Key Takeaways & Executive Findings
- •• • Continuous melt extrusion enables fabrication of theoretically infinite-length micro-grooved fibers (MGFs) with feature sizes down to a few microns, overcoming batch-processing limitations of lithography or laser-writing. • • MGF fabric achieves an evaporation rate approximately 4 times higher than smooth fiber (SMF) fabric and 2 times higher than commercial Cool-max fabric, demonstrating superior moisture management for activewear. • • By applying twisting at the die exit, left- and right-handed micro-grooves with tunable helix angles are produced, enabling directional liquid transport on predefined paths. • • The process uses high-density polyethylene (HDPE) and is solvent-free, low-cost, and scalable, aligning with environmentally-friendly manufacturing requirements.
Abstract
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".
1. Introduction
Micro-structured surfaces are pivotal for microfluidics, drag reduction, and tissue engineering, yet existing fabrication methods—lithography, micro-milling, laser-writing, plasma etching—suffer from high cost, complex operation, or discontinuous production. Moreover, these techniques typically produce rigid substrates or elastomeric films with poor weavability, limiting their integration into flexible, three-dimensional textile architectures. Thermoplastics offer a compelling alternative due to their low cost, chemical stability, and melt processability, but achieving continuous, high-throughput micro-grooving on thermoplastic fibers remains an unresolved bottleneck.
This work introduces a melt extrusion method with a specially designed mold to continuously produce micro-grooved fibers (MGFs) from high-density polyethylene (HDPE). The approach not only yields theoretically infinite fiber lengths but also enables chirality control via die-exit twisting, allowing directional liquid transport. The resulting MGF fabric exhibits evaporation rates four times higher than smooth fiber fabrics and twice that of commercial quick-drying textiles, positioning this technique as a scalable, eco-friendly route for functional fiber-based microfluidics.
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Mingfu Qiu, Ying Hao, Bo Lu, Shucheng Li, Guoqiang Zheng, Shanshan Xu, Kun Dai, Chaojun Gao, Liwei Mi, Chuntai Liu, Changyu Shen (2026). Directional Micro-Grooved Fibers with Theoretical Infinite-Length Toward Liquid Self-Transport. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3814-2
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Frequently Asked Questions
What is the maximum achievable groove aspect ratio and how does it affect capillary-driven liquid transport?
The paper reports feature sizes down to a few microns, but does not specify the maximum aspect ratio. However, the evaporation rate enhancement (4x vs. smooth fiber) indicates effective capillary action. For precise aspect ratio limits, further parametric studies are required.
How does the twisting process at the die exit influence the helix angle and what range of angles is attainable?
The paper states that left- and right-handed micro-grooves with different helix angles can be produced by twisting at the die exit, but it does not quantify the range. The ability to tune helix angle is critical for directional liquid transport, and the method appears to offer continuous adjustability.
What is the long-term durability of the micro-grooves under repeated mechanical stress (e.g., bending, washing) in textile applications?
The paper does not provide data on mechanical durability or wash fastness. Given the thermoplastic nature of HDPE, the grooves may be susceptible to deformation under stress. Further testing is needed to assess retention of micro-structure and performance after laundering.
How does the cost of this melt extrusion process compare to existing commercial quick-drying fabric manufacturing?
The paper emphasizes low-cost and environmentally-friendly processing, but does not provide a quantitative cost comparison. However, melt extrusion is a mature, high-throughput process, suggesting potential cost advantages over multi-step lithographic or laser-based methods.
Can this method be extended to other thermoplastics beyond HDPE, and what are the limitations?
The paper focuses on HDPE, but the principle of melt extrusion with a designed mold is applicable to other thermoplastics. Limitations may include melt flow properties, thermal stability, and the ability to form precise micro-grooves. Further research is needed to demonstrate generalizability.
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