Trapping in a material world

The ability to manipulate small particles of matter using the forces of light, optical trapping, forms the basis of a number of exciting research areas, spanning fundamental physics, applied chemistry and medicine and biology. Historically, a largely unexplored area has been the influence of the material properties of the particle on the optical forces. By taking a holistic approach in which the properties of the particle are considered alongside those of the light field, the force field on a particle can be optimized, allowing significant increases of the optical forces exerted and even the introduction of new forces, torques, and other physical effects. Here we present an introduction to this newly emerging area, with a focus on high refractive index and antireflection coated particles, nanomaterial particles, including metallic nanoparticles, optically anisotropic particles, and metamaterials. Throughout, we discuss future perspectives that will extend the capabilities and applications of optical trapping and shape future avenues of research in this burgeoning field.