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  • Writer's pictureKate

Build Safe

When you are focused on learning, building, moving forward and peering into the future, it can be easy to miss the fact that you are doing some potentially dangerous stuff.

Years ago, while working for a blood glucose testing company, I had received several competitor lancets and other bloodletting devices. Eager to test a particularly unique item, I ripped open the sterile packaging, wiped down my arm with alcohol, and fired away. I eagerly inspected the resulting shallow cut, noting the overall shape, depth and the impact of the spring-loaded device while firing. I glanced up to see my coworker staring at me wide-eyed. “Wait…did you just use that on yourself?!” he stammered in disbelief.

Well, yes.

Self-experimentation is a long-established tradition in early medical technology development. The smaller the organization, the fewer the barriers to running the dozens of little “trials” that support the development of a new product. The ultimate freedom belongs to the individual inventor. If I want to walk into a pharmacy, pull a product off the shelf, and try it out, there is no one standing by with forms to fill out first.

This freedom can be dangerous, however. There is often little visual difference between an engineering prototype and a final product, despite a vast difference in risk of harm or injury. As far as I know, I have never experienced an injury due to a fully developed, validated, and properly manufactured medical device. It’s why I had so few compunctions about immediately experimenting with an off the shelf lancet product. That device has been used millions of times, on everything from newborns to geriatric patients.

Have I been injured by prototypes? Many, many times. There was the biopsy device bolted to a lab bench and the unfortunately clumsy coworker that knocked me into it. There were the tiny thermo-electric heaters that self-destructed when the thermocouple was dislodged. There have been burns and abrasions from patch adhesives that were too strong or improperly formulated for skin contact.

What a handful of little scars has taught me is to slow down and think a bit before I (literally) put my own skin in the game. Many products, from cars to baby gear to construction equipment go through an intense risk assessment to identify and mitigate potential dangers from design, manufacturing, misuse. While it would be impossible to do the same for every prototype you build (especially if you are building as quickly and efficiently as you should be), there are some common hazards to look for and keep you, your coworkers, and your test volunteers safe.

Physical Harm

The most obvious kind of harm is physical injury. This can be acute (such as cutting yourself on a sharp edge) or result from long term exposure (such as thermal burns or inhaling dangerous fumes or particles).

Some prototype risk is a direct result of its design or shape. If you are designing a device with needles, blades, or other cutting edges, you should only use a “live” cutting edge when you need to evaluate the cutting performance. If it’s top-heavy, bolt it down. If it moves, put up a shield around it before you turn it on. Wear face shields, gloves and closed toed shoes religiously.

Even if your “device” has all the sharpness and weight of a piece of paper, it can still cause harm. Some of the worst burns I’ve seen were from a poor choice in adhesive. Any material undergoing a chemical reaction (such epoxy curing, paper changing color, or exposure to sunlight) can potentially produce harmful chemicals or an exothermic reaction (see previously mentioned burns).

If you are cutting, grinding, melting, or heating up a material, please ensure proper ventilation. Materials that are safe for skin contact can still be dangerous when inhaled or sprayed into the eyes. Many modern molded plastic parts are composites with fillers and fibers that can be released when cut or ground. This is especially common in high impact polymer cases or boxes, so grab a respirator before you start punching holes in that convenient standard enclosure.

Electrical shock is also a big concern in prototyping. Breadboard components can be easily overloaded, and fuses and grounding strips forgotten. There are many products that rely on high voltage electronics, or simply plug into a household outlet. Do NOT attempt to modify or work on these types of products without the appropriate electrical training or workshop set up.

Damage to Property

While reducing harm to people should be primary, damage to your environment, equipment and tools can also derail your prototyping efforts.

Some of the most critical development testing is downright messy. We purposely test structures to the point of failures so we can be sure they will not do so in regular use in the final product. From my own experience, circulating water baths, angioplasty balloon burst testing, and hemodynamic flow models are all excellent ways to create a very large mess with a very small leak. A former coworker spent an afternoon at the ER after one of the engineers splattered a lab floor with glycerin during a burst test, then went on break before cleaning it up. It led to a bruised hip, several hours of detailed clean-up and (a couple of months later) the complete tear-down and repair of a very expensive automated test stand. Just like kitting yourself out with goggles and gloves, think about PPE (Personnel Protective Equipment) for your workbenches, equipment, and facility floors. Buying some packs of plastic sheeting, dropping an apparatus into a plastic tray, or even just keeping a pack of towels handy are all great ways to stave off potential disasters.

Business/IP Risks

When I build prototypes for my own teams and clients, I take the “bus” approach. As in, “If I am hit by a bus tomorrow my team will still know what I did and why”. I label parts, organize my design folders with military precision and annotate my code obsessively. This is why I must put on a completely different hat when I’m building marketing materials. In the cut-throat world of startups, every potential partner can be a potential competitor, so controlling the release of confidential information, especially that which could be used to reverse engineer your idea, is a key priority. However, not everyone realizes just how much “confidential” information a good engineer can pull out of a few minutes alone with a prototype. This should be of particular concern when pitching to angels and venture capitalists, since more than a few got the job after starting out as “a really good engineer”.

What you can learn from a prototype: I can tell how fixed the design is by the materials and manufacturing marks, as well as if it has been designed for the production volumes listed on your slide deck. With a limited pool of specialized medical grade materials, there’s a good chance I can guess you materials by the color and feel. From the device size, complexity, and your general operations plans, I can narrow down the manufacturing partners you are in talks with. The standard consumables you’ve selected can disclose the sensors you’ve included in your diagnostic device.

Like a good pitch deck, only include in your prototype what you are confident in sharing. Since this will evolve over time as you develop relationships with investors, you should have a spectrum of prototypes. They start from the broadest “vision” of the product (a shiny box with no guts that gets you a return phone call) through demonstrating key features and your ability to solve the engineering challenges. Never just grab the latest version off the workbench. Good salespeople rely on high quality, purpose built “demo units” that support effective pitches. If you are also doing “sales”, but asking for a few million in prospective funds, you should take at least as much time preparing what you bring to your meetings.

Emotional/Human Rights

While the freewheeling bias toward action and experimentation at a startup has its place, some products have serious emotional and social implications that need to be acknowledged. Returning to my earlier story of self-experimentation, a key thing to note was that I performed the testing on myself. At no time was anything being done to me, or was I put under any pressure to do so. When the creative juices are flowing freely and you are part of a close-knit team, there is a real risk of being cavalier about the handling of other human beings. However, many of the problems we are trying to solve have left physical and emotional scars in those that have experienced them. Never assume you have all the information (let alone the permission) to safely place or remove something from a person’s body. Working with that assumption takes some planning and careful thought in designing your test experiences. Give your test participant as much control over the experience as possible, add extra time for building trust, and watch body language carefully. This doesn’t just keep your participants safe; it makes you a better researcher and (ultimately) a better designer.


How often do you think about “risk” when you are working on a prototype? Risk to yourself or other testers, risk to your facility or equipment, or even risk to your business? While in-depth risk analyses may not be appropriate for every build, take time to think about the general dangers the work you are doing involves. Work through these potential problems to identify root causes, then develop your own set of mitigations as part of your overall prototyping strategy.

About this Series

This is the 8th installment of a ten-part series on prototyping strategy. This is not about how to pick a 3D printer or get a nice finish on your painted parts, but a deeper reflective dive into the why and how we go about building the things that help us design better products. The points I focus on are not just to better align your project with some design "ideal", they are a way to manage the very real problem of every entrepreneur or program manager - build it fast, build it right, with as few resources as possible.

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