Almqvist N, Delamo Y, Smith B L, Thomson N H, Bartholdson A, Lal R, Brzezinski M, Hansma P K
Department of Physics, Luleå University of Technology, SE-971 87 Luleå, Sweden.
J Microsc. 2001 Jun;202(Pt 3):518-32. doi: 10.1046/j.1365-2818.2001.00887.x.
The mechanisms behind natural nanofabrication of highly structured silicas are increasingly being investigated. We have explored the use of a standard Nanoscope III Multimode atomic force microscope (AFM) to study the silica shell of diatoms. The delicate structures of the shell surface of the diatom Navicula pelliculosa (Bréb.) Hilse were imaged and the shell's micromechanical properties were measured semi-quantitatively with a resolution down to approximately 10 nm. The technique to measure elasticity and hardness with the AFM was demonstrated to be useable even on these hard glass-like surfaces. Different experimental configurations and evaluation methods were tested. They gave a consistent result of the shell micromechanical properties. The first results showed that the diatom shell's overall hardness and elasticity was similar to that of known silicas. However, regions with different mechanical properties were distinguished. The elastic modulus varied from 7 to 20 GPa, from 20 to 100 GPa and from 30 to hundreds of GPa depending on the location. In general, the hardness measurements showed similar spatial differences. The hardness values ranged from 1 to 12 GPa but one specific part of the shell was even harder. Hence, certain localized regions of the shell were significantly harder or more elastic. These regions coincide with known characteristic features and mechanisms appearing at the different stages of the shell's growth. These results show that this method serves as a complementary tool in the study of silica biomineralization, and can detect eventual crystalline phases.
高度结构化二氧化硅自然纳米制造背后的机制正越来越多地得到研究。我们已探索使用标准的Nanoscope III多模式原子力显微镜（AFM）来研究硅藻的二氧化硅外壳。对pelliculosa硅藻（布雷布.）希尔塞外壳表面的精细结构进行了成像，并以低至约10纳米的分辨率对该外壳的微机械性能进行了半定量测量。结果表明，即使在这些类似硬玻璃的表面上，用AFM测量弹性和硬度的技术也是可行的。测试了不同的实验配置和评估方法。它们给出了关于外壳微机械性能的一致结果。初步结果表明，硅藻外壳的整体硬度和弹性与已知二氧化硅的硬度和弹性相似。然而，可以区分出具有不同机械性能的区域。根据位置不同，弹性模量从7吉帕到20吉帕、从20吉帕到100吉帕以及从30吉帕到数百吉帕不等。一般来说，硬度测量显示出类似的空间差异。硬度值范围为1吉帕到12吉帕，但外壳的一个特定部分甚至更硬。因此，外壳的某些局部区域明显更硬或更具弹性。这些区域与外壳生长不同阶段出现的已知特征和机制相吻合。这些结果表明，该方法可作为研究二氧化硅生物矿化的补充工具，并能检测最终的晶相。
