Fully angularly resolved 3D microrheology with optical tweezers
Fully angularly resolved 3D microrheology with optical tweezers
复制标题
DOI：
10.1007/s00397-024-01435-1
复制
发表时间：
2024-02-08
期刊：
影响因子：
2.3
通讯作者：
Tassieri，Manlio
中科院分区：
文献类型：
--
作者：
Matheson，Andrew B.;Mendonca，Tania;Tassieri，Manlio
光镊微流变学（MOT）是一种全光学技术，允许用户在微观尺度上研究材料的粘弹性，特别适用于具有复杂微观结构的材料，如生物样品。MOT越来越多地与3D成像系统和颗粒跟踪方法一起使用，以生成不仅显示样品中不同点之间的特性如何变化，而且还显示单个点处的粘弹性特性如何随方向变化的图。然而，由于聚焦光束的衍射限制形状，光学陷阱在3D中固有地是各向异性的。这可能导致在某些方向上流体粘度的显著高估。因此，流变性质只能沿平行于或垂直于阱光束传播轴的沿着方向精确探测。在这项工作中，一种新的分析方法被证明可以克服这种潜在的人为因素。这是通过对3D MOT数据进行主成分分析来实现的，以识别陷阱，然后识别陷阱各向异性影响数据的频率范围。这种方法最初被应用到模拟数据的牛顿流体中的陷阱各向异性引起的粘度的最大误差从~ 150%降低到小于6%。该方法的有效性得到证实的实验MOT测量与水和明胶溶液进行，从而证实了流体的微观流变学可以可靠地提取在一个很宽的频率范围内，在任何任意方向。这项工作打开了一扇大门，完全spatiallyandangularly解决三维映射的流变特性的软材料在一个广泛的频率范围。
Microrheology with optical tweezers (MOT) is an all-optical technique that allows the user to investigate a materials’ viscoelastic properties at microscopic scales, and is particularly useful for those materials that feature complex microstructures, such as biological samples. MOT is increasingly being employed alongside 3D imaging systems and particle tracking methods to generate maps showing not only how properties may vary between different points in a sample but also how at a single point the viscoelastic properties may vary with direction. However, due to the diffraction limited shape of focussed beams, optical traps are inherently anisotropic in 3D. This can result in a significant overestimation of the fluids’ viscosity in certain directions. As such, the rheological properties can only be accurately probed along directions parallel or perpendicular to the axis of trap beam propagation. In this work, a new analytical method is demonstrated to overcome this potential artefact. This is achieved by performing principal component analysis on 3D MOT data to characterise the trap, and then identify the frequency range over which trap anisotropy influences the data. This approach is initially applied to simulated data for a Newtonian fluid where the trap anisotropy induced maximum error in viscosity is reduced from ~ 150% to less than 6%. The effectiveness of the method is corroborated by experimental MOT measurements performed with water and gelatine solutions, thus confirming that the microrheology of a fluid can be extracted reliably across a wide frequency range and in any arbitrary direction. This work opens the door to fully spatiallyandangularly resolved 3D mapping of the rheological properties of soft materials over a broad frequency range.