Alignment and orderly distribution of microfibers have a major effect on the mechanical, electrical, and thermal properties of the fiber reinforced materials, biomimetic materials, and soft microsensors. However, it is still a challenging task to precisely align and distribute microfibers and construct complex patterns. This paper proposes a surface tension-based method to align and orderly distribute microfibers. A model was developed to simulate the surface tension driven alignment of the microfiber. We designed and fabricated hydrophilic–superhydrophobic grooved surfaces. We demonstrated that the microfibers can self-align to the hydrophilic–superhydrophobic grooves with different geometries. We studied the influence of the volume of the droplet and bias on the alignment success rate. The results indicate that the process can tolerate large variations of the bias and the volume, unless the volume is not enough to cover the groove. We further investigated the influence of the width of the groove on the alignment accuracy. The results show that the alignment accuracy is largely depending on the size difference between the groove and the microfiber; the better the size of the groove matches the size of the fiber, the higher the alignment accuracy will be achieved. The proposed method has great potential in construction of complex microstructures using microfibers.
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.
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