Droplets covered by adsorbed particles are used in a wide range of research studies and applications, including stabilising emulsions used in the food or cosmetic industries, and fabricating new materials, such as microcapsules or multi-cavity structures. Pickering emulsions are commonly prepared by bulk emulsification techniques, for instance, by ultrasonic homogenisation or mechanical stirring, by membrane emulsification, or with the use of microfluidics. The latter two methods typically allow for more precise control of the droplet size distribution, whereas the bulk techniques guarantee high throughput. Here we propose a new bulk approach to fabricating Pickering emulsions by utilising electric fields. We prepare oil-in-oil emulsions stabilised by microparticles and control the mean size of the Pickering droplets. In our approach we take advantage of total surface area reduction of emulsion droplets by electrocoalescence. This leads to an increase in particle coverage, and eventually to formation of densely packed particle shells on Pickering droplets. First, we prepare an unstable pre-emulsion with droplets having small sizes and low particle coverages, from which the final Pickering emulsion is formed via consecutive coalescence events speeded up by application of electric fields. We monitor the development of the emulsions with optical microscopy imaging. The results demonstrate that the utilisation of electric fields goes beyond the mere role of enhancing coalescence; it plays an important role in surface particle manipulation and droplet rotation that further promote formation of stable particle-covered drops.

During hyperthermia, magnetite nanoparticles placed in an AC magnetic field become a source of heat. It has been shown that in fluid suspensions, magnetic particles move freely and generate heat easily. However, in tissues of different mechanical properties, nanoparticle movement is limited and leads to a small temperature rise in tissue. Therefore, it is crucial to conduct magnetic hyperthermia experiments in similar conditions to the human body. The effect of tissue-mimicking phantom compressibility on the effectiveness of magnetic hyperthermia was investigated on agar phantoms. Single and cluster nanoparticles were synthesized and used as magnetic materials. The prepared magnetic materials were characterized by transmission electron microscopy (TEM), and zeta potential measurements. Results show that tissue-mimicking phantom compressibility decreases with the concentration of agar. Moreover, the lower the compressibility, the lower the thermal effect of magnetic hyperthermia. Specific absorption rate (SAR) values also proved our assumption that tissue-mimicking phantom compressibility affects magnetic losses in the alternating magnetic field (AMF).

Hyperthermia treatment is the heating of tumor tissue up to temperatures between 41 ¥ C and 45 ¥ C, which trigger several physiological reactions in the body. Hyperthermia within tissue can be applied through various mechanisms. One of them is magnetic hyperthermia which uses superparamagnetic iron oxide nanoparticles (SPIONs) heated by an externally applied magnetic field. SPIONs can also be used as sonosensitizers in ultrasound hyperthermia increasing acoustic wave attenuation. The impact of SPION concentration on thermal effect during ultrasonic and magnetic hyperthermia was investigated in agar-gel phantom with added magnetite nanoparticles. The presence of nanoparticles in the tissue-mimicking phantom increases the thermal losses of ultrasound energy and temperature of the phantom.

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