Characterization of the mechanical behavior of SU-8 at microscale by viscoelastic analysis

Abstract

The mechanical properties of SU-8 at microscale were measured under both micropillar compression and nanoindentation on a film on a substrate. To the best of our knowledge, this paper reports the first set of results for microcompression of SU-8 micropillars for measurement of mechanical properties using viscoelastic analysis. The effects of loading rate and micropillar size are examined. It was determined that the SU-8 exhibits viscoelastic properties at room temperature, the time-average Young's modulus increases in general with the loading rate. The average Young's modulus determined by compression of a micropillar was 4.1 GPa at a strain rate near 10 −3 s −1 . For nanoindentation on a SU-8 film supported by a silicon substrate, the default output from the nanoindenter for the Young's modulus was approximately 6.0 GPa with the consideration of elastic-plastic behavior of the SU-8. When the viscoelastic effects were considered, the time-average Young's modulus at a given strain rate was determined to be near 3.6 GPa, which agrees with the reported values in the literature obtained from tension and bending, and also correlates reasonably well with data from microcompression. This work indicates that viscoelastic analysis is necessary to extract the valid mechanical properties at nano/microscales for SU-8.

Viscoelastic Characteristics of Mechanically Assembled Three-Dimensional Structures Formed by Compressive Buckling

“…The material was assumed to be a photopatternable epoxy [24]. gx 0 is assumed to be a constant to simulate the viscoelastic damping effect of Kelvin-Voigt model based on the data obtained by dynamic mechanical analysis, creep and stress relaxation, and other methods [49,53,54,75,76]. The vibrational displacement and velocity under the harmonic external load were obtained by the steady-state analysis, after importing the shape and stress of the buckled ribbon determined from the post-buckling analysis.…”

“…The viscoelastic properties can be characterized by dynamic mechanical analysis [49] and creep and stress relaxation methods [50] for a wide range of materials, such as poly(methyl methacrylate), SU8 epoxy resin, polypropylene, polydimethylsiloxane, etc. [51][52][53][54][55]. The viscoelastic damping effect due to viscosity of materials in a vibration system can be characterized by the half bandwidth n or the quality factor Q (Q ¼ 1= 2n ð Þ) [56][57][58].…”

Electron beam lithography fabrication of SU-8 polymer structures for cell studies

“…36 Diffusion of the photo-acid generator contributes to a general broadening of the exposed structures. 37,38 SU-8 is stiff with a Young's modulus reported in the range from 0.9 GPa to 7.4 GPa, 32,39 its processing is well established, 40 it has high chemical stability 39 and it is known to be bio-compatible. 41 High resolution, high aspect ratio combined with rapid fabrication time due to very high sensitivity 42 makes SU-8 EBL fabrication a promising approach for further exploration as structural component in structured cellular substrates.…”

Development of experimental methodology on fracture toughness of microscale polymer resins under in situ observation

“…Then, the evaluation technique for the strength of small resin components in the scale of micro/nanometer become more and more important. Although there have been conducted many research works on the strength of resin in macroscale, there are few works done on materials in the microscale …”

“…Although there have been conducted many research works on the strength of resin in macroscale, [3][4][5][6][7] there are few works done on materials in the microscale. [8][9][10] The fracture toughness, which gives the resistance for cracking, is a key factor in the design with high reliability. For micro/nanosize component with a crack, the size of the singular stress field region near the crack tip is in nanometer scale, and the material strength must be characteristic.…”