Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Typical SiO2 microneedles with (a) circular tip and (b) triangular tip additionally fabricated by FIB etching. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Batch fabrication process for an array of SiO2 microneedles with sharp tip: (a) SiO2 patterning, (b) DRIE, (c) oxidation and backside etching, and (d) formation of microneedles. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. An array of hollow SiO2 microneedles with root diameter of 7.5μm, length of 55μm, and tip radius of less than 0.5μm. (a) microneedle array with sharp tip and (b) sharp-tipped microneedles with aperture. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Overview of apparatus, which consists of a piezoelectric stage for fine feeding of microneedles on a rotation stage, a piezoelectric element for a mechanical oscillation, and a tilt stage on a coarse feeding stage for placement of insertion, for investigation of mechanical stability and needle insertion performance. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. A series of photographs where an array of microneedles (3.5-μm i.d., 5.5-μm o.d., 50-μm length, and 26-μm pitch) was fully inserted into gelatin and then pulled out: (a) before insertion, (b) during insertion, (c) during pullout, and (d) after insertion. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Typical FEM simulation result showing tensile stress distribution of microneedle (3.5-μm i.d., 5.5-μm o.d., and 100-μm length), where a bending force of 500μN was applied at a distance of 70μm from the needle root. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Variation of maximum tensile stress and defection of the needle (70μm in length) with applied force. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Effects of needle length on calculated maximum bending force and deflection required for fracturing needles. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Experimental bending fracture test of microneedle (3.5-μm i.d., 5.5-μm o.d., 77-μm length, and 26-μm pitch): (a) applied transverse force for bending and (b) typical fracture surface. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Results of experimental fracture tests where bending force was applied to needles: (a) Relation between maximum deflection without fracture and applied force position equivalent to needle length. (b) Maximum tensile stress and strain obtained from FEM analysis. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Displacement of insertion as a function of outer diameter of microneedle tip, where insertion speed is 2.5μm∕s, needle length is 50μm, and thickness of SiO2 is about 1μm. The number of needles is 1016, 112, 1196, and 494, with outer diameter 1.4 (sharp- tipped needle, black square on white background in figure), 6.1, 8.3, and 14.6μm, respectively. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Displacement of insertion as a function of insertion speed of microneedles with inner diameter of 3.3μm, outer diameter of 5.9μm, and length of 45μm. The concentration of gelatin was 20wt%. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Needle insertion force and calculated needle insertion stress as a function of surface area of microneedle tip. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /

Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Displacement of insertion into 5wt% and 20wt% gelatin as a function of frequency applied to microneedle with outer diameter of 5.9μm, inner diameter of 3.3μm, and length of 45μm, where the mechanical oscillation of the needle with an amplitude of 0.6μm was applied by the piezoelectric element, as shown in Fig.. Figure Legend: From: Mechanical characterization and insertion performance of hollow microneedle array for cell surgery J. Micro/Nanolith. MEMS MOEMS. 2009;8(3): doi: /