Small-molecule organic ice microfibers.

Small organic molecules are essential building blocks of our universe, from cosmic dust to planetary surfaces to life. Compared to their well-known gaseous and liquid forms that have been extensively studied, small organic molecules in the form of ice at low temperatures receive much less attention. Here, we show that supercooled small-molecule droplets can be drawn into highly uniform amorphous ice microfibers with lengths up to 5 cm and diameters down to 200 nm. In the experimental test, these fiber-like ices manifest excellent mechanical flexibilities with elastic strain up to 3.3%. Meanwhile, they can guide light with loss down to 0.025 dB/cm that approaches the material absorption limit and offer high optical nonlinearity for low-threshold supercontinuum generation. Notable temperature-dependent Young's modulus and icing-induced refractive-index increase are also found. These results may open a promising category of low-temperature materials for both scientific research and technological applications.