Session: 01-09: Magnetic Materials

Paper Number: 110998

110998 - Characterization of Wetting Properties of Magnetoactive Elastomer Surfaces 

Magneto-responsive surfaces have recently attracted attention of researchers because they provide a remote, non-destructive, and real-time (dynamic) approach for controllable manipulation of non-magnetic liquids. Prospective technological applications range from droplet-based microfluidics, microreactors, and liquid distributors, to fog harvesting, etc. A promising material system for realization of these smart surfaces are magnetoactive elastomers (MAEs) comprising micrometer-sized ferromagnetic particles embedded in a mechanically soft polymer matrix. Since the wetting properties are crucial for manipulation of liquids, MAE surfaces must be characterized correspondingly.

Commercially available contact angle (CA) measuring devices usually do not allow for the application of magnetic fields to the sample under test. We report a custom-built setup for measuring the CA of liquids on magneto-responsive surfaces. The addition of a programmable linear stage, which moves a permanent magnet, allows for the fine control of magnetic field applied to the MAE without the need for large and power consuming electromagnets.  Paired with a custom control and evaluation software, this measurement setup operates in a semiautomatic fashion, limiting operator error and increasing precision, speed, and repeatability of static and dynamic CA measurements for different magnetoactive materials. The software is equipped with robust droplet fitting algorithms that can suitably manage experimental challenges arising with soft magnetoactive materials, such as curling of sample edges or diffuse non-reflective surfaces. The algorithms for fitting the droplet contours are analyzed with regard to their robustness and precision.

Investigated MAE materials employ carbonyl iron particles as a filler and specifically synthesized soft polydimethylsiloxane (PDMS) matrices. Several application examples involving water droplets on flat and microstructured [1] MAE surfaces are presented for different MAE compositions. The measurements include static and dynamic (advancing and receding) contact angles at different flow rates. Obtained results show a significant dependence of wetting properties on the applied magnetic field. In particular, a clearly pronounced hysteresis of contact angles with regard to the magnetic field is observed.

References

[1]  G. Kravanja, I. A. Belyaeva, L. Hribar, I. Drevenšek-Olenik, M. Shamonin, and M. Jezeršek, “Laser Micromachining of Magnetoactive Elastomers as Enabling Technology for Magnetoresponsive Surfaces,” Adv. Mater. Technol., p. 2101045, 2022, doi: 10.1002/admt.202101045.

Presenting Author: Raphael Kriegl Ostbayerische Technische Hochschule Regensburg

Presenting Author Biography: Raphael Kriegl is a third-year PhD candidate in the Faculty of Electrical and Microsystems Engineering at Ostbayerische Technische Hochschule Regensburg, Germany.