Genentech Injection Device Simulator: Inventing a new…

Genentech, the renowned biotechnology company, needed a research tool to help in the characterisation of drug containment approaches. A machine that could simulate the effects of an auto-injector would enable Genentech to test and prototype devices without actually building them, saving a great deal of effort and resources in the process.

During a lunch break we had with Genentech team members for a different project, they expressed frustration at their inability to find a firm that would build the tool they wanted. Every firm Genentech approached said it wouldn’t be possible to build the motion control system such a device would require. Intrigued, we started doing calculations to determine if it truly was impossible. By the end of lunch, the mathematical proof was on the whiteboard…

An auto-injection device allows patients to inject themselves with medicine by triggering a spring-and-cartridge mechanism. These auto-injectors can be incredibly fast and forceful, so the simulator needed to be powerful enough to replicate the speed and force of an actual injection device’s spring. It also had to be precise and completely controlled, regardless of variations in drug and delivery method.

Typically, motion control systems operate with a position versus time control loop, where the object in motion is expected to be in a certain position at any given time. However, due to the way auto-injectors are constructed, time is an unknown factor.

Therefore, the simulator needed to be built with a force versus position control loop, which calculates trajectory with force as a function of position, velocity, and acceleration. Since we had calculated that this control loop should be mathematically possible, we knew that we could determine the physics needed to make it work. After building a small prototype to test the control loop in practice, we started to build a full-scale simulator with this unconventional motion control system.

To deliver the necessary force, we built a high-performance linear motor capable of up to 50g of acceleration, enabling researchers to replicate the extreme speed and force of some auto-injectors. The main shaft is mounted on a rotating arm and can be completely inverted, enabling researchers to accurately simulate injections that are administered from above or below the injection site.

We ensured that the quality and construction of the design met our high standards, and we are proud to have built the only device of this type in existence. Able to perfectly execute any specified trajectory, the injection device simulator has completely transformed how Genentech develops new auto-injectors. The ability to determine required parameters prior to building a new device has saved Genentech a great deal of time and money.