Nanomagnets

(1) Magnetic alignment and actuation: In the magnetic-alignment and actuation component of the program, we have set up a system for stacking patterned membranes. The system brings the membranes into coarse alignment before the nanomagnet arrays bring the membranes into fine alignment.

Nanomagnets have proven to be very effective to actuate and align nanostructured membrane.

In this alignment scheme, the matching nanomagnet arrays on the substrate and the membrane attract and distort the membrane into alignment. Two forms of compliant membranes, patterned flexures or ultra-compliant polymer membranes, are being explored so that the nanomagnet forces can overcome the elasticity of the membranes.

(2) Actuation for Tunable Optical Metamaterials: Metamaterials are designed structures with sub-wavelength features having constitutive optical properties that do not exist in nature. For instance, they can achieve negative-index refraction and enable optical cloaking.1,2 The MURI program at MIT on nanomembranes is developing methods for fabricating such structures and as well as for their actuation. The actuation concept consists of patterning periodic sub-wavelength structures on top of a freestanding grating with embedded nanomagnets. By applying a perpendicular magnetic field, the grating lines attract each other and distort the pattern to a designed structure that behaves, for example, like a GRIN lens. Experimentally, silicon nitride gratings with embedded nanomagnets have been fabricated and successfully actuated using this method and tested as regular diffraction gratings for validation purposes.3,4 We also show the shift of the first diffraction order under normal illumination by a laser beam showing chirp due to compressive deformation the grating.