Directional Micro-Grooved Fibers with Theoretical Infinite-Length Toward Liquid Self-Transport
Micro-structured surfaces have attracted increasing attention due to their great potential applications. However, it is still a challenge to continuously fabricate micro-structured surfaces based on thermoplastics by a facile, low-cost, and environmentally-friendly method. Herein, with the help of the extrusion molding method and an elaborately designed mold, micro-grooved fiber (MGF) based on high-density polyethylene (HDPE) is continuously prepared. Theoretically, infinitely long MGFs with feature sizes down to a few microns can be efficiently fabricated because of the continuous fabrication characteristic of the melt extrusion method. Interestingly, left- and right-handed micro-grooves with different helix angles can be produced by applying twisting at the die exit, and the macroscopically MGF springs can be further fabricated via a self-designed three-dimensional helical enwind device. By regulating wettability, MGF can achieve liquid self-transport on predefined paths. In addition, MGF fabric exhibits rapid evaporation behavior, whose evaporation rate is about 4 times higher than that of the Smooth fiber (SMF) fabric and 2 times higher than that of the most popular commercial quick-drying fabric (i.e., Cool-max fabric). This work proposes a facile and environmentally-friendly method for continuously preparing low-cost and flexible MGF, opening a new pathway to develop fiber-based microfluidic systems following the concept of "functionalized processing for thermoplastics".