Fully automated 3D assembly of nanoparticle building blocks using optical tweezers

Advances in 3D nanofabrication can enable photonic materials and devices that are currently infeasible, including photonic metamaterials, ultra-compact imaging devices, and biosensors. Here we present the 3D assembly of hundreds of nanoscale building blocks using optical positioning and linking (OPAL), which is based on optical tweezers and biotin-avidin chemical linking. A microfluidic chip is used to deliver different building blocks to different loading zones surrounding an assembly zone. A quadrant photodiode signal processed using principal component analysis provides feedback for automatic loading of the optical trap. A computer-controlled translation stage precisely places each building block according to a predefined set of coordinates. We use a combination of the discrete dipole approximation, finite difference time domain, and finite element methods to design arrangements of particles for different applications, including metasurface design, 3D magnetic metamaterial design, and nanostructured microtoroidal optical resonator sensors for toxic gases.