Terahertz Radar Observes Powder Dynamics for Pharmaceutical Manufacturing

The optical opaqueness of powders has precluded the observation of powder flow dynamics in processing tubes, with important implications, for example, in the pharmaceutical industry, where nondestructive monitoring during the manufacturing process is essential to ensure the quality of the final product and the effectiveness of the process. Taking advantage of the high penetration of terahertz (THz) electromagnetic waves in powders and its wavelength-to-particle size ratio, we demonstrate that a submillimeter-wave pulse-Doppler radar can overcome the present challenges and characterize powder flow dynamics in pharmaceutical manufacturing processes. Mimicking typical vessel shapes in pharmaceutical operations, we were able to characterize falling powder streams in a tube with a sample volume resolution of a few cubic centimeters and a range resolution of about 5 mm. We successfully monitored particle velocity, particle distribution within the tube, and mass flow rate in real time. This remote sensing method, based on advanced THz electronics, opens up the possibility to study and monitor powder dynamics in a wide range of applications.