The physics of the
red blood cell
Doctoral researcher in experimental soft-matter and biological physics at Saarland University. I study the mechanics, flow and aggregation of red blood cells, from single cells to dense suspensions, using in vivo microscopy, image analysis and physical modelling.
Background
Since 2022 I have been working towards a doctorate (Dr. rer. nat.) in the group of Prof. Christian Wagner at Saarland University. My Master's thesis dealt with the sedimentation of erythrocytes in colloidal-silica density gradients. My current work covers detection and tracking pipelines for microscopy data, 2D/3D image segmentation, shape analysis, and models of how red cells move, deform and aggregate.
The position is funded by a Young Investigator Grant awarded to Dr. Alexis Darras. In 2025 the work received the Best Poster Award at the Annual European Rheology Conference (AERC) in Lyon.
Selected projects
Figures are taken from the respective studies; references are given below each project.
Blood cells in vivo: tracking at vessel bifurcations
Detection and tracking pipelines for intravital microscopy. White blood cells are classified as rolling or flowing along the vessel wall and followed through bifurcations. In a second study, healthy and artificially rigidified red cells are compared at vessel junctions: rigid cells spend less time at the branch apex, which changes how blood is partitioned between the daughter vessels. This is relevant to diseases with stiffened red cells, such as malaria and sickle-cell disease. My contribution: video processing, tracking pipeline, data analysis, statistics and figures.
White blood cells: ongoing investigations with Khadija Larhrissi, AG Wagner.
Rigid versus healthy red cells: Rashidi*, Maurer*, Wrublewsky*, Larhrissi, John, Gidley, Toye, Kaestner, Wagner, Laschke, Darras. Biophysical Journal (2026). doi:10.1016/j.bpj.2026.03.023
Band patterns in density gradients
Centrifuged red cells settle into discrete bands, which were long interpreted as evidence of discontinuous cell ageing. Using a continuity equation that includes aggregation, we showed that the bands result from a competition between cell aggregation and net buoyancy. Related work explains the bands in classic Percoll gradients and the resulting limits of age separation.
Maurer, Romero, Lerch, John, Kaestner, Wagner, Darras. PNAS 122(51), e2515704122 (2025). doi:10.1073/pnas.2515704122
3D phenotyping of red-cell shape
Cell surfaces from confocal and STED stacks are smoothed by Willmore curvature flow and decomposed into spherical harmonics, which places each cell on the stomatocyte–discocyte–echinocyte axis. A random-forest classifier reaches 92% accuracy on 730 cells and separates shape changes that are difficult to distinguish by eye. Developed together with Nikolas Lerch.
Building on the 3D red-cell phenotyping of Simionato, Quint et al. AG Wagner, Saarland University.
Cytosol viscosity and density
Buoyant-density centrifugation gives the density distribution of red cells and, via the relation between cytosol viscosity and density, their intracellular viscosity. The results provide single-cell parameters for blood-flow models.
John, Kretsch, Maurer, Recktenwald, Kaestner, Wagner. Biophysical Journal 124(16) (2025). doi:10.1016/j.bpj.2025.07.002
Piezo1 activators: Yoda1 vs Yoda2
Automated patch clamp and calcium imaging are used to compare how the chemical activators Yoda1 and Yoda2 open the mechanosensitive Piezo1 channel in red cells.
Qiao, Penttinen, Coli, Murciano, Maurer, Wagner, Rotordam, Kaestner. Biomolecules 15(8), 1110 (2025). doi:10.3390/biom15081110
Red-cell shapes in time-dependent capillary flow
In capillary flow, red cells adopt either a symmetric croissant or an off-centred slipper shape. Under time-dependent flow, the croissant-to-slipper transition is considerably faster than the reverse and depends on the flow ramp rate. Cells were tracked in a co-moving frame using a custom PID-controlled microscope stage.
Recktenwald*, Graessel*, Maurer, John, Gekle, Wagner. Biophysical Journal 121(1) (2022). doi:10.1016/j.bpj.2021.12.009
THC and sickle red cells
Δ⁹-THC activates cation channels in red cells, which raises intracellular calcium and leads to dehydration and shape change. After THC exposure, a large fraction of sickle cells shifts into the high-calcium range, suggesting that cannabis use may be harmful in sickle-cell disease.
Hatem*, Esperti*, Murciano*, Qiao*, … Maurer, … Egée. American Journal of Hematology 98(12) (2023). doi:10.1002/ajh.27109
Deposits of drying blood droplets
Drying droplets usually leave a ring-shaped deposit (coffee-ring effect). At low red-cell concentration, the deposit instead grows from a central edge. This growth is quantified via interface growth and roughness scaling, with potential use in blood-drop diagnostics.
