Rapid mechanical stimulation of inner-ear hair cells by photonic pressure

Hair cells, the receptors of the inner ear, detect sounds by transducing mechanical vibrations into electrical signals. From the top surface of each hair cell protrudes a mechanical antenna, the hair bundle, which the cell uses to detect and amplify auditory stimuli, thus sharpening frequency selectivity and providing a broad dynamic range. Current methods for mechanically stimulating hair bundles are too slow to encompass the frequency range of mammalian hearing and are plagued by inconsistencies. To overcome these challenges, we have developed a method to move individual hair bundles with photonic force. This technique uses an optical fiber whose tip is tapered to a diameter of a few micrometers and endowed with a ball lens to minimize divergence of the light beam. Here we describe the fabrication, characterization, and application of this optical system and demonstrate the rapid application of photonic force to vestibular and cochlear hair cells.作为内耳感受器的毛细胞，可通过将机械振动转换为电信号来感知声音。每个毛细胞的顶表面伸出一根机械天线——毛束（hair bundle），细胞借此感知并放大听觉刺激，从而提升频率选择性并实现宽动态范围。当前用于机械刺激毛束的方法，速度过慢无法覆盖哺乳动物听觉的频率范围，且存在一致性不佳的问题。为克服上述局限，我们开发了一种利用光子力（photonic force）操控单根毛束的方法。该技术采用一根光纤，其尖端被拉锥至数微米直径，并加装球透镜以最小化光束发散。本文详述了该光学系统的制备、表征与应用，并展示了光子力快速应用于前庭（vestibular）与耳蜗（cochlear）毛细胞的实验效果。