Publication

Illumination patterning techniques for optical sectioning in a wide-field microscope allow for maintaining good temporal resolution while improving image quality. Among these, two techniques are particularly widespread: structured illumination and line-confocal imaging. Until now, however, the relationship between the quality of optical sectioning and illumination parameters (wavelength, numerical aperture, illumination pattern) was not straightforward and relied on complex numerical calculations.

By deriving simple analytical formulas and comparing them to experimental data, this new work published in Biomedical Optics Express permits to accurately predict and optimize the quality of the axial sectioning and to determine which approach will provide the best images depending on the type of sample being studied, in particular in terms of signal-to-noise ratio.

For more information, have a look at the scientific article in Biomedical Optics Express.

• Read more about A simple-to-use analytical guide to optical sectioning with patterned illumination

The LAME (Lasers, Molecules, and Environment) team at LIPhy has acquired a frequency comb (Menlo Systems FC1500-ULNnova), a light source whose name refers to its spectrum composed of regularly spaced lines. This state-of-the-art equipment represents an investment of 350 k€, funded by the REFIMEVE network, UGA, CNRS, LIPhy, and the LAME team. This type of source is equivalent to millions of optical tuning forks whose frequencies are precisely known and cover a range extending from the infrared (2.1 µm) to the visible (500 nm), and allows for the extremely precise calibration of the frequency of any laser within this range.

At the same time, LIPhy becomes a key node in the REFIMEVE network, a research infrastructure that distributes ultra-precise time and frequency references across Europe via the telecom fiber network. The fact that the frequency comb and the network node are located in the same place offers a dual mutual benefit.

• On the one hand, this improves the quality of the REFIMEVE signal coverage, which is initially generated at the Laboratoire Temps Espace (LTE, Paris) using atomic clocks but degrades as it propagates over hundreds of kilometers and must therefore be reprocessed at various points in the network.
• On the other hand, this stabilizes the spectrum emitted by the frequency comb, thereby providing LIPhy with laser sources whose frequency is extremely stable and known with high precision in absolute terms. For example, an innovative source, funded by the FIRST-TF Labex and locked to the comb, produces a laser beam with a frequency of 473612337576230 Hz (corresponding to a wavelength in vacuum of 632.991234 nm) equivalent to that of a He-Ne laser, but with a spectral width of less than 5 kHz—making it 200 times better—and long-term stability guaranteed to be better than 10 Hz!

Having laser sources with high spectral purity that are properly calibrated is absolutely crucial for metrology experiments conducted in the laboratory. Within the LAME team, this enables, for example, measurements of isotopic ratios essential to geosciences, of spectral line profiles underlying satellite measurements, of THz spectroscopy for astrophysics, and of quantities of fundamental interest. These state-of-the-art laser beams are also intended to be distributed to neighboring laboratories, such as the Institut des Géosciences de l'Environnement (IGE) via the ERC DocPAST project, as well as to all LIPhy experiments that can benefit from them, such as the interferometers of the dynamic Surface Force Apparatus developed by the MODI team, which enables the study of the behavior of confined fluids at the nanoscale.

• Read more about LIPhy acquires a frequency comb referenceable to the REFIMEVE network

An overview of the topic is provided in this article published in CNRS Le Journal.

• Read more about Elucidating the mechanisms of cell motility

For more information, see the article posted on the Focus Sciences blog.

• Read more about Understanding ions to improve metal recycling

This striking behavior arises because the droplet surface freezes into a thin crystalline nano-shell that bends like a tiny hexagonal pita (a pocket-like flatbread), adopting a six-pointed star profile upon inflation of its interior, or shinking of its surface. Unlike conventional origami, where folding occurs along fixed crease lines, the folds of the inflating hexapita are mobile : they slide across the interface as the droplet deforms, continuously reshaping the star. The resulting hexagram, a symbol shared across cultures, emerges from the interplay of interfacial thermodynamics, geometry, topology, and elasticity. By revealing this nanoscale, mobile-fold origami mechanism, the work opens new routes for designing complex-shaped colloids and nanoparticles. It suggests that similar folding principles may operate in biological systems, playing role in morphogenesis of complex organisms, such as six-pointed star-like bacteria, and beyond.

