miniaturized silicon hall sensor","volume":"80","author":"Besse","year":"2002","journal-title":"Appl. Phys. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.bios.2016.04.046","article-title":"Portable, one-step and rapid GMR biosensor platform with smartphone interface","volume":"85","author":"Choi","year":"2016","journal-title":"Biosens. Bioelectron."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"074903","DOI":"10.1063\/1.3340861","article-title":"Immunomagnetic reduction assay using high-tc superconducting-quantum-interference-device-based magnetosusceptometry","volume":"107","author":"Chieh","year":"2010","journal-title":"J. Appl. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3678","DOI":"10.1109\/77.622216","article-title":"Squid based remanence measurements for immunoassays","volume":"7","author":"Matz","year":"1997","journal-title":"IEEE Trans. Appl. Supercond."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"945","DOI":"10.1016\/j.bios.2003.09.005","article-title":"Biomolecular reactions studied using changes in brownian rotation dynamics of magnetic particles","volume":"19","author":"Astalan","year":"2004","journal-title":"Biosens. Bioelectron."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"869","DOI":"10.1038\/nm.1711","article-title":"Chip\u2013nmr biosensor for detection and molecular analysis of cells","volume":"14","author":"Lee","year":"2008","journal-title":"Nat. Med."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"436","DOI":"10.1016\/j.jmmm.2006.10.1164","article-title":"Magnetic particle detection by frequency mixing for immunoassay applications","volume":"311","author":"Krause","year":"2007","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"212512","DOI":"10.1063\/1.2206557","article-title":"Magnetic susceptibility reduction method for magnetically labeled immunoassay","volume":"88","author":"Hong","year":"2006","journal-title":"Appl. Phys. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1016\/j.jmmm.2006.10.1175","article-title":"Francisella tularensis detection using magnetic labels and a magnetic biosensor based on frequency mixing","volume":"311","author":"Meyer","year":"2007","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"973","DOI":"10.1016\/j.bios.2006.04.001","article-title":"CRP determination based on a novel magnetic biosensor","volume":"22","author":"Meyer","year":"2007","journal-title":"Biosens. Bioelectron."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"3039","DOI":"10.1128\/AEM.03667-14","article-title":"Simple and portable magnetic immunoassay for rapid detection and sensitive quantification of plant viruses","volume":"81","author":"Rettcher","year":"2015","journal-title":"Appl. Environ. Microbiol."},{"key":"ref_17","unstructured":"Vashist, S.K., and Luong, J.H.T. (2018). Chapter 1\u2014Immunoassays: An overview. Handbook of Immunoassay Technologies, Academic Press."},{"key":"ref_18","unstructured":"Vashist, S.K., and Luong, J.H.T. (2018). Chapter 17\u2014Immunoassays: Future prospects and possibilities. Handbook of Immunoassay Technologies, Academic Press."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1639","DOI":"10.1016\/j.jmmm.2009.02.104","article-title":"Multiparametric magnetic immunoassays utilizing non-linear signatures of magnetic labels","volume":"321","author":"Lenglet","year":"2009","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Achtsnicht, S., T\u00f6dter, J., Niehues, J., Tel\u00f6ken, M., Offenh\u00e4usser, A., Krause, H.-J., and Schr\u00f6per, F. (2019). 3D printed modular immunofiltration columns for frequency mixing-based multiplex magnetic immunodetection. Sensors, 19.","DOI":"10.3390\/s19010148"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/LMAG.2017.2754238","article-title":"Harmonic simulation study of simultaneous nanoparticle size and viscosity differentiation","volume":"8","author":"Shasha","year":"2017","journal-title":"IEEE Magn. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3139","DOI":"10.1088\/1361-6560\/aa5e90","article-title":"Multi-color magnetic nanoparticle imaging using magnetorelaxometry","volume":"62","author":"Coene","year":"2017","journal-title":"Phys. Med. Biol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"173701","DOI":"10.1063\/1.4934743","article-title":"A simulation study on superparamagnetic nanoparticle based multi-tracer tracking","volume":"107","author":"Wu","year":"2015","journal-title":"Appl. Phys. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.jmmm.2014.10.034","article-title":"Colorize magnetic nanoparticles using a search coil based testing method","volume":"380","author":"Wu","year":"2015","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"140","DOI":"10.1016\/j.jmmm.2014.08.050","article-title":"Resolving particle size modality in bi-modal iron oxide nanoparticle suspensions","volume":"380","author":"Lak","year":"2015","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_26","first-page":"24","article-title":"Characterization of magnetic particles and microspheres and their magnetophoretic mobility using a digital microscopy method","volume":"3","author":"Ciocan","year":"2002","journal-title":"Eur. Cells Mater."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"585","DOI":"10.1002\/cyto.a.22866","article-title":"Magnetic particle characterization\u2014Magnetophoretic mobility and particle size","volume":"89","author":"Zhou","year":"2016","journal-title":"Cytom. Part A"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"244","DOI":"10.1016\/j.jmmm.2018.10.066","article-title":"Measurement of the magnetophoretic velocity of different superparamagnetic beads","volume":"477","author":"Achtsnicht","year":"2019","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"073012","DOI":"10.1088\/1367-2630\/aa73b4","article-title":"Distribution functions of magnetic nanoparticles determined by a numerical inversion method","volume":"19","author":"Bender","year":"2017","journal-title":"New J. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.jmmm.2016.11.113","article-title":"Size analysis of single-core magnetic nanoparticles","volume":"427","author":"Ludwig","year":"2017","journal-title":"J. Magn. Magn. Mater."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/11\/2599\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:56:55Z","timestamp":1760187415000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/11\/2599"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,6,7]]},"references-count":30,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2019,6]]}},"alternative-id":["s19112599"],"URL":"https:\/\/doi.org\/10.3390\/s19112599","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,6,7]]}}}