Optomagnetically Controlled Microparticles Manufactured with Glancing Angle Deposition

Abstract

Optical trapping and magnetic trapping are common micromanipulation techniques for controlling colloids including micro- and nanoparticles. Combining these two manipulation strategies allows a larger range of applied forces and decoupled control of rotation and translation; each of which are beneficial properties for many applications including force spectroscopy and advanced manufacturing. However, optical trapping and magnetic trapping have conflicting material requirements inhibiting the combination of these methodologies. In this paper, anisotropic microscaled particles capable of being simultaneously controlled by optical and magnetic trapping are synthesized using a glancing angle deposition (GLAD) technique. The anisotropic alignment of dielectric and ferromagnetic materials limits the optical scattering from the metallic components which typically prevents stable optical trapping in three dimensions. Compared to the current state of the art, the benefits of this approach are twofold. First, the composite structure allows larger volumes of ferromagnetic material so that larger magnetic moments may be applied without inhibiting the stability of optical trapping. Second, the robustness of the synthesis process is greatly improved. The dual optical and magnetic functionality of the synthesized colloids is demonstrated by simultaneously optically translating and magnetically rotating a magnetic GLAD particle using a custom designed optomagnetic trapping system. Anisotropic particles are synthesized that are capable of simultaneous optical and magnetic trapping. These micromanipulation techniques are typically exclusive of one another due to material incompatibilities in which ferromagnetic material will lead to excessive optical scattering. The synthesis process described allows the placement of magnetic material such that optically induced instabilities are prevented, creating optically and magnetically functional particles.