Abstract
Wireless actuation at the nanoscale is vital in many contexts, and magnetic fields acting on nanoparticles (NPs) are among the most effective tools when actuation concerns linear forces. However, effective tools to apply torques at the nanoscale are still missing, because NPs where the magnetic moment is strongly coupled to the lattice agglomerate due to their high magnetic moment. Here, we show that gallium-doped ε-iron oxide NPs have small interparticle magnetic interactions and huge lattice-coupling for efficiently applying torques at the nanoscale. In this view, they are expected to be useful tools to efficiently apply mechanical forces to induce cellular apoptosis and to discern between mechanical and thermal contributions to cellular apoptosis currently under debate.
Highlights
Wireless actuation at the nanoscale is vital in many contexts, and magnetic fields acting on nanoparticles (NPs) are among the most effective tools when actuation concerns linear forces
In the NPs explored so far, this high coercivity is generally associated with a high magnetization, which is of interest for applications such as magnetic recording but not that much for biomedical applications and wireless actuation at the nanoscale, due to the propensity of these NPs to aggregate by magnetic dipolar interactions[9] a full exploitation of the exciting possibilities offered by mechanical magnetic actuation calls for NPs with both high coercivity and low magnetization
We show that this unique combination can be achieved by gallium-substituted e-iron oxide NPs, where strong magnetic-lattice coupling of the e-iron oxide phase grants a high coercivity and gallium doping the tuning of saturation magnetization
Summary
The intrinsic coercivity of the e-Ga0.46Fe1.54O3 is still quite high (Hc = 621 kA mÀ1, Fig. 1) whereas the saturation magnetization is still low (MS = 28.5 Am2 kgÀ1) enabling torque actuations while avoiding aggregation by dipolar magnetic interactions, opening the way for a torque-driven mechanical and mechano-thermal wireless actuation on individual NPs, as discussed below.
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