Sardari, Mohammadian, Asfia, Maurer, Örüm, … Darras. J. Colloid Interface Sci. 679(A) (2025). doi:10.1016/j.jcis.2024.10.039
Red-cell aggregation and gel formation
Ongoing work: optical-tweezers measurements of the attraction between two cells are used to derive a pair-interaction potential, which enters a percolation model of aggregated blood as a gel.
Ongoing, with K. Korneev and C. Haessig, AG Wagner. 3D reconstruction and recording of the cells shown by C. Haessig.
Peer-reviewed articles
* equal contributionRashidi*, Maurer*, Wrublewsky*, Larhrissi, John, Gidley, Toye, Kaestner, Wagner, Laschke, Darras
Biophysical Journal · doi:10.1016/j.bpj.2026.03.023DOI ↗ 2025Band pattern formation of erythrocytes in density gradients is due to competing aggregation and net buoyancy
Maurer, Romero, Lerch, John, Kaestner, Wagner, Darras
PNAS 122(51), e2515704122 · doi:10.1073/pnas.2515704122DOI ↗ 2025Viscosity and density measurements on the cytosol of human red blood cells
John, Kretsch, Maurer, Recktenwald, Kaestner, Wagner
Biophysical Journal 124(16), 2668-2676 · doi:10.1016/j.bpj.2025.07.002DOI ↗ 2025Piezo1 channel activators Yoda1 and Yoda2 in the context of red blood cells
Qiao, Penttinen, Coli, Murciano, Maurer, Wagner, Rotordam, Kaestner
Biomolecules 15(8), 1110 · doi:10.3390/biom15081110DOI ↗ 2025Deposit of red blood cells at low concentrations in evaporating droplets is dominated by a central edge growth
Sardari, Mohammadian, Asfia, Maurer, Örüm, Seemann, John, Kaestner, Wagner, Maleki, Darras
J. Colloid Interface Sci. 679(A), 939-946 · doi:10.1016/j.jcis.2024.10.039DOI ↗ 2023Adverse effects of Δ⁹-tetrahydrocannabinol on sickle red blood cells
Hatem*, Esperti*, Murciano*, Qiao*, Rotordam, Becker, Nader, Maurer, Pérès, Bouyer, Kaestner, Connes, Egée
American Journal of Hematology 98(12), E383-E386 · doi:10.1002/ajh.27109DOI ↗ 2022Continuous Percoll gradient centrifugation of erythrocytes: explanation of cellular bands and compromised age separation
Maurer, John, Makhro, Bogdanova, Minetti, Wagner, Kaestner
Cells 11(8), 1296 · doi:10.3390/cells11081296DOI ↗ 2022Red blood cell shape transitions and dynamics in time-dependent capillary flows
Recktenwald*, Graessel*, Maurer, John, Gekle, Wagner
Biophysical Journal 121(1), 23-36 · doi:10.1016/j.bpj.2021.12.009DOI ↗
Additional manuscripts in preparation. Full list on ORCID. Ad hoc reviewer (2023), Scandinavian Journal of Clinical & Laboratory Investigation.
Software
Research pipelines and teaching software, available on github.com/FelixMaurer.
Education and employment
Experimental soft matter / biological physics, AG Wagner · Saarland University.
Saarland University. Thesis: sedimentation of erythrocytes in a colloidal-silica density gradient.
Saarland University. Thesis: statistical analysis of red-cell flow in microchannels.
Saarland University · research & teaching. Funded by a Young Investigator Grant (A. Darras).
AspektEins GmbH · integrated systems, ARM firmware, PCB design (working student).
AG Wagner · microscope control, image analysis, portable optical tweezers.
Red-cell rigidity reshapes in vivo flow and lingering in bifurcations.Read ↗ 07 Jan 2026Solving the mystery of “blood-cell stripes”
Aggregation, not age, creates the centrifugation bands. (Saarland University)Read ↗ 22 Dec 2025Scientists unravel stripe patterns in nature
University of Bristol & Saarland University on red-cell aggregation.Read ↗ 19 Dec 2025Paper published in PNAS
Band pattern formation of erythrocytes in density gradients.Read ↗
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mail@felixmilanmaurer.com
Campus E2 6, Room 320
66123 Saarbrücken, Germany
+49 (0)681 302 - 2977
orcid.org/0000-0002-6459-1204
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