Chirality is an important property of matter. It is defined as a property of objects that cannot be superimposed to their mirror images through any combination of rotations or translations, much like the distinct left and right hands. In chiral crystals, the spatial arrangement of atoms gives rise to a specific handedness, with the crystal structure twisting along one propagation direction in a way similar to a screw. As a consequence, propagation in one direction, for example of an electrical current, may experience different resistance than that propagating in the opposite direction. This effect also influences certain chemical reactions and biological processes, which select for one specific handedness. In this sense, the ability to control chirality on demand, turning a right-handed structure into a left-handed one, is very desirable. 

Yet “unlike electrical polarization or magnetization, chirality has lacked a general physical handle for external control,” notes Zhiyang Zeng, first author of this study. The MPSD researchers have now shown that mechanical strain provides precisely such a handle. Rather than synthesizing a chiral material, they begin with a crystal that is not chiral in its unstrained state. Applying strain rearranges the positions of the atoms in the crystal just enough to create a left- or right-handed structure.

To demonstrate this effect, the team monitored the appearance of the crystal’s optical activity – a characteristic signature of chirality – while applying controlled mechanical strain. Remarkably, the handedness of the induced chiral state is determined by the strain conditions. Tensile and compressive strain generate opposite handedness, while applying strain along different crystal directions provides another way to select the resulting chiral state. “Because the deformation is reversible, the induced chirality can be generated, removed, and selected repeatedly,” explains Michael Först, co-author of this publication.

Beyond demonstrating the effect experimentally, the team established a theoretical framework that reveals when crystal symmetry allows this piezochiral effect to occur. They used it to compile an open-access database of candidate materials ( making it possible for researchers worldwide to search for and explore piezochiral crystals.

This work establishes a new strategy for engineering chirality. Instead of being permanently fixed by crystal growth or chemical synthesis, chirality can now be generated, controlled, and switched on demand in an originally achiral material. This is opening new opportunities to control mechanically reconfigurable materials. 

“We termed this phenomenon the piezochiral effect,” says Andrea Cavalleri, who led the research in Hamburg (in collaboration with Paolo Radaelli from the University of Oxford). “It enables one to induce chirality in substrates for a large variety of thin films or in bulk materials,  and may enable strategies to, for example, create new types of chiral properties such as superconductivity”.

This work received financial support from the Deutsche Forschungsgemeinschaft via the Cluster of Excellence ‘CUI: Advanced Imaging of Matter’. The MPSD is a member of the Center for Free-Electron Laser Science (CFEL), a joint enterprise with DESY and the University of Hamburg.

This pioneering work introduces a dual tilt-scan protocol designed for comprehensive tomography data collection within both real and reciprocal space. This methodological innovation facilitates the precise determination of the absolute structure of individual nanocrystals, a feat crucial for distinguishing between left- and right-handed enantiomorphs. Beyond just identifying chirality, the method estimates the volumetric contribution of each crystallite, enabling a quantitative assessment of enantiomorphic excess across bulk samples. This refinement addresses two critical bottlenecks in chirality analysis: the determination of absolute configuration and the estimation of relative abundance within mixtures.

The dual tilt-scan protocol operates by systematically tilting the crystalline specimen under an electron microscope, capturing diffraction patterns from multiple orientations. This comprehensive angular sampling allows the reconstruction of a three-dimensional reciprocal lattice, revealing nuanced details about the crystal’s symmetry and chirality. When combined with real-space tomography, researchers gain a multidimensional dataset that intricately maps the crystallographic and morphological features of each particle. This dual approach surpasses previously established techniques by integrating spatial and diffraction information into a single analytical framework.

Crucially, this method is adapted for high-throughput analysis through automated serial data collection. By rapidly acquiring data from hundreds of nanocrystals, the process becomes statistically robust and scalable, marking a transformative leap in how chiral solid-state materials are characterized. This scalability is particularly significant for industrial and pharmaceutical applications, where understanding chiral purity can directly influence the efficacy and safety of products. The capacity to analyze large ensembles of individual crystals ensures that observed enantiomeric ratios are representative of the bulk material rather than being skewed by isolated outliers.

The researchers validated this methodology on chiral inorganic nanocrystals, specifically addressing how chiral ligands—molecules bound to the surface of the crystals—can influence the bias towards one enantiomorphic form during synthesis. Their findings reveal a subtle yet fundamental interplay between molecular chirality at the ligand level and the resultant crystalline handedness, offering insight into the mechanisms controlling chiral amplification in nanoscale systems. This understanding could guide the design of synthesis strategies that favor the selective production of desired enantiomorphs, improving the performance and selectivity of chiral nanomaterials in catalytic or optical applications.

