by Dr.-Ing. Katja Tonisch, Technische Universität Ilmenau
07.11.2019, 17:00 h, TF, Aquarium
to be announced
by Prof. Dr. Galina Kurlyandskaya, University of the Basque Country UPV-EHU
24.10.2019, 16:00 h, TF, Aquarium
to be announced
by Prof. Dr. Hiroshi Onishi, Kobe University, Japan
10.09.2019, 09:00 h, Physics Department, Leibnizstr. 19, 24118 Kiel, Room 614
Frequency-modulation atomic force microscopy (FM-AFM) is a promising tool to observe solid topography and also liquid structure at liquid-solid interfaces. The cantilever with a tip is mechanically oscillated. The shift of the resonance frequency, delta-f, represents the force pushing or pulling the tip. Microscopes with a force sensitivity of 10 pN or better in water and organic solvents have been developed and commercialized to date. Using the advanced microscopes, we have examined structured liquids at a number of interfaces including water-CaCO3, Al2O3, SrTiO3, hydrophilic molecular monolayers, organic compounds. The observed delta-f distributions are interpreted with water density distribution through Gibbs free energy perturbed by the solid surface. The force sensitivity of 10 pN is the key for probing force on single liquid molecules. Possible application of Δf mapping to tribology research will also be mentioned.
by Prof. Dr. Paulo Freitas, International Iberian Nanotechnology Laboratory, Braga, Portugal
14.02.2019, 17:00 h, TF, Seminar room C-SR 1
Spintronic sensors are being used for a variety of applications from read heads in hard disks and memory elements in MRAM cells, to current, position (linear and angular), and magnetic field sensors used in automotive, a variety of industrial, and more recently in biomedical/biosensor applications1,2,3. These magnetoresistive sensors can be integrated over CMOS in a back end process (MRAM and monolithic sensors). For most applications, S/N at the relevant frequency of operation (from DC to GHz), thermal stability ( of the various magnetic layers in the stack), voltage output, determine the type of sensor to be used. Typical GMR/TMR individual sensors with micron size features reach detectivities down to few nT at low frequencies (10Hz). When connected in arrays, S/N can be improved by SQR N. Soft flux guides can also be used (gain up to few hundred). With these architectures detectivities down to 10 -100pT at 10Hz can be reached. These sensors can also be fabricated in flexible polyimide substrates if required keeping standard characteristics, as well as be integrated in MEMS structures as cantilevers and microneedes. Examples of applications in the biomedical area will be given (protein or DNA integrated biochip platforms, integrated cytometers use for cell/bacteria separation and enumeration, magnetrodes used for neural magnetic field recording).
1 “Spintronic Sensors”, P.P.Freitas, R.Ferreira and S.Cardoso, Proceedings of the IEEE, 104 (10), pp. 1894 - 1918 (2016); 10.1109/JPROC.2016.2578303
2 “Challenges and trends in magnetic sensor integration with microfluidics for biomedical applications”,S.Cardoso, D.Leitao, T.Dias, J.Valadeiro, M.Silva, A.Chicharo, V.Silverio, J.Gaspar and P.P.Freitas, Journal of Physics D-Applied Physics, 50 (21), 213001 (2017); https://doi.org/10.1088/1361-6463/aa66ec
3 “Lab-on-Chip Devices: Gaining Ground Losing Size”, V.C. Romao, S. A. M. Martins, J.Germano, F. A.Cardoso, S.Cardoso, P.P. Freitas, ACS Nano 11 (11), pp 10659–10664 (2017); DOI: 10.1021/acsnano.7b06703
by Prof. Dr. Dave C. Johnson, University of Oregon
05.02.2019, 16:00 h, TF, Aquarium
By controlling the composition of an amorphous intermediate on the nanoscale it is possible to kinetically control the self-assembly of new nanostructured compounds consisting of two or more compounds with different crystal structures that are precisely interleaved on the nanoscale. We have used this approach to synthesize hundreds of new metastable compounds with designed nanostructure, including structural isomers. Many of these materials have unprecedented physical properties, including the lowest thermal conductivities ever reported for a fully dense solid, systematic structural changes dependent on nanostructure, and charge density wave transitions. The ability to prepare entire families of new nanostructured compounds and equilibrating them to control carrier concentrations permits a new "thin film metallurgy" or “nanochemistry” in which nanostructure and composition can both be used to tailor physical properties, interfacial structures can be determined for precisely defined constituent thicknesses, and interfacial phenomena and modulation doping can be systematically exploited.
by Prof. Dr. Leonhard M. Reindl, Albert-Ludwigs-Universität Freiburg
04.02.2019, 17:15 h, TF, Aquarium
Wireless sensor or actuator systems, like portable phones, remote control, ID cards, or embedded wireless sensor nodes play an ever growing role in our industrialized environment. Those systems were enabled due to the steadily decreasing power consumption of high integrated ICs. Most such systems are powered by batteries or inductive coupling. In this presentation several concepts for an alternative power supply of wireless sensor or actuator systems are discussed in detail.
Batteries, although today mostly used, suffer from a limited storage capacity, which induce a labor and sometimes cost-intensive periodic maintenance, and also a problematic ecological impact. The usable range for inductive coupling systems is restricted to a distance of about the aperture of the coupling coil. UHF systems operate in the far field and reach higher distances. Their operating range is limited by the distance where the voltage at the feeding point of the antenna becomes too low to drive the rectifier circuit. Larger read out ranges become feasible by omitting the rectifier stage. In this case we need either a passive frequency modulating device to shift the read out signal to a side band, or a resonator with a high quality factor, like a SAW, BAW, or a dielectric resonator, to store the energy until all environmental echoes are fade away. For many applications, both indoor and outdoor, energy harvesting system become feasible which convert ambient power densities like light, RF fields, local or temporal thermal gradients, or mechanical vibrations into electrical supply power for the wireless system.
All those systems strongly suffer from a lack of energy. Thus new concepts for lowering the power consumption of a wireless sensor or actuator system - by keeping their performance - remain extreme important. Hereby, a wireless wake up receiver technique is presented which operates on a current requirement as low as 3 micro A.
Several application examples of the presented systems will be given, e.g., sensors for industry 4.0, indoor position sensors, inductively transmitted power to implants, and high temperature wireless sensors.