从位移到角度：基于钻石的3D旋转传感用于高精度细胞力测量
From Displacement to Angle: Diamond-Based 3D Rotation Sensing for High-Precision Cellular Force Measurement
AI总结：
本文提出基于钻石的3D旋转传感方法，通过直接测量角度来高精度测量细胞力，克服传统位移测量的限制。
摘要：
细胞牵引力通常通过追踪珠子或微柱的位移来测量，这种方法受到光学衍射和经典欧拉-伯努利梁假设的限制，仅在微柱的长宽比较大且牵引引起的变形相对小时准确。本文提出了一种替代方法：通过直接测量微柱的旋转角度来量化力，同时使用荧光纳米钻石作为嵌入的3D方向标记。具体来说，通过将光学检测磁共振（ODMR）与激光偏振调制（LPM）相结合，我们能够以亚度精度（约0.5度）确定附着在PDMS微柱上的纳米钻石的完整三维方向。这种基于角度的测量框架绕过了位移跟踪的分辨率限制，并且在粗壮梁或大变形情况下仍然有效。有限元模拟显示，与传统位移方法相比，我们的方法至少将力估计误差减少了10%。此外，我们成功捕捉了微柱的多维变形——包括弯曲和扭转——这些变形无法通过传统位移方法获取。总之，我们的工作建立了基于钻石的角力显微镜作为机械生物学的高精度平台。
英文摘要：
Cellular traction forces are conventionally measured by tracking the displacement of beads or micropillars, an approach fundamentally limited by optical diffraction and the classical Euler-Bernoulli beam assumption, which is accurate only when the traction-induced deformation is relatively small while the aspect ratio of micropillars is large. Here we introduce an alternative approach: quantifying force through direct measurement of rotational angle, in addition of displacement of the micropillar, using fluorescent nanodiamonds as embedded 3D orientation markers. Specifically, by integrating optically detected magnetic resonance (ODMR) with laser polarization modulation (LPM), we determine the complete three-dimensional orientation of nanodiamonds attached to PDMS micropillars with sub-degree precision ($\sim$0.5$^\circ$). This angle-based measurement framework bypasses the resolution constraints of displacement tracking and remains valid for stocky beams or when large deformations occur. Finite-element simulations demonstrate that our method reduces force estimation errors by at least 10% compared to conventional displacement-based approaches. Moreover, we successfully capture multidimensional pillar deformations -- including bending and twisting -- that are inaccessible to conventional displacement-only method. Taken together, our work establishes diamond-based angular force microscopy as a high-precision platform for mechanobiology.
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