Low-Cost Laser Micromachining Super Hydrophilic-Super Hydrophobic Microgrooves for Robotic Capillary Micromanipulation of Microfibers.

Bo Chang,Yuhang Feng,Quan Zhou,Jialong Jin

doi:10.3390/mi12080854

Bo Chang, Yuhang Feng + Show 2 more

Open Access

https://doi.org/10.3390/mi12080854

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Abstract

Capillary self-alignment technique can achieve highly accurate and fast alignment of micro components. Capillary self-alignment technique relies on the confinement of liquid droplets at receptor sites where hydrophobic–hydrophilic patterns are widely used. This paper reports a low-cost microsecond pulse laser micromachining method for fabrication of super hydrophilic–super hydrophobic grooves as receptor sites for capillary self-alignment of microfibers. We investigated the influence of major manufacturing parameters on groove sizes and wetting properties. The effects of the width (20 µm–100 µm) and depth (8 µm–36 µm) of the groove on the volume of water droplet contained inside the groove were also investigated. We show that by altering scanning speed, using a de-focused laser beam, we can modify the wetting properties of the microgrooves from 10° to 120° in terms of the contact angle. We demonstrated that different types of microfibers including natural and artificial microfibers can self-align to the size matching super hydrophilic–super hydrophobic microgrooves. The results show that super hydrophilic–super hydrophobic microgrooves have great potential in microfiber micromanipulation applications such as natural microfiber categorization, fiber-based microsensor construction, and fiber-enforced material development.

Highlights

Minimization of surface energy is the fundamental principle behind capillary self-alignment, where the gradient of the surface energy drives the micro components towards target receptors [5,6,7]
The results show that it is preferable for the groove to be super hydrophilic, so that the groove can be completely wetted by water droplets for microfiber capillary self-alignment
This paper reports a simple and low-cost laser micromachining method for fabrication of super hydrophilic–super hydrophobic grooves for capillary self-alignment of microfibers

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The droplet confinement has been demonstrated using a hydrophilic receptor on hydrophobic background [8], on superhydrophobic background [9,10], an oleophilic receptor on oleophobic background [11], and topological protruding receptor [12,13,14] These receptor sites are usually fabricated using lithography technology, which can reach high manufacturing accuracy but is often costly and requires a cleanroom environment. We study the influences of fabrication parameters of the grooved surfaces on capillary self-alignment of microfibers, and we show that by altering scanning speed using a de-focused laser beam, we can modify the wetting properties of the microusing a de-focused we can modify theangle.

Laser Micromachining of Super Hydrophilic–Super Hydrophobic Grooves

Robotic System for Capillary Self-Alignment of Microfibers

Criterion for Droplet Confinement

Influence

Conclusions