This presentation will describe the use of analytical models and physical measurements to characterize the tribological behaviour of pen injectors for self-administration of biopharmaceuticals. One of the main performance attributes of this kind of device is its efficiency in transmitting the external force applied by the user on to the cartridge inside the pen in order to effectuate the injection. This injection force efficiency characteristic is determined on the one hand by the mechanical design of the pen and on the other by the frictional properties of the materials employed. The focus here is on the development of new devices and, in this context, using tribological data to select the best materials for a given mechanical design. The work encompasses the development of simple analytical models to describe the relationship between part geometry, coefficient of friction and force transmission as well as the definition of a test set-up for measuring the relevant tribological properties. The models are used to benchmark existing device designs and determine the relative influence on overall efficiency of different part interfaces in a given design. The data generated with the test set-up allows the evaluation of the performance of an interface in terms of absolute friction level, as well as in terms of variability in friction both during an injection cycle and between cycles. The approach is used to assess different types of base polymers, a range of given base polymers with different types of additives and masterbatches, as well as the influence of external lubrification. The results show that the material has a significant impact on frictional properties, and that the performance varies as much between versions of a given base polymer with different additives as between different base polymers. It is also found that external lubrification does not always improve performance.

Development of devices for self-injection: Using tribological analysis to optimize injection force

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.