Real-time in-die compaction monitoring of dry-coated tablets

The practicability of a pulse–echo ultrasonic approach developed for the real-time quality monitoring of dry-coated tablets in the tablet press during compaction is evaluated. The punch–tablet interface (i.e., steel–tablet) is the boundary condition that dictates the viability of acoustic in-die compaction monitoring. The current study utilizes compacted tablets with a simulated punch–tablet interface to achieve the required waveform detectability levels needed for in-die compaction monitoring. The geometric and mechanical properties of a dry-coated tablet are crucial to its structural functions and therapeutic effectiveness, therefore they are monitored especially when the control of dissolution rates of their active ingredients are critically important. Acquired pulse–echo ultrasonic waveforms in the tablet could provide the time-of-flight information needed to determine the thickness, elasticity and/or integrity of the relevant layer, and bonding quality between layers depending on the given parameters. Since the amplitudes of the reflected waves are extremely low due to the high acoustic impedance mismatches of tablet materials and die/punch materials, signal processing techniques are required to extract the wave arrival times. In current study, it is demonstrated that the reflection of an ultrasonic pulse generated by a transducer embedded in a die or a punch from the coat–core interface can be acquired by the same transducer.

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