A Controllable Galinstan Droplet Gripper Driven by Electrically Induced Interfacial Modulation

Gallium-based liquid metals exhibit attractive properties for precision manipulation, combining high fluidity, superior electrical conductivity, and electrically tunable interfacial behavior. Their deformable liquid interfaces provide a promising route for adaptive contact with irregular, fragile, or soft objects. Conventional rigid fixtures may induce surface microscratches, structural damage, or residual contamination when manipulating precision components, such as glass microspheres or optical elements, limiting their use in high-precision assembly. To address these limitations, we propose a compact flexible gripper system that uses an electrically driven Galinstan droplet as the primary actuating element. By regulating the interface between the droplet and the electrolyte through coupled electrocapillary and electrochemical processes, the liquid metal undergoes controllable deformation, enabling stable gripping, holding, and release. Under reverse voltage, the interfacial state of the droplet recovers, allowing the droplet to retract and release the object without visible residue. Integrated with a compact motion platform, the system enables automated transport of small objects under controlled experimental conditions. The effects of applied voltage, NaOH concentration, electrolyte volume, electrode size, clamp geometry, and Galinstan droplet volume were systematically investigated to evaluate the gripping and release performance. The gripper achieved stable clamping within 0.2-4 s and exhibited a relatively long stable holding duration at a low voltage of approximately 0.15 V. In addition to precision glass microspheres, the gripper successfully transported representative objects with different material properties and geometries, including ceramic spheres, iron spheres, and small fish specimens with characteristic sizes of approximately 2 mm. Load-bearing tests further identified a maximum stable transportable load of 0.4 g for the gripper with a 2.25 mm aperture. This work provides a feasible strategy for electrically controlled and gentle manipulation of small objects, demonstrating the potential of Galinstan droplet grippers in precision assembly and small-scale automated handling.