R&D professionals regularly encounter contradictory requirements as a matter of course in almost every innovation program. Increasing the performance of one parameter is directly correlated with a decrease in performance of another important system parameter. These contradictions can become the bane of breakthrough results if they are addressed inadequately or not at all. Researchers often resort to optimizing the system as a useful compromise, using a highly iterative procedure. Optimization is viewed as the means to balanced performance outcomes.
Yet, sometimes the performance compromise can relate to life-critical parameters – a scenario faced by medical device R&D scientists and engineers. In healthcare, novel devices are expected to meet diverse and increasingly stringent requirements where dependability and performance can be life-critical. Medical device companies use a validation plan to define process or product requirements in terms of test criteria, calibration and maintenance requirements, cleanliness requirements, particle count criteria, etc.
But what if the new product has contradictory requirements? For example, a catheter may need high tensile strength for pressure infusion tests, but increased strength causes poor performance on mandatory flex test requirements important to guiding the device through an artery. This contradiction – the device must be strong enough and at the same time flexible – presents a major hurdle to meeting critical validation elements. Optimization is either not possible or would lead to a compromise with unacceptable outcomes.
Instead, contradictions can be resolved using simple tools and without compromise-based design methods. For example, one efficient approach is to satisfy both sides of a contradiction by separating requirements in time or space and then solving for each requirement at different moments of time, or for different parts of the object, or at different sections of its non-linear characteristic.
An important step to resolving contradictions is to reframe the initial problem from the outset. For instance, instead of trying to synthesize an optimal material for the whole catheter, a designer can specify different requirements to different sections of the device. By listing contradictory requirements and indicating to which parts of the object / moments of time / stages of its life cycle they apply, solutions become clear and a pathway forward can be developed. A precise and reframed problem statement is essential for developing solutions using a limited set of separation principles.
In summary, contradictions are sometimes obvious, sometimes hidden barriers that exist within most engineered systems. Taking the time and care to unearth them, understand their nature, isolate/exaggerate specific requirements, and then solve for them – rather than optimizing against them – can spell the difference between average products and breakthrough (even life-saving) innovations.