Label-free, non-invasive mechanical imaging of living plant tissues in 3D
The Brillouin microscope at UPSC enables high-resolution, three-dimensional mapping of the mechanical properties of living plant cells and tissues without physical contact, labelling, or sample preparation. By measuring the interaction between light and acoustic vibrations inside a sample (the Brillouin shift, Fig. 1 A and B), this instrument provides direct, quantitative information on viscoelastic properties such as stiffness and compressibility at cellular and subcellular resolution.
Unlike surface-bound techniques such as atomic force microscopy (AFM), Brillouin microscopy captures mechanical information throughout the sample volume. It is particularly suited for studies where mechanical properties change dynamically, such as during growth, cell differentiation, or responses to environmental stress.
Principles of Brillouin microscopyFigure 1: Principles of Brillouin microscopy. A. The interaction of light from a laser (green) and sound (phonons, black arrows) causes light scattering. B. Depending on the mechanical properties of the sample, the scattered light will have different frequency and intensity. C. The Brillouin microscopy technique uses a confocal microscopy coupled to a Brillouin spectrometer to direct the laser light beam to a specific point of the sample, obtaining a measurement of the mechanical characteristics (stiffness) of this point with nanometric resolution. A and B adapted from Antonacci et al., 2020.
Instrument Overview
The system is based on the CellSense Discoverer™ Brillouin microscope, integrated with a Zeiss LSM 780 confocal microscope (Fig. 1C). It combines a fibre-coupled 780 nm laser with low phototoxicity, a multi-stage dispersive spectrometer, and an advanced sCMOS detector to deliver high-sensitivity measurements with a free spectral range of 15 GHz. This allows detection of subtle changes in mechanical properties, with continuous calibration ensuring precision and reproducibility across experiments.
The system operates fully automatically, from alignment and calibration to data acquisition and analysis, making it suitable for users without extensive optics experience. Data can be collected from a defined point, a two-dimensional area, or an entire three-dimensional volume, and correlated with optical or fluorescence images for structural and genetic context. 
Brillouin microscope at UPSC Applications
Applications
Brillouin microscopy is a powerful tool for plant mechanobiology and cell wall research. Its ability to image 3D mechanical maps non-invasively (Fig. 2) makes the Brillouin microscope particularly valuable for long-term live imaging and for studying structures where physical contact methods are unsuitable. At UPSC, it is used to:
- Quantify changes in cell wall stiffness and viscosity during growth and development.
- Monitor mechanical responses to environmental stresses such as salinity, drought, or temperature fluctuations.
- Investigate how genetic modifications affect tissue mechanics in crops and trees.
- Study mechanical signalling in processes such as cell adhesion, lateral root formation, or pathogen interaction.
- Correlate mechanical properties with fluorescent markers or structural features through combined Brillouin and confocal imaging.
While the system at UPSC is primarily used for plant science, Brillouin microscopy is increasingly applied across diverse areas of biology and materials research. Its label-free, contactless nature and high spatial resolution make it a versatile tool for:
- Cell biology: Measuring stiffness differences between cellular compartments or tracking mechanical changes during differentiation and morphogenesis.
- Organoid and tissue studies: Mapping viscoelastic properties in 3D to study tissue development, disease progression, or regeneration processes.
- Biomedical research: Characterising mechanical changes associated with fibrosis, tumour growth, or neurodegeneration in model systems.
- Materials science: Investigating mechanical properties of polymers, hydrogels, and bio-inspired materials at micrometre resolution.
These applications highlight the broader potential of Brillouin microscopy as a bridge between mechanics, biology, and materials science.
Technical Specifications
- Excitation source: 780 nm fibre-coupled laser, 200 mW output, frequency-stabilised with a Rubidium absorption cell
- Detection: Multi-stage dispersive spectrometer with cooled 4.2 MP sCMOS camera
- Measurement range: Free spectral range ≥ 15 GHz (Brillouin shift up to 7.5 GHz)
- Integration time: Millisecond range for live samples
- Compatibility: Fully integrated with Zeiss LSM 780 confocal microscope
- Software: Automated setup, calibration, and workflow-guided data acquisition and analysis
Access and Training
The Brillouin microscope is part of the UPSC microscopy facility located in room KB.K2 (B2.18.51) and available to both internal and external users. Training is provided by facility staff, and support is available for experimental design, data acquisition, and analysis.
For enquiries and bookings, please contact the UPSC microscopy platform or Laura Bacete