[23p-C205-1~11] 4.3 Lasers and laser materials processing

▲ [23p-C205-8] AFM Detection of Vibration Propagation in a Protein Microcrystal Triggered by Femtosecond Laser Impulse

〇(D)Po-Wei Yi^1,2, Yuka Tsuri¹, Kazuki Inoue¹, Teruki Sugiyama^1,2, Hiroshi Masuhara², Yoichiroh Hosokawa¹ (1.NARA Inst. of Sci. and Tech., 2.National Yang Ming Chiao Tung Univ.)

Keywords:Femtosecond laser impulse, Atomic force microscopy, Young's modulus

The femtosecond laser amplifier has received much attention as a promising tool for three-dimensionally processing and manipulating micro-sized objects. Especially the focused laser pulse with high peak intensity generates shockwave and stresswave effectively. We applied these waves as an impulsive force to evaluate surface elasticity of biological materials such as zebrafish embryos and biomimetic micro gel-sphere [1,2]. The responses of the mechanical vibration are monitored by the motion of the sample-attached atomic force microscopy (AFM) cantilever. This advanced technique enables sensitive detection of surface and internal elastic properties of biological materials. Herein, we have applied it to elucidate mechanical vibration propagation properties in protein microcrystals and evaluated the result in terms of Young’s modulus estimated from the AFM force curve measurements.
A single laser pulse from Ti:Sapphire femtosecond laser amplifier (800 nm, 150 fs, 1.5 μJ/pulse) was introduced into an inverted microscope at a distance from 10 μm to the edge of a lysozyme microcrystal. An AFM cantilever was placed on the top of one crystal with a size of about several hundred micrometers (Fig.1). Upon the single pulse irradiation, the vibration of the crystal was induced and its amplitude of the temporal profile was detected as the cantilever oscillations. As shown in Fig. 2, an apparent spike appears at t = 0 due to the direct scattering of the femtosecond laser to the photodiode in the AFM.