Utilizing Iron's Attractive Chemical and Magnetic Properties in Microrocket Design, Extended Motion, and Unique Performance

Abstract

All‐in‐one material for microrocket propulsion featuring acid‐based bubble generation and magnetic guidance is presented. Electrochemically deposited iron serves as both a propellant, toward highly efficient self‐propulsion in acidic environments, and as a magnetic component enabling complete motion control. The new microrockets display longer lifetime and higher propulsion efficiency compared to previously reported active metal zinc‐based microrockets due to the chemical properties of iron and the unique structure of the microrockets. These iron‐based microrockets also demonstrate unique and attractive cargo towing and autonomous release capabilities. The latter is realized upon loss of the magnetic properties due to acid‐driven iron dissolution. More interestingly, these bubble‐propelled microrockets assemble via magnetic interactions into a variety of complex configurations and train structures, which enrich the behavior of micromachines. Modeling of the magnetic forces during the microrocket assembly and cargo capture confirms these unique experimentally observed assembly and cargo‐towing behaviors. These findings provide a new concept of blending propellant and magnetic components into one, toward simplifying the design and fabrication of artificial micro/nanomachines, realizing new functions and capabilities for a variety of future applications.

Hybrid Nanovehicles: One Machine, Two Engines

“…For instance, the use of dual stimuli offers multiple practical solutions to precisely guide nanomotors through a hybrid trigger. Chemically and physically propelled nanomotors have been integrated with diverse ferromagnetic segments (Ni, Fe, and Co) to establish control over the nanomotor directionality, by aligning them with a magnetic field or via magnetic torque applied to the motor structure . Such magnetic fields can be produced by a magnetic bar which offers direct manipulation or with a Helmholtz coil that produces a highly accurate 3D control.…”

Progress toward Catalytic Micro‐ and Nanomotors for Biomedical and Environmental Applications

“…The Fe‐NP aggregates submerged in an aqueous solution of 3.38 wt% citric acid and 1% SDS moved with a speed of 7–20 µm s −1 . The electrodeposited multilayered PEDOT/Au/Fe‐based micromotors propelled by reaction with 1.2 m HCl to the speed of ≈35 µm s −1 . The chemical reaction involved is represented as Fe(s) + 2H 3 O + → Fe 2+ (aq) + 2H 2 O + H 2 (g).…”

Geometry Design, Principles and Assembly of Micromotors

“…Later, Solovev et al found that an incorporated ferromagnetic layer in rolled-up microtubes can be used to control the motion of microjet engines with magnetic fields [ 137 ]. Subsequently, magnetic control of microjets was improved [ 138 , 139 , 140 ] as well as other NMs including nanowire motors [ 141 ], Janus particles [ 142 , 143 ], paperbots [ 144 ], liquibots [ 145 ], freestyle nanoswimmer [ 146 ], fish-like nanoswimmers [ 147 ], liquid metal motors [ 148 ], flexible and linked superparamagnetic colloidal chains [ 149 ], chemo-magnetic structures [ 150 ], magneto-electric structures [ 151 ], magneto-acoustic structures [ 152 ] and chiral nanomagnets [ 153 ]. Fuel free NMs have advantages in biomedical applications, since there are no reaction products produced during the navigation [ 154 ].…”