Low-cost laser micromachining super hydrophilic-super hydrophobic microgrooves for robotic capillary micromanipulation of microfibers

Funding Information: Funding: This research was funded by the National Natural Science Foundation of China (grant no. 61703255) and the Academy of Finland (Grant No. 296250). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.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.Peer reviewe