Extended Data Fig. 9: Evaluation of information encoding and decoding with OPMR MNPs.

(a) A 17×17 pattern demonstrates the feasibility of recording billions of different patterns. Eight bits in each corner were assigned for patch orientation. An encrypted pattern was generated for encoding. A mask was fabricated using laser cutting. QD fluorescent dyes were selectively loaded to the PDMS negative mold. Patterned MNP was demolded from mold. The patterned MNP was applied to rats for long-term OPMR evaluations. (b) Encoded information on a microneedle patch can be simple (e.g., vaccine type, manufacturer, LOT/batch number, vaccination year and month), or complex (e.g., drug package inserts, active ingredient, warnings and precautions, prescribing information). Our current strategy of storage uses information bits as indexing numbers to encode 1) medical information by separating 37 bits into blocks, of which each is an index for a piece of information, or 2) unique identifier for each patient, which can cover the entire world’s human population and tens of generations after that with a 1.7 cm x 1.7 cm MNP. We can also use these indexing numbers to look up a library of hundreds of pages of documents. The information to encode can be determined as per use case while maximizing the usage of the on-patient bits. (c) Encodability can potentially be enhanced by utilizing each pattern as a ‘data matrix’, which assigns a serial number per pattern that can be linked to an online page. With the ‘data matrix’ approach, 1.1 trillion different serial numbers can be encoded with a 12 x 12 patch. (d) Five randomly selected representative 17×17 patterns are shown as examples. (e) Application and imaging of MNP on a rat using our custom applicator and imaging system. (f) 17×17 OPMR MNP encoding for ‘35-52-123456-03-08’ was decoded correctly for a 6-month monitoring period. The number of error bits fluctuate over the course of monitoring period due to rat skin irritation, rat fur interfering with the signal, and other environmental factors, but these error bits are successfully corrected with RM ECC.