3D-printed reconfigurable magnetic soft millirobots for intelligent digital microfluidics

Magnetic digital microfluidics (MDM) offers an attractive approach to miniaturised in vitro diagnostics, but most conventional platforms remain limited to predefined, planar droplet handling without the ability to rectify operation failures. Here, we present an intelligent MDM platform in which magnetic soft millirobots (MSMRs) function as reconfigurable robotic end-effectors for 3D droplet manipulation under closed-loop control based on 2D visual detection and height-dependent perspective correction. A magnetic pick-and-place mechanism exchanges a 3D-printed MSMR gripper and pipettor on demand. These MSMRs transport, merge, dispense, and split droplets, as well as collect and resuspend bacterial colonies in an oil-immersed workspace. The MSMR gripper captured 10–30 μL droplets with a success rate above 95%, and the MSMR pipettor dispensed 5.19 μL droplets with a coefficient of variation of 2.1%. Both tools retained their droplet-handling function after 10 000 reversible actuation cycles. The computer vision module enables real-time recognition and tracking, spatial calibration, operation verification, failure rectification, and result interpretation. With samples, reagents, and protocols preloaded, the platform autonomously completed the Carba NP assay for detecting carbapenemase-producing Enterobacteriaceae. These results establish MSMRs as a promising strategy for adaptive, failure-aware MDM platforms for diagnostic automation.