Schematic illustration of the SU-8 microneedles. (a) Top view of the device structure. (b) A 5×5 SU-8 microneedles array. (c) Cross section of the device structure. (d) Single microneedle structure.
Fabrication process for SU-8 microtubes.
(a) Schematic illustration of the homemade stage to ensure flat SU-8 membrane surface. (b) SU-8 membrane bends after development. (c) After bonded with PDMS and clamped in the stage, the membrane becomes flat.
Fabrication process for maltose tips. (a) Expelling water at 140 °C. (b) Immersing microtubes into the maltose at 140 °C. (c) Drawing the tips at end of the microtubes when the temperature increases up to 160 °C. (d) Increasing drawing speed to form sharp tips.
(a) Optical image for the finished SU-8 microneedles. (b) Detailed illustration image for the microneedles array.
(a) Testing setup for the microneedle mechanical testing. (b) A typical microneedle stiffness testing result.
Penetration testing results on the porcine cadaver skin.
Maltose tips dissolving process. (a) The original sharp maltose tip. (b) Maltose tip after inserted into skin for 3 min. (c) Maltose tip after inserted into skin for 6 min. (d) Maltose tip after inserted into skin for 9 min.
Images of confocal microscopy of the site where one microneedle inserted shows that the fluorescent solution is delivered into the tissue underneath the skin surface. Optical section depths are (a) 30 μm, (b) 60 μm, (c) 90 μm, (d) 120 μm, (e) 150 μm, and (f) 180 μm below the skin surface.
Ratio of individual maltose tips to clustered maltose tips among a 5 × 5 microneedles array.
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