Research

Solute gradients regulate condensate motion

Biomolecular condensates in cells or synthetic applications are subject to complex chemical environments, including various concentration gradients. 

We investigate the motion of phase separated liquid droplets in gradients of other chemical species. We identify two different propulsion mechanisms: Chemical drift, driven by diffusive fluxes, and Marangoni flows, driven by differences in surface tension. 

How do chemical gradients affect surface tension of multi-component interfaces? What transport mechanism dominantes in what environment? How can we control the distribution of droplets in a system?

To answer these questions, I am using field based simulations and analytical techniques to find the relevant mechanisms that drive the propulsion of condensates.

Response function of ERK-signaling in HeLa cells

Supervised by Kazuhiro Aoki at the NIBB in Okazaki, Japan, we measured the transfer function of the EGFR-Ras-ERK signaling pathway in HeLa cells by way of ERK-KTR, a biosensor visualizing ERK activity by translocation to the nucleus, while activating ERK at different levels of the signaling pathway with microfluidic and optogenetic techniques.

We found oscillating ERK activity as a reaction to single short excitations of the pathway.  The final goal will be to extract a minimal network model of the pathway by means of data regression.

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Free energy principle of the brain

The brain is the most complex organ in our body. It constantly processes information and generates models of the world around us. It has been suggested that this predictive processing minimizes a functional akin to the thermodynamic notion of a free energy.

As part of a small interdisciplinary research group, supported by the German Academic Scholarship Foundation, we explore the utility of a Unified Theory of the Brain based on the so called Free Energy Principle (Karl Friston, 2010).

Supervised by Michael Kohl, we explored the theory and applications of the Free Energy Principle (FEP) through Literature and discussions with leading experts in the fields of neuroscience, computer science and philosophy. We particularly focused on the potential applicability of this abstract concept to laboratory experiments and evaluated its practical usefulness.

Topological defects in ferromagnetic superconductors (Master Thesis)

Usually, ferromagnetic order suppresses superconductivity due to strong magnetic exchange interactions. However, in superconducting iron pnictides such as EuFe2(As1−xPx)2  the onset of ferromagnetism can lie below the superconducting transition, enabling coexistence.

Supervised by Alexei Vagov and Vollrath Martin Axt, and in collaboration with Tiago T. Saraiva, I developed a theory of coexisting ferromagnetism and superconductivity. I analyzed the formation of magnetization patterns in such materials, using linear stability analysis and methods from nonlinear analysis like Amplitude equation formalism.

Finally, I was able to predict the existence and motion of topological Y-shaped defects in the magnetization-stripe-pattern that were subsequently found in experiments. I analyzed their velocity and connected it to important material parameters.

Temperature dependence of surface plasmon dispersion (Bachelor Thesis)

In my Bachelors project, supervised by Vollrath Martin Axt, I explored the dispersion of surface plasmon polaritons. These are quasi-particles, arising from a coupling between electromagnetic waves and collective electron motion at the interface of a (semi-)conductor.

I solved Maxwell's equation coupled to the electronic response function for different simple surface geometries and found that a temperature increase leads to an increased group velocity for small wave-lengths and an increased damping. We also found that for certain geometries (wave-guides), we can achieve a group velocity of zero for very large wave-lengths, that are excitable with light or quantum emitters.

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Granular impact in microgravity

Understanding how granular materials behave in microgravity is crucial for many engineering applications, including construction work and even spacecraft landings on asteroids.

This project, lead by Kai Huang, aimed to understand the impact characteristics of projectiles shot into granular matter, specifically under microgravity conditions. It also highlights methods to measure the trajectory of the projectile, without relying on optical imaging. Instead we used an IMU (Inertial Measurement Unit) that recorded tri-axial acceleration and angular velocity data.

As a student I developed analysis software to integrate the acceleration and angular velocity data to obtain the trajectory. Subsequently, I analyzed the IMU data from projectiles shot into granular matter in microgravity conditions (Drop Tower Bremen).

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