Optical tweezers are a highly versatile tool for exploration of the mesoscopic world, permitting non-contact manipulation of nanoscale objects. However, direct illumination with intense lasers restricts their use with live biological specimens, and limits the types of materials that can be trapped. Here we demonstrate an indirect optical trapping platform which circumvents these limitations by using hydrodynamic forces to exert nanoscale-precision control over aqueous particles, without directly illuminating them. Our concept is based on optically actuated micro-robotics: closed-loop control enables highly localised flow-fields to be sculpted by precisely piloting the motion of optically-trapped micro-rotors. We demonstrate 2D trapping of absorbing particles which cannot be directly optically trapped, stabilise the position and orientation of yeast cells, and demonstrate independent control over multiple objects simultaneously. Our work expands the capabilities of optical tweezers platforms, and represents a new paradigm for manipulation of aqueous mesoscopic systems.

光学镊子是探索介观世界的一种高度通用的工具，允许非接触操作纳米级物体。但是，用强激光直接照射限制了它们在活的生物标本中的使用，并限制了可以捕获的材料类型。在这里，我们演示了一个间接的光学捕获平台，该平台通过使用水动力对水性颗粒施加纳米级精度控制而没有直接照亮它们，从而规避了这些限制。我们的概念基于光致动微型机械手：闭环控制可通过精确控制光陷微动子的运动来雕刻高度局部化的流场。我们展示了无法直接被光学捕获的吸收粒子的二维捕获，稳定酵母细胞的位置和方向，并同时展示出对多个物体的独立控制。我们的工作扩展了光镊平台的功能，并代表了操纵水介观系统的新范例。