Tham khảo tài liệu 'bio-mems technologies and applications - wang and soper (eds) part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 332 Bio-MEMS Technologies and Applications a b c FIGURE SEM photomicrographs of surface micromachined microneedles a a metallic microneedle with multiple output ports b cross-section of the microneedle showing its microchannel c a sophisticatedly designed single microneedle with a shaft length of 500 pm. 2007 by Taylor Francis Group LLC MEMS for Drug Delivery 333 d FIGURE continued SEM photomicrographs of surface micromachined microneedles d an array of the microneedles with a center-to-center distance of 2 mm. From S. Chandrasekaran J. Brazzle and B. Frazier J. of Microelectromechanical Systems 12 289-295 2003 and S. Chandrasekaran and B. Frazier J. of Microelectromechanical Systems 12 281-288 2003. With permission. Out-of-Plane Silicon Microneedles One of the major issues with respect to in-plane microneedles is their limited density. This is due to the fact that only a one-dimensional array of microneedles can be microfabricated in a wafer. In order to achieve two-dimensional arrays of microneedles a complex microassembly process similar to one demonstrated by Bai et al. 6 would be needed. With the typical microneedle inner diameters of 10 to 100 pm the limited density of the microneedles may become an issue when delivering a large amount of a drug or in blood analysis applications which typically require a fair amount of blood. In addition shear stress created by the tissue during insertion may cause mechanical fracture for the single microneedle or one-dimensional array of long microneedles. The out-of-plane microneedle array appears to be a viable option for addressing the aforementioned issues because many microneedles can be microfabricated in a wafer and the two-dimensional arrays are less prone to fracturing when exposed to shear forces during penetration. The first demonstrated out-of-plane microdevices for drug and gene delivery are sharp solid silicon structures 16 17 . Dizon et al. realized an array of sharp solid silicon structures .
