Arizona State University

New technologies in x-ray free electron lasers (XFEL) have unlocked the ability to study the structures of many important proteins that do not readily form large crystals by enabling “diffraction before destruction” with small crystals. Small crystals also carry reduced complexity, providing diffraction patterns with more detailed features of protein orientation and crystal structure. Consequently, we are developing microfluidic methods to grow and isolate ‘nanocrystals’. We developed a diffusion-based method establishing a gradient of crystallization conditions polling for nanocrystal growth. Many crystallization conditions are probed with one experiment, expediting the process of phase diagram development. Additionally, we have created a microfluidic sorting system driven by size-dependent dielectrophoresis to selectively transport desired crystal sizes into collection chambers. We have demonstrated the functioning principle of this device by experimentally sorting 90 and 900 nm polystyrene beads in excellent agreement with numerical models. In addition, photosystem I crystals were sorted into 100 nm sized fractions, as confirmed by dynamic light scattering and particle tracking measurements.