ALPS: An Automated Liquid Pipetting System for Spheroid Handling in Nanoliter Droplets

Cell spheroids provide physiologically relevant 3D cell models, but the manual handling of individual spheroids remains challenging, particularly in miniaturized, high-density formats such as droplet microarrays (DMAs). Here, we present ALPS, an automated liquid-handling platform that collects spheroid-containing nanoliter droplets and redeposits them to specified target spots within or between DMAs. Using HEK (human embryonic kidney) spheroids, ALPS achieved transfer yields of up to ~80% under optimized conditions with a processing time of ~5 s per sample. Transferred spheroids retained morphology after handling and showed a ~1.25-fold increase in diameter within 24 h, indicating that the transfer procedure did not compromise spheroid structural integrity. Together, these results establish ALPS as a practical interface between high-density on-DMA spheroid generation and standard downstream formats, including microtiter plates and tube racks, enabling scalable 3D culture workflows.