High Internal Phase Emulsions Gel Ink for Direct-Ink-Writing 3D Printing of Liquid Metal

3D printing of liquid metal remains a big challenge due to its low viscosity and large surface tension. In this study, we use Carbopol hydrogel and liquid gallium-indium alloy to prepare a liquid metal high internal phase emulsion gel ink, which can be used for direct-ink-writing 3D printing. The high volume fraction (up to 82.5%) of the liquid metal dispersed phase gives the ink excellent elastic properties, while the Carbopol hydrogel, as the continuous phase, provides lubrication for the liquid metal droplets, ensuring smooth flow of the ink during shear extrusion. These enable high-resolution and shape-stable 3D printing of three-dimensional structures. Moreover, the liquid metal droplets exhibit an electrocapillary phenomenon in the Carbopol hydrogel, which allows for demulsification by an electric field and enables electrical connectivity between droplets. We have also achieved the printing of ink on flexible, non-planar structures, and demonstrated the potential for alternating printing with various materials.

液态金属3D打印仍受限于其低黏度与高表面张力的特性，面临巨大挑战。本研究采用卡波姆（Carbopol）水凝胶与液态镓铟合金，制备出可用于直写式（direct-ink-writing）3D打印的液态金属高内相乳液凝胶油墨。分散相液态金属的高体积分数（最高可达82.5%）赋予该油墨优异的弹性性能；而作为连续相的卡波姆水凝胶，则为液态金属液滴提供润滑，确保油墨在剪切挤出过程中流畅流动。上述特性可实现高精度且形状稳定的三维结构3D打印。此外，液态金属液滴在卡波姆水凝胶中表现出电毛细现象，可通过电场实现破乳，并使液滴间形成电连通性。本研究还实现了在柔性非平面结构上的油墨打印，并验证了多材料交替打印的应用潜力。