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Universal process-inert encoding architecture for polymer microparticles


Polymer microparticles with unique, decodable identities are versatile information carriers with a small footprint. Widespread incorporation into industrial processes, however, is limited by a trade-off between encoding density, scalability and decoding robustness in diverse physicochemical environments. Here, we report an encoding strategy that combines spatial patterning with rare-earth upconversion nanocrystals, single-wavelength near-infrared excitation and portable CCD (charge-coupled device)-based decoding to distinguish particles synthesized by means of flow lithography. This architecture exhibits large, exponentially scalable encoding capacities (>106 particles), an ultralow decoding false-alarm rate (<10−9), the ability to manipulate particles by applying magnetic fields, and pronounced insensitivity to both particle chemistry and harsh processing conditions. We demonstrate quantitative agreement between observed and predicted decoding for a range of practical applications with orthogonal requirements, including covert multiparticle barcoding of pharmaceutical packaging (refractive-index matching), multiplexed microRNA detection (biocompatibility) and embedded labelling of high-temperature-cast objects (temperature resistance).

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Figure 1: Synthesis of encoded particles by stop-flow lithography.
Figure 2: Spectral characterization of UCNs.
Figure 3: CCD-based decoding of encoded particles.
Figure 4: Imaging of encoded particles with portable decoder in challenging settings.


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We thank J. Capobianco for thoughtful guidance and M. Garcia Fierro for critical reading and perspective on the manuscript. The MIT Lincoln Laboratory portion of this work was sponsored by the Department of the Air Force under Air Force Contract number FA8721-05-C-0002. The MIT Campus portion of this work was sponsored by the Office of the Assistant Secretary of Defense for Research and Engineering, the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the US Army Research Office, and the Singapore–MIT Alliance and National Science Foundation grants CMMI-1120724 and DMR-1006147. R.L.S. was supported by an NIH T32 GM08334 interdepartmental biotechnology training grant. The work was also supported by the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the US Army Research Office. The content of the information does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred.

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Authors and Affiliations



J.L. and P.W.B. contributed equally to this work. J.L. designed the research, conducted most of the experiments, conducted design and synthesis of UCNs, interpreted data and wrote the manuscript. P.W.B. conceived the project, designed experiments, interpreted data, conducted design and synthesis of UCNs, and wrote the manuscript. R.L.S. designed and conducted bioassay experiments. J.J.K. participated in design and synthesis of UCNs. P.S.D. and A.J.S. conceived the project, discussed the results, supervised the study and interpreted data. All authors reviewed and approved the manuscript.

Corresponding author

Correspondence to Patrick S. Doyle.

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Competing interests

The authors declare Provisional US patent applications 61/801, 351 and 61/800, 995, filed 15 March 2013.

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Lee, J., Bisso, P., Srinivas, R. et al. Universal process-inert encoding architecture for polymer microparticles. Nature Mater 13, 524–529 (2014).

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