Tom's scribbles on: Medical Device Prototyping

A view from the front-line trenches of product development.

In this post, we take a look at the necessity of producing prototype builds combining both form and function, at an early stage in the development cycle.

There is a dream situation for an Engineer developing a medical device; a fully detailed and approved functional requirements document lands on their desk, along with a Gantt chart giving plenty of time for solving technical issues and working through design iterations. Steady progress could then be made on the instrument’s function, as a laboratory worth of functionality is squeezed down into a PlayStation sized box. In parallel, a separate team

could be looking at what differentiates the look of that box from a PlayStation, and how on earth they fit the user specified 12” high definition display from the requirements into the box, or indeed the budget.

Unfortunately, end users rarely (never) have a neat list of all the possible requirements, and so rather than this imagined engineering Utopia, technical development tends to start with a reasonably woolly end goal. So, after lots of late nights and pizza, a triumphant team eventually demonstrates successful core functionality, on a fairly utilitarian proof-of-principal rig, held together with so much patched code that only someone with a PhD in software development (or any teenager) can operate. Traditionally we’d call this a ‘works like’ prototype, performing the functions of the final device, but not yet ready for user contact. The partner to this is the ‘looks like’ prototype where a product designer would make an ergonomically beautiful (if a little too small to fit everything in) model ready for user interaction feedback. With the two prototypes built, the form/function wrestling match starts as the two are combined, and the ugly functional duckling becomes, well, an ugly, less functional, but admittedly smaller duckling. But the product is on the road, in many iterations time, to becoming a swan.

However, with timelines and funding runways now shorter than ever before, the reality of any prototype is that often they’ll be in the hand luggage of the CEO and flying halfway around the world within a few hours of it first ‘switching on’, eager to show progress to investors, potential customers, or partners. This means that now, the perfect prototype is one that can be easily mistaken for a marketed product. In particular, medical device prototypes also need to fit the complex, organic shapes encountered when designing for the human body, while being fully functional for testing, and data collection. Additionally, valuable learnings come from watching potential users handle prototypes early in the development cycle; users will always impress you with the novel ways they find to mis-follow your beautifully designed user interface steps.

So, how do we produce the ‘looks like’ enclosure for your ‘works like’ prototype in such a way to minimally impact the time it takes to get useful information out of the prototype? 3D printing immediately comes to mind as an effective way to get the instrument in an enclosure approximating a final form, but other options such as a cast from a silicon mould, or even machining parts can be cost effective and produce a more appropriate end result. Fully understanding the range of rapid prototyping options available during a product's early design stages can lead to satisfying prototype builds, generating valuable feedback for the design team, demonstrating progress, reducing development time and costs, and stimulating potential product enhancements.

There are steps you can take to short cut the journey to a prototype possessing at least a nod towards form. When designing your product’s enclosure try to minimise the number of individual parts required. You will almost always need at least two: a top piece and a bottom piece, but for each additional component used you’re multiplying the time and complexity of the assembly. This is also the time to play dirty: even if you’re advertising a removeable battery in the final product, does it need to demonstrate that now? If not, ditch it. Tape, superglue, sharpie marker, and an incredible amount of manually filing down parts to make everything fit together have all featured heavily in prototypes I’ve built, prototypes which have been successful in helping companies hit funding milestones, been exhibited at trade shows, and even shown on TV. The fear that someone will look closely inside never goes away, but time spent making the final product, or at least the next iteration, is much better spent than time worrying about it too much.

Finally, the nice fringe benefit of having prototypes look like they belong in the hands of a user is no longer having to explain to members of your engineering team why the hacked together Frankenstein rig they’d rushed together is now on a conference stand in Las Vegas, a week after you’d promised their quick work to prove function would stay safely hidden away…

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