A hollow droplet generator for polymer shell production

Small, spherical, polymer shells are used as fuel containers in inertial fusion experiments. These shells have traditionally been made by spray drying or more recently using droplet generators. It has proven difficult to control product size and wall thickness for thermosetting materials. In this work we describe a dual orifice droplet generator for making hollow shell preforms. The inner orifice injects bubbles of a desired gas into the polymer solution droplet stream. The stream is agitated using a piezoelectric diaphragm and produces uniformly sized hollow droplets. Shells formed from these hollow preforms have tight distributions of diameter and wall thickness.