Analytical and Numerical Approaches for Optimization Design of MEMS Based SU-8 Microneedles Nhut Tran-Minh 1,2,* , Hoa Le-Thanh 1 , Frank Karlsen 1 1 Vestfold University College, Postboks 2243, N-3103 Tonsberg, Norway 2 Norchip AS, Industriveien 8, N-3490 Klokkarstua, Norway Nhut.Tran-Minh@hive.no Hoa.Le.Thanh@student.hive.no Frank.Karlsen@hive.no Abstract. This paper addresses the optimization design of the MEMS based SU-8 microneedles for blood extraction by studying the effects of axial and transverse force on SU-8 microneedles during skin insertion in both analytical and numerical points of view. The critical buckling load and maximum bending force that the needle can withstand are 4.486N and 0.123N for 1200μm length (300μm x 300μm) needle, respectively. As the results of numerical simulation, the maximum stress 1.0719MPa, which occurs at tip, is smaller than 34MPaof yield strengthof SU-8. The bending test is also proved by applying the force of 0.1N on the tip of needle, resulting 33.8MPa of maximum stress which is com- parable to 34MPa of yield strength of SU-8. Base on these results, the numeri- cal simulation also proves that the needle with our design is strong enough for inserting into human skin. Keywords: SU-8, microneedles, blood extraction, skin insertion. 1 Introduction The ideal of microneedle has been known as a promising, painless approach com- pared to traditional technique using steel needle for both drug delivery and blood extraction. Since the concept of microneedle was introduced, the applications of mi- croneedle are either extraction or injection of biological components or drug for med- ical purposes. However, there are just only a few studies of microneedle on blood extraction purposes compared to drug delivery applications due to the limitation in fabrication techniques for long microneedle design. It is said in [1] by Chaudhri et al. that the proposed length of microneedle for delivery drug into human body is from 300μm to 700μm while it is needs to be much longer than in order to reach the blood vessel. Previously, the microneedles for delivery of drug are classified based on the fabri- cation technologies and needle materials with numbers of research in this field. For example, it can be based on the diffusion of drug with microneedle coated with drugs [2-4], improvement of drug infusion into the skin with hollow microneedle or the