Weak mechanical forces acting on molecules are in control of a wide variety of (bio)chemical and physical processes. The spatially inhomogeneous nature of these forces has a profound effect on the structure and mechanics of soft and biological materials. Yet, the lack of methods for probing sub-picoNewton forces at high resolution leaves our understanding of these effects incomplete. Here, we solve this challenge by engineering semiconducting polymers to act as ultraweak force sensors. Combining simulations, chemical synthesis, and single-molecule fluorescence spectroscopy, we demonstrate force sensing in single molecules. We achieve grayscale force detection, at a resolution as low as 300 fN, down to the molecular scale. Our approach opens the way to illuminating and quantifying molecular mechanics with unprecedented resolution.

作用在分子上的弱机械力控制着各种各样的（生物）化学和物理过程。这些力在空间上的不均匀性对软性和生物材料的结构和力学产生了深远的影响。但是，缺乏高分辨率探测亚皮克顿牛顿力的方法，使我们对这些影响的理解不完整。在这里，我们通过工程化半导体聚合物以充当超弱力传感器来解决这一挑战。结合模拟，化学合成和单分子荧光光谱，我们证明了单分子中的力感测。我们实现了低至300 fN的分辨率至分子级的灰度力检测。我们的方法为以前所未有的分辨率阐明和量化分子力学开辟了道路。