ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT wigner.mta.hu>]

*WIGNER SZFI Seminar*
Combining magnetic forces for contactless manipulation of fluids in
microelectrode-microfluidic systems

*Margitta Uhlemann *
IFW Dresden, Germany (host: Péter László)

Thursday, 27 June 2019 10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference
Room

New technologies based on transport, mixing, actuation and manipulation of
fluids and objects in the micro- and nanometer scale are rapidly
developing. The enormous scientific and technological interest focuses on
total microanalysis approaches which are applicable in analytics and
monitoring in medicine, biology, and the environment. Contactless external
driving forces such as electric or magnetic fields and field gradients for
tailored fluid manipulation and electrochemical and analytical approaches
are of increasing interest. Several microfluidic systems were employed to
demonstrate the concept of fluid manipulation by overlaying
magnetohydrodynamic (MHD) effects generated by the Lorentz force and the
magnetic field gradient force [1]. Combining these two forces a novel
method to drive and manipulate fluid in a contactless way in a
microelectrode-microfluidic system is demonstrated. The method is based on
the redox-reaction [Fe(CN)6]3-/[Fe(CN)6]4- performed in a magnetic field
oriented perpendicular to the ionic current generating a
magnetohydrodynamic flow [2]. Additionally a moveable magnetized CoFe
micro-strip is placed beneath a selected electrode. In this region, the
magnetic flux density is changed locally and a strong magnetic field
gradient is formed. The redox-reaction changes the magnetic susceptibility
of the electrolyte near the electrodes, and the resulting field gradient
force exerts a force on the fluid which leads to a deflection of the main
flow that is primarily driven by the Lorentz force. Particle image velocity
measurements and numerical simulations demonstrate that by combining the
two magnetic forces, the flow is not only redirected, but also a local
change of concentration of paramagnetic species is realized demonstrated in
Figure 1 [3]. It is expected that this unique method will provide a
promising tool for a wide range of analytical and biological applications
[4].

[1]: M. Uhlemann, K. Tschulik, A. Gebert, et al., Eur. Phys. J. Special
Topics 220, 287–302 (2013)
[2] M. C. Weston, Ch. K. Nash, J.J. Homesley, I. Fritsch, Anal. Chem. 84,
9402-9409 (2012)
[3] X.Yang, K. Tschulik, M. Uhlemann, St. Odenbach, K. Eckert, J. Phys.
Chem. Lett. 3, 3559 (2013)
[4] V. Hähnel, F. Z. Khan, G. Mutschke, Ch. Cierpka, M. Uhlemann, I.
Fritsch, submitted to Sci. Rep.

Everyone is welcome to attend.

János Asbóth
szfi-seminar AT wigner.mta.hu