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Delivery and actuation of colloidal microbots in three dimensional microenvironments for biomedical applications
Zimmermann, Coy
Zimmermann, Coy
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2023
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Abstract
Microbots are an exciting emerging biomedical technology where micro-scale "bots" controlled
through external fields could potentially perform feats like precise remote surgery, targeted drug delivery,
and fine mechanical work. One such rolling microbot design uses commercially available colloidal
superparamagnetic beads which assemble in situ under an external rotating magnetic field into disk
shaped "microwheels". This thesis further develops a technology that could have broad biomedical
implications for enhancing modern drug delivery technology in challenging microenvironments.
First, we show that microwheels can travel up extreme inclines (80°), demonstrating that only a small
load force is required to sustain rolling. At high concentrations, microwheels exhibit swarming modes
which can be modified with specific magnetic field patterns. These modes enable unique functionality
like fast velocity, high climbing rates, broad deposition, and local mechanical action to aid in drug
delivery.
Second, we show that individual microwheel building blocks can be aerosolized into droplets which
can travel through the air and then reassemble after landing on another surface. These reassembled
microwheel swarms can enhance delivery by driving deeper into 3D printed lung models or can be
specifically directed to target a chosen pulmonary branch.
Third, by using both magnetic force and torque, we show that microwheels can move on all surfaces
regardless of their orientation. Since microwheels roll with simple rotating fields and very little load
force, the required fields can be generated by a single rotating permanent magnet with three degrees of
freedom. This simple technique enables swarm targeting in complex 3D capillary network models.
Fourth, an original open source microbot tracking software package is detailed that allows high
throughput analysis of microscopy video. With this, large datasets can be extracted easily from
multivariable experimental arrays. Additionally, individual microbots can be studied in detail using the
trajectory inspector tool.
Together, the work presented in this thesis is a substantial step towards understanding and using this
transformative microbot technology in a clinical setting. These novel techniques enable microbot
movement in the complex 3D microenvironments in the body, including the pulmonary, gastrointestinal,
and vascular systems.
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