Expanding the scope of their investigation, the team demonstrated the exceptional robustness of their approach by applying it to an organic chiral drug, cinchonine. Such organic compounds frequently exist as racemic mixtures—equal parts of each enantiomorph—or with varying enantiomeric excesses, making stringent characterization vital for regulatory and therapeutic purposes. The ability to discern and quantify the chirality of nanocrystalline drug forms provides a powerful tool for pharmaceutical development and quality control, especially in cases where complete enantiopurity is challenging or unnecessary.

This multidimensional electron diffraction technique precisely overcomes limitations of conventional chiroptical spectroscopy or X-ray diffraction, which sometimes struggle to unequivocally assign absolute configurations or to handle nano- and microcrystalline powders effectively. Unlike bulk techniques that average over many domains or crystals, the method’s single-particle resolution unlocks granular details, ensuring that subtle differences between enantiomorphs are not obscured. This granularity is vital for novel materials where heterogeneous chiral domains might impact performance but remain undetected by less sensitive methods.

The integration of real and reciprocal space tomography also offers a novel visualization dimension to chiral crystal analysis. Researchers can now directly observe how geometric morphologies correlate with enantiomorphic identity, opening pathways for correlating physical shape, surface facets, and chirality in unprecedented detail. Such capability could facilitate deeper investigations into crystal growth dynamics or the influence of external fields and environments on chiral selection and stability.

From a technological standpoint, the dual tilt-scan protocol harnesses advances in transmission electron microscopy hardware and computational reconstruction algorithms. Automated tilt-series acquisition synchronized with diffraction pattern recording reduces manual intervention, minimizes electron beam damage, and optimizes data quality. The computational pipeline for reconstructing three-dimensional diffraction volumes and real space tomograms ensures rapid and reproducible analysis, a critical factor for adoption in routine characterization laboratories.

This methodology’s high-throughput nature is poised to catalyze further research into the fundamental aspects of chirality across materials science. Large datasets generated from hundreds or thousands of nanocrystals allow for statistically significant studies on how processing conditions, chemical environments, or ligand exchange processes influence chiral distributions. Consequently, the field can move towards predictive modeling and controlled synthesis of enantiopure or enantioenriched crystalline materials.

The potential implications extend beyond basic research. In catalysis, for instance, the precise tailoring of enantiomorphic surfaces might lead to catalysts with enhanced selectivity for one chiral product, reducing waste and increasing efficiency. Similarly, in photonics, chiral nanocrystals with controlled handedness can exhibit unique circular dichroism or optical rotation properties valuable for sensors and optical devices. The ability to quantitatively analyze and optimize these characteristics accelerates the transition from laboratory curiosities to commercial applications.

Moreover, the pharmaceutical industry stands to benefit immensely. Drug efficacy and safety often hinge on stereochemical purity, and regulatory agencies require rigorous characterization. The presented technique offers a survey-grade yet precise analytical tool to verify enantiomeric ratios at the nanoscale, supporting drug formulation, stability testing, and process validation. This capability is especially critical for polymorphic drugs, where different crystal forms possess distinct bioavailabilities influenced further by chirality.

On a conceptual level, this advance highlights the power of combining cutting-edge electron microscopy with sophisticated data acquisition protocols to address complexities in solid-state chemistry. By bridging the gap between atomic-scale structure and macroscopic properties, the approach redefines our capacity to interrogate and engineer chiral materials. It speaks to a broader paradigm shift, where multi-modal, high-resolution characterization methodologies are central in materials discovery and development pipelines.

The study thus represents a milestone in chiral materials science, equipping researchers with a versatile, quantitative, and efficient tool to unravel one of the field’s most elusive parameters—the enantiomorphic composition in polycrystalline samples. It challenges traditional boundaries, urging the community to rethink how chirality is measured, understood, and exploited across scientific and industrial domains. As these methods gain traction, they promise to shape the future landscape of chiral material design, synthesis, and application.

The work also sets the stage for subsequent innovations that might integrate complementary spectroscopic or computational techniques, further enhancing chirality analysis. Collaborative, interdisciplinary approaches combining chemical synthesis, electron microscopy, crystallography, and machine learning could soon emerge, leveraging this breakthrough framework for even more refined control over chiral matter.

In essence, the quantification of enantiomorphs through three-dimensional electron diffraction marks a transformative chapter in the study of chirality. It enables the rigorous study of chiral nanocrystals and organic solids at a level of precision and throughput previously unattainable, potentially influencing a wide spectrum of technologies—from catalysis to medicine. As researchers worldwide adopt and adapt this technique, we can anticipate a surge in discoveries and applications arising from a deeper, more accurate understanding of chiral crystalline materials.

Subject of Research: Quantitative analysis of chirality and enantiomorphic ratios in crystalline powders using three-dimensional electron diffraction.

Article Title: Quantification of enantiomorphs in chiral crystalline powders through three-dimensional electron diffraction.

Article References:
Hu, J., Dong, Z., Chu, C. et al. Quantification of enantiomorphs in chiral crystalline powders through three-dimensional electron diffraction.
Nat. Chem. (2025). https://doi.org/10.1038/s41557-025-01950-5

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