The functional properties of colloidal materials can be tailored by tuning the shape of their constituent particles. Unfortunately, a reliable, general methodology for purifying colloidal materials solely based on shape is still lacking. Here we exploit the single-particle analysis and sorting capabilities of the fluorescence-activated cell sorting (FACS) instrument, a commonly used tool in biomedical research, and demonstrate the ability to separate mixtures of synthetic microparticles based solely on their shape with high purity. We achieve this by simultaneously obtaining four independent optical scattering signals from the FACS instrument to create shape-specific ‘scattering signatures’ that can be used for particle classification and sorting. We demonstrate that these four-dimensional signatures can overcome the confounding effects of particle orientation on shape-based characterization. Using this strategy, robust discrimination of particles differing only slightly in shape and an efficient selection of desired shapes from mixtures comprising particles of diverse sizes and materials is demonstrated.
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Flow cytometry data are available as FCS files in FlowRepository with accession code FR-FCM-ZYR6. All the other data that support the findings of this study are available within the article and its supplementary information files or available from the corresponding authors upon reasonable request.
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We thank D. Wu, C. Gordon, C. Wang, P. Coffey and M. Radeke for helpful discussion and technical flow cytometry support. This work was financially supported by DARPA (N66001-14-2-4055). H.T.S. is a Chan Zuckerberg Biohub investigator. The content of the information does not necessarily reflect the position or the policy of the government, and no official endorsement should be inferred.
The authors declare no competing interests.
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Supplementary Discussion 1–2, Supplementary Figures 1–12, Supplementary Tables 1–2, Supplementary References 1–4
MATLAB code for simulating the forward scattering (FSC) and side scattering (SSC) intensities of spheres using Mie theory
Python code for simulating the forward scattering (FSC) and side scattering (SSC) intensities of ellipsoids using the T-matrix method
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Mage, P.L., Csordas, A.T., Brown, T. et al. Shape-based separation of synthetic microparticles. Nature Mater 18, 82–89 (2019). https://doi.org/10.1038/s41563-018-0244-9
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