An experimental design for the control and assembly of magnetic microwheels

Abstract

Superparamagnetic colloidal particles can be reversibly assembled into wheel-like structures called microwheels (µwheels) which roll on surfaces due to friction and can be driven at usercontrolled speeds and directions using rotating magnetic fields. Here, we describe the hardware and software to create and control the magnetic fields that assemble and direct µwheel motion and the optics to visualize them. Motivated by portability, adaptability and low-cost, an extruded aluminum heat dissipating frame incorporating open optics and audio speaker coils outfitted with high magnetic permeability cores was constructed. Open-source software was developed to define the magnitude, frequency, and orientation of the magnetic field, allowing for real time joystick control of µwheels through two-dimensional (2D) and three-dimensional (3D) fluidic environments. With this combination of hardware and software, µwheels translate at speeds up to 50 µm/s through sample sizes up to 5 cm x 5 cm x 5 cm using 0.75-2.5 mT magnetic fields with rotation frequencies of 5-40 Hz. Heat dissipation by aluminum coil clamps maintained sample temperatures within 3 ˚C of ambient temperature, a range conducive for biological applications.With this design, µwheels can be manipulated and imaged in 2D and 3D networks at length scales of micrometers to centimeters.

Multimodal microwheel swarms for targeting in three-dimensional networks

“…To achieve this, a custom-built 3D printed microscope and actuation system was fabricated (Fig. 6 ) where coils supply the rotating magnetic fields in tandem with established signal generation software 47 . The z axis consists of two 50 mm i.d.…”

“…Additional 0.2% SDS solution was added to fill up each sample chamber before closing. A standard rotating magnetic field was used for all experiments with a field strength of 3.7 mT, 40 Hz, and 30° camber angle 47 . All µwheel tracking was performed using custom particle tracking software MuTracker with the complete source available on GitHub 48 – 51 .…”

Removing plasmin from the equation – Something to chew on…

“…These µwheels can be loaded with therapeutic agents that are delivered to the site of thrombosis. 46 The µwheels platform is being developed to co-deliver tPA and plasminogen to overcome several limitations of current thrombolytic therapies, including plasminogen consumption. 46,47 Targeting of inhibitors of fibrinolysis has been considered as an alternative to thrombolytics to promote fibrin degradation by enhancing endogenous plasmin generation or activity.…”

“…Alternative thrombolytic delivery systems include microwheels (µwheels), which use superparamagnetic colloidal beads and magnetic fields to roll along surfaces at high velocity. These µwheels can be loaded with therapeutic agents that are delivered to the site of thrombosis 46 . The µwheels platform is being developed to co‐deliver tPA and plasminogen to overcome several limitations of current thrombolytic therapies, including plasminogen consumption 46,47 …”

“…These µwheels can be loaded with therapeutic agents that are delivered to the site of thrombosis 46 . The µwheels platform is being developed to co‐deliver tPA and plasminogen to overcome several limitations of current thrombolytic therapies, including plasminogen consumption 46,47 …”