Fabrication of 2D nanoslits for nanofluidic devices via local laser heating based on the fiber fuse phenomenon

Abstract We propose a novel two-dimensional (2D) nanoslit forming method for silica glasses. Continuous-wave (CW) laser-induced modified lines caused a stress distribution that contributed to 2D nanoslit formation between the modified lines. The processed 2D nanoslit exhibited a wedge-shaped clearance profile, opening at the glass surface, gradually narrowing, and closing inside. The nanoslit interior had a smooth surface, and the arithmetic average roughness (Ra) measured in a limited region was 6 nm. In the case where the laser power was 30 W, the length was ~ 2.2 mm, the width was ~ 170 μm, and the maximum clearance was ~ 300 nm. Polarization camera observations revealed the formation mechanism. The modified line was divided into parts with and without voids. The presence and absence of voids resulted in different circumferential stress states. A modified line without voids provided tensile stress, which contributed to crack propagation. A modified line with voids provided compressive stress, which contributed to crack arrest. Therefore, our approach allows the formation of internal stress at arbitrary positions within glass and facilitates the shape design of 2D nanoslits. The flow of acetone into the 2D nanoslit was demonstrated, indicating that the nanoslit can be used as a nanoflow channel.