A ferrobotic system for automated microfluidic logistics

Abstract

Automated technologies that can perform massively parallelized and sequential fluidic operations at small length scales can resolve major bottlenecks encountered in various fields, including medical diagnostics, -omics, drug development, and chemical/material synthesis. Inspired by the transformational impact of automated guided vehicle systems on manufacturing, warehousing, and distribution industries, we devised a ferrobotic system that uses a network of individually addressable robots, each performing designated micro-/nanofluid manipulation-based tasks in cooperation with other robots toward a shared objective. The underlying robotic mechanism facilitating fluidic operations was realized by addressable electromagnetic actuation of miniature mobile magnets that exert localized magnetic body forces on aqueous droplets filled with biocompatible magnetic nanoparticles. The contactless and high-strength nature of the actuation mechanism inherently renders it rapid (~10 centimeters/second), repeatable (>10,000 cycles), and robust (>24 hours). The robustness and individual addressability of ferrobots provide a foundation for the deployment of a network of ferrobots to carry out cross-collaborative logistics efficiently. These traits, together with the reconfigurability of the system, were exploited to devise and integrate passive/active advanced functional components (e.g., droplet dispensing, generation, filtering, and merging), enabling versatile system-level functionalities. By applying this ferrobotic system within the framework of a microfluidic architecture, the ferrobots were tasked to work cross-collaboratively toward the quantification of active matrix metallopeptidases (a biomarker for cancer malignancy and inflammation) in human plasma, where various functionalities converged to achieve a fully automated assay.

Reconfigurable multifunctional ferrofluid droplet robots

“…Ferrofluid droplets form when oil-based (or water-based) ferrofluids are mixed with waterbased (or oil-based) solutions, due to the immiscibility and surface tension. Particularly, oil-based ferrofluid droplets are promising for lab-on-a-chip (28) and bioengineering (21,22) applications, because water-based fluids widely exist in microfluidic channels and the human body, including blood and other biological fluids (20).…”

“…By controlling the applied currents in the electromagnet array or the rigid-body rotational and translational motion of a permanent magnet, the magnetic potential energy well can be shifted across the workspace, enabling the navigation ability of an FDR. For actuation by electromagnets, unlike recent works where only independent electromagnets ("single-coil" mode) are used to actuate ferrofluid droplets each time (28,30), here, we simultaneously control two neighboring electromagnets ("double-coil" mode) to allow an FDR achieving both body elongation and navigation in narrow spaces.…”

“…Fundamental studies have provided striking insights into the physics of ferrofluid droplets at the micro and macro scales (23)(24)(25). Recent works have also demonstrated utilizing these magnetic droplets for engineering applications (26)(27)(28)(29)(30). For example, magnetically actuated droplets have been controlled to navigate on various terrains by forming self-assembled structures and disassemble into multiple smaller droplets to pass through a narrow gap (26), while the functionality of such collective droplets is simple and their ability to complete cooperative tasks is also restricted by the lack of addressability of individual droplets.…”

“…For example, magnetically actuated droplets have been controlled to navigate on various terrains by forming self-assembled structures and disassemble into multiple smaller droplets to pass through a narrow gap (26), while the functionality of such collective droplets is simple and their ability to complete cooperative tasks is also restricted by the lack of addressability of individual droplets. In addition, other magnetically actuated droplet robots have also been proposed with promising proof-of-concept functionalities, such as transporting liquid samples and mixing chemicals in lab-on-a-chip applications (28,29). Yu et al (28) have proposed to employ ferrofluids as droplet robots for automated sample collection and transportation by controlling the Significance This work proposes reconfigurable multifunctional ferrofluid droplets as soft robots to overcome the limitation of existing magnetically actuated miniature soft robots based on elastomers, i.e., they cannot navigate inside very clustered and constrained spaces and reconfigure their shapes in situ for diverse tasks, due to limited deformability and predesigned shapes.…”

“…In addition, other magnetically actuated droplet robots have also been proposed with promising proof-of-concept functionalities, such as transporting liquid samples and mixing chemicals in lab-on-a-chip applications (28,29). Yu et al (28) have proposed to employ ferrofluids as droplet robots for automated sample collection and transportation by controlling the Significance This work proposes reconfigurable multifunctional ferrofluid droplets as soft robots to overcome the limitation of existing magnetically actuated miniature soft robots based on elastomers, i.e., they cannot navigate inside very clustered and constrained spaces and reconfigure their shapes in situ for diverse tasks, due to limited deformability and predesigned shapes. We propose a fundamental mechanism of controlling reconfigurable large deformation (e.g., splitting) and coordinated motions of multiple ferrofluid droplets by programming external magnetic fields spatiotemporally.…”