Extended Data Fig. 4: Vaccine loading methods and MNP throughput.

(a) Schematic of the processes used for (a) one-step loading and (b) two-step tip-loading. A solution containing the vaccine and polymer is first dispensed using a robotic arm above the PDMS mold. Simultaneously, a vacuum of –1 bar is applied below to load the solution into the negative mold. Then, then solution is dried under desiccant atmosphere and –0.6 bar vacuum. For one-step loading (a), vaccine and enough polymer to form tips and backing are deposited in one step. For two-step tip-loading (b), vaccine and polymer are first deposited in the tips only, and then the same procedure is repeated using only polymer to form the backing of MNPs. (c) Characterization of correctly-formed full length, sharp microneedles fabricated by the automated MVP, as a percentage of total needles produced (n = 30 patches). MNPs fabricated had on average 37 ± 8 needles per patch. (d) Dispensing throughput is a function of dispensed drop height and patch size, while (e) drying throughput is a function of drying time and number of needles per patch. Both throughputs are functions of (f) drying time and (g) patch size. The step with the lowest throughput determines the overall throughput of the microneedle vaccine printer.