The present invention generally relates to microfluidics, and to spray drying and other drying techniques. Various embodiments of the invention are generally directed to systems and methods for drying fluids contained within a channel such as a microfluidic channel. For example, a fluid may be partially or completely dried within a microfluidic channel, prior to being sprayed into a collection region. In some embodiments, the fluids may be dried relatively rapidly, resulting in spray-dried particles that are partially or completely amorphous. For instance, the fluid may contain salts, drugs, small molecules, ceramics, inorganic species, metals, sugars, polymers, etc., which may be dried to form partially or completely amorphous nanoparticles containing these species.