Isabelle Eisenmann

Hydrodynamic instabilities of active jets A continuum model is developed to analyze the stability of finite-size coherent structures in suspensions of strongly aligned swimmers. For dilute active jets, pullers undergo pearling instabilities w...

We detail the generalized theory as well as the long-term dynamics of the instabilities in the companion paper :
journals.aps.org/prfluids/abs...

Thanks to the brilliant Marco Vona, Eric Lauga and Takuji Ishikawa - and of course huge thanks to my advisors Raphaël and Nicolas!

A jet breaks into droplets that elongate into ellipses...in turn unstable to buckling, as soon as they are thin enough for one wavelength to develop. We end up with these structures that can also be understood through symmetry arguments - see this beautiful work: journals.aps.org/prl/abstract...

When C.reinhardtii cells swim one behind each other, they tend to pull on their neighbors, leading to a pearling instability. In contrast, when they swim side to side, they push on their neighbors, leading to a buckling instability. We control both by steering these phototactic cells with light.

Pure Hydrodynamic Instabilities in Active Jets of Puller Microalgae Using phototaxis to control cell orientation, various instabilities can be induced in jets of motile microalgae.

Our work on hydrodynamic instabilities in active jets is on the cover of PRL this week!
journals.aps.org/prl/abstract...

A dialogue between experiment and theory, where we use light to control active suspensions and show how they can be destabilized by their self-generated flows

🎧 Conseil podcast du weekend

Je conseille vivement les replays de cet excellent colloque du Collège de France qui explore la relation entre #genre et #sciences.

Bonne écoute !

🖱Disponible sur l'application Radio France, et sur www.college-de-france.fr/fr/agenda/gr...

See this nice summary in Physics Magazine (where I note an important difference between algae and penguins):
physics.aps.org/articles/v18...

A collaboration between physicists, biologists and chemists. Algae inside the dense phase are collectively protected from photodamage, showing that phototaxis can complement efficiently molecular photoprotective mechanisms on short timescales.

We show that the coupling between negative phototaxis and light absorption by the green algae destabilizes the suspension at critical cell densities/light intensities while the nonlocality of vision interactions explains the selection of a finite wavelength.

Happy to share that our work on active phase separation by photophobic microalgae is now published in PRL!
journals.aps.org/prl/abstract...

When surrounded by multiple light sources, cells hide behind each other, leading to the quick formation of a macroscopic branching pattern.

The myth of energy transition The concept of an “energy transition” is misleading, states the CNRS science historian Jean-Baptiste Fressoz. He explains why coal and oil never replaced wood, and that the fight against climate chang...

#CNRSnews 📰 Energy transition is a myth, based on the misconception that energy sources were replaced by “cleaner” alternatives over the past 200 years. Carbon emissions have actually increased, hence the need for better informed strategies to fight global warming
news.cnrs.fr/articles/the...

Upcoming Symposium!

Physics of Adaptation and Decision making in Biology!

When: September 16
Where: Amsterdam, The Netherlands
Join us here: www.fluidlab.nl/padm25

Speakers:
Ray Goldstein, Sujit Datta, @thomasshimizu.bsky.social, @mirnakramar.bsky.social, @blarson.bsky.social, me

The call is now officially open, with a deadline at the end of July! ⏳

If you are interested in applying, don’t hesitate to contact me. 🔬🦠

We are living the hottest June on record after infamous June 2003 🔥

At high elevation, consequences of lack of freezing are obvious: a lake has formed on the glacier at Punta Helbronner (~3300 m)
Crazy... not the first time, but it's a sign of how hot it gets at high altitude!

📸 @skywaymontebianco

🦠🔬 PhD positions available 🔬🦠

If you’re curious about light–matter interactions and collective behaviour in living systems, check out the attachment for more details.

📝 The official call will be published soon, but informal expressions of interest are already welcome!

I was surprised that the Compagnie du Mt Blanc doesn't mention climate change in their ~2h exhibition on Mont Blanc massif and mountaineering at the Aiguille du Midi.
Yet the station is covered with sensors to anticipate rock falls and weakening of the structure due to the melting of permafrost.

And finally, a picture from Irene Joliot-Curie's album (from a small exhibition outside the Curie museum in Paris). She took it in 1939 also in Mont Blanc massif, at the summit of Mt Tondu. In 2023 the Glacier de Tré-la-Tête has hugely receded

I was surprised that the Compagnie du Mt Blanc doesn't mention climate change in their ~2h exhibition on Mont Blanc massif and mountaineering at the Aiguille du Midi.
Yet the station is covered with sensors to anticipate rock falls and weakening of the structure due to the melting of permafrost.

..and the Glacier d'Argentiere, that will soon no longer be visible from the village (another old picture displayed at the school)

Here is another view of the Glacier des Bossons that I paired with the current picture.

Another picture displayed in the school shows the Glacier des Bossons as seen from Chamonix a century ago.

The school of physics was founded in 1951 by Cécile DeWitt-Morette, a French physicist then postdoc in the US.

This picture of the Mer de Glace, which is displayed in the school, was taken two years before; since then it has lost ~2,5km in length and 200m in thickness.

Les Houches! Thanks to the organizers and all the participants for a great week of Soft matter & Biophysics in this stunning place

A Lancet Editorial: “American chaos: standing up for health and medicine”

“...to care is an act not of weakness, but of strength.”

The Lancet response: bit.ly/4jRb5Av

wowww bravo Gianni! super happy for you!

Interplay between high-energy quenching and state transitions in Chlamydomonas reinhardtii: a single-cell approach https://www.biorxiv.org/content/10.1101/2025.01.23.633867v1