Laser-Fabricated, Self-Forming Swimmers With Catalytic Propulsion and Magnetic Navigation

Abstract

We have developed an inexpensive rapid process for creating soft, mm-scale self-forming catalytic swimmers for biomedical and environmental applications. The swimmers contain a catalyst such that when exposed to H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> they self-propel. With the additional incorporation of iron oxide nanoparticles (deposited as ferrofluid), we successfully control the navigation of the swimmers using a magnetic field. Unlike the previous reports of catalytic actuators, which use expensive materials (e.g., platinum) and hard substrates (e.g., titanium), our process makes an exclusive use of techniques, which are scalable, economical, and adaptable for large-volume manufacturing (e.g., roll-to-roll), along with materials that are non-toxic and eco-friendly. The devices are created using a planar design, but upon immersion in an aqueous environment, they fold up to create a 3-D architecture, specifically, a tapered cylinder. Tapering is achieved by a range of ablation levels during fabrication, thus creating a gradient of curvatures along the longitudinal axis of the cylinder for improved propulsion efficiency (compared with cylinders or rods). A maximum swimming speed of 7.2 mm/s was observed at 20% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> .