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Mechanical strengthening of fiberoptic microneedles using an elastomeric support.
MedLine Citation:
PMID:  22510991     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
BACKGROUND AND OBJECTIVES: Microneedles made from silica fiberoptics permit transmission and collection of light, which is an important functional advantage over metal or silicon microneedles. This added functionality may enhance or even enable new percutaneous light-based clinical diagnostic and therapeutic procedures. Micron-diameter fiberoptic microneedles, created from solid fibers capable of light emission and detection, are designed to penetrate several millimeters into tissue while minimizing tissue invasion and disruption. The mechanical strength (critical buckling force) of high aspect ratio (length to diameter) microneedles is a potential problem, which has motivated our invention of an elastomeric support device. In this study, we have tested our hypothesis that embedding the microneedles in an elastomeric support medium may increase microneedle critical buckling force. MATERIALS AND METHODS: The critical buckling force of silica microneedles with 55, 70, and 110 µm diameters and 3 mm lengths were measured with and without a surrounding elastomeric support (PDMS, polydimethylsiloxane). These experimental results were compared to theoretical calculations generated by the Rayleigh-Ritz buckling model. The insertion force required to penetrate ex vivo porcine skin was measured for microneedles with 55 and 70 µm diameters. RESULTS: Use of the PDMS support increased critical buckling force for microneedles of 55, 70, and 110 µm diameters by an average of 610%, 290%, and 33%, respectively. Theoretical calculations by the Rayleigh-Ritz model consistently overestimated the experimentally determined strengthening, but correlated highly with the greater enhancement offered to thinner microneedles. Aided by mechanical strengthening, microneedles 55 µm in diameter were able to repeatedly penetrate. CONCLUSIONS: The critical buckling force of microneedles can be increased substantially to allow extremely high-aspect ratio microneedles, 55-110 µm in diameter and 3 mm in length, to penetrate ex vivo porcine skin. By this strengthening method, the safety and reliability of microneedles in potential clinical applications can be considerably enhanced. Lasers Surg. Med. © 2012 Wiley Periodicals, Inc.
Authors:
Mehmet A Kosoglu; R Lyle Hood; Christopher G Rylander
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-17
Journal Detail:
Title:  Lasers in surgery and medicine     Volume:  -     ISSN:  1096-9101     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8007168     Medline TA:  Lasers Surg Med     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Wiley Periodicals, Inc.
Affiliation:
Department of Mechanical Engineering, Virginia Tech, Randolph Hall, 100L1, Blacksburg, Virginia 24061.
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