For more information, have a look at:

• the scientific article in Physical Review Letters,
• the science outreach articles published in Physics Magazine, Chemical & Engineering News, Phys.org, EurekAlert!, Scienmag, Bioengineer.org, The Silicon Review & Life Technology.

• Read more about Liquid Origami and the Six-Pointed Star

For more information, check out the news published by the CNRS.

• Read more about The environmental transition is taking root at the CNRS, and LIPhy is contributing to it!

For more information, visit:

• the news on the UGA and CNRS Physique websites,
• the scientific paper published in Proceedings of the National Academy of Sciences.

• Read more about Ionic liquids: patience and time resolve more than ten years of scientific controversy

Measuring the signal reported by fluorescent biosensors based on the Förster Resonance Energy Transfer (FRET) principle is complex using a standard fluorescence microscope. Indeed, it requires measuring fluorescence intensity across three different channels and correcting the inherent biases of this technique. To address this, the QuanTI-FRET method proposed a protocol to calibrate the entire experimental setup and demonstrated absolute FRET signal measurement [1]. This calibration relied on FRET standards, whose preparation proved to be potentially cumbersome.

We propose to leverage the intrinsic properties of these biosensors to calibrate directly from the images of interest, thereby avoiding the additional step involving FRET standards. The application of this self-calibration concept is demonstrated in a scientific article [2]. To enable all research teams to benefit from this simplified yet still quantitative method, we have developed a publicly available Python analysis code [3] and also integrated it as a plugin for the open-source microscopy software Napari [4]. The method is thus usable without any knowledge of Python, simplifying both the experimental protocol and the analysis of FRET biosensors while maintaining unbiased quantitative results.

More information on the dedicated webpage.

[1] A. Coullomb, C. M. Bidan, C. Qian, F. Wehnekamp, C. Oddou, C. Albigès-Rizo, D. C. Lamb & A. Dupont. QuanTI-FRET: a framework for quantitative FRET measurements in living cells. Sci. Rep. 10, 6504 (2020)

[2] J. Leblanc, A. H. Lombard, A. Saumureau, S. Costrel, J. Revilloud, A. Coullomb & A. Dupont. Live-cell quantitative FRET imaging made simple by autocalibration in QuanTI-FRET. Eur. Phys. J. E 48, 74 (2025)

[3] https://gricad-gitlab.univ-grenoble-alpes.fr/liphy/quanti-fret

[4] https://napari-hub.org/plugins/quanti-fret.html

• Read more about Release of a free software for easy and quantitative FRET analyses

This new step toward understanding the development of (extra)terrestrial life has been published in Nature Communications.

For more information, visit:

• the news on the CNRS Chimie website,
• the scientific paper published in open access in Nature Communications.

• Read more about The revealed fragility of extremophile bacteria

After two weeks without watering, the plant seems to desperately cry for help, showing leaves completely falling on the ground… Fortunately, such a state is reversible, and the plant soon recovers its shape after watering!  What is so specific about this plant?

Anatomically, the petioles attaching the leaves to the ground behave as a hinge: they a U-shape section instead of a round shape, and contain a lot of water rich soft tissue. When the plant is dry the U-shaped base strongly bends; this is analogous to the bending of a carpenter's tape folding under sufficient load, except that the transition we observe here is slower.

Inspired by these observations, we introduce a biomimetic hinge: it is a rubber ribbon containing cavities whose U-shape section can be changed by pneumatic pressure. It offers a programmable bending stiffness and can suddenly bend under load reproducing the plant phenomenon.

For more information, have a look at:

• the scientific article in Quantitative Plant Biology,
• this short video for the general public on the LIPhy YouTube channel.

• Read more about A very expressive plant: Spathiphyllum reactions to water stress