A reconfigurable 'lab-in-the-air' platform for three-dimensional digital microfluidics via dynamically actuated liquid marbles

Conventional digital microfluidics is confined to two-dimensional electrode arrays, limiting its ability to manipulate droplets along arbitrary paths in three-dimensional (3D) space, which is a capability crucial for emulating complex biological interactions or performing flexible chemical synthesis. Here, we transcend this planar paradigm by introducing a reconfigurable 'lab-in-the-air' platform. This platform achieves software-defined, full 3D manipulation of individual droplets by employing liquid marbles (LMs) as stable, encapsulated carriers and actuating them via programmable DC dielectrophoresis using a set of adjustable suspended electrodes. The system reliably executes the complete sequence of pick-up, precision translation, and gentle release of 5-30 μL LMs in open space under 2 kV DC actuation, overcoming the adhesion forces that typically hinder droplet deposition. Integrated computer vision enables closed-loop, intelligent control for autonomous operations. We demonstrate the platform's versatility by programming complex 3D trajectories and executing a multi-step droplet fusion reaction at an arbitrary location in space. This work establishes a fundamentally new paradigm for microfluidics, shifting from fixed, chip-based architectures to a dynamic, airborne laboratory that can be virtually reconfigured on demand for advanced bioassays and chemical processing.