Patient-facing medical devices

The recent launch of the Apple Watch Series 4 is the latest example of a device developed by a traditional consumer product company making a well-publicized entry into the patient-facing medical device market. Patient-facing devices include those used for screening, such as a thermometer; diagnosis, such as a blood glucose meter; treatment, such as a dry powder inhaler; and rehabilitation, such as a TENS (transcutaneous electrical nerve stimulation) device. As one of the world’s largest companies, Apple has the resources, technology, established brand language, and market presence to produce a desirable medical device. Successful innovations such as these raise patient expectations for what is possible across all types of products, including their medical devices.

Connected drug delivery devices: the reality of design and development

In this atmosphere, traditional medical device companies have been challenged to deliver similarly compelling user experiences — “challenged” being the operative word. Usability engineering and human factors engineering are relatively new practices in the medical device industry (as evidenced by IEC 62366 originating in 2007 and HE75 in 2009), which strive to balance the drive for satisfying interfaces against the safety and efficacy requirements of regulated devices. Through our work in consumer, medical, and crossover products, we have seen that positive user experiences lead to greater device acceptance, driving commercial and clinical success.

It is tempting to conflate user experience with product features, especially when consumers obsess over the image quality and responsiveness of a touchscreen and expect a certain level of connectivity in their devices. Such features are technologically impressive, but truly shine when they augment the user experience in a meaningful way. In a well-designed and well-engineered product, features don’t call attention to themselves, but rather seamlessly serve the overall value proposition the device is intended to deliver.

We know an exceptional user experience is driven by great product development and have identified some key considerations to enable that experience, which are outlined below.

Integrated product development

Product success begins with a development team where all disciplines are working in close collaboration and where the user and the technology are given similar priority during the development. Medical devices have historically been shielded from all but the most basic usability considerations. Traditionally, medical devices were necessary to reduce mortality, morbidity, or improve quality of life; had little competition; and were not typically chosen or purchased directly by the end users. In contrast, consumer products are generally discretionary purchases, have a significantly lower barrier to entry, and are marketed directly to consumers.

Close collaboration between disciplines is necessary to avoid sacrificing the user experience in favor of advancing the technology. It is the difference between team members working towards a specification or working towards a shared vision. For example, if a requirement specifies a certain response must take less than 10 seconds to be accepted by patients, and the technology actually takes 12 seconds, an adaptive and collaborative team can turn that apparent failure into a success by reimagining the workflow, combining functionality, or allowing tasks to run in parallel so the user gets a greater perceived value for that time and is less concerned with exactly how long it takes, so long as those additional two seconds are not governing something safety-critical.

The importance of a shared vision cannot be overstated and having someone on the team responsible for a great user experience is of paramount importance in delivering on that shared vision. On a recent autoinjector development, many engineering features were proposed as tradeoffs against the physical size of the device. However, we knew through user research that the intended users had a strong preference for a small device, and growing it in any direction, even if only by a millimeter, would lessen its desirability and acceptability. Having a vision for the overall size of the device, and empowering someone to enforce it, meant that a vital aspect of a positive user experience was preserved.

Close collaboration also enables more frequent, more rapid ‘mini iterations’ during product development that would not otherwise be possible. A conversation among key members of the development team can quickly generate ideas for overcoming a development block. Having the right participants and a shared vision can make it easy to down-select one or more of those ideas to bring forward. Having these real-time, tight design loops can make the difference between an acceptable device and a desirable device. Close collaboration also means more than just people. It also means that the tools the development team is using must facilitate interaction with minimal overhead.

Reduce size everywhere

Physical size is one of the key drivers for desirability in patient-facing medical devices. Having a continuous glucose monitor the size of an early-2000s mobile phone does not inspire devotion when patients encounter many more attractive and more compact consumer devices daily. One common refrain is that medical devices are “bulky” compared to their consumer counterparts. One of the ways to avoid this is to have a defined design vision, as described earlier that drives, and is reinforced by, every decision made during development. That design vision can be supported by engineering work to keep the size down throughout the design process, particularly when specifying components and considering assembly techniques.

In addition to increased desirability, a smaller device has other beneficial side effects such as lower power needs and less material use overall, leading to reduced product weight. From a component standpoint, using thin flex PCBs that can be bent or folded to fit a particular profile can go a long way in managing device size. Using electronic components in the smallest packages can also help. For a more extreme approach, bare die components and ASICs may further pare down the size. User interface components on the PCB can also be miniaturized, though there are practical limitations to the sizes of the interfaces themselves. Finally, laser direct sintering can be used to fabricate circuit traces directly onto the surface of another plastic part with no practical impact to the overall dimensions, thus enabling creative antenna and PCB solutions. These size reduction methods often come at a higher cost, either in non-recurring engineering or piece prices. Striking the right balance is one of the challenges that an integrated development team can manage.

From an assembly standpoint, the easiest way to manage size is to eliminate as many fasteners as is feasible from the design - housing a fastener requires a wall thickness on either side of the fastener, plus the dimensions of the fastener itself. Substantial space savings are possible with ultrasonic or laser welding and appropriate adhesive use. Project planning should account for the time required to develop these processes.

The right components and materials

The industrial design of the device is a significant factor in determining its desirability to patients. Industrial designers are responsible for keeping up with user expectations and teasing out timeless vs. trendy design. At this writing, smart phones are becoming monolithic, with the front face consisting almost entirely of the touchscreen display. High end plastics provide a sleek look while also serving to protect the device. They are frequently injection molded with thin walls in high pressure machines. Touchscreen displays often feature a dead front look and indicator LEDs illuminate icons that are invisible until lit. Yet, medical device production rarely reaches quantities typical of smart phone manufacture, which puts medical devices at a disadvantage compared to consumer products that can amortize the high, non-recurring costs needed to produce some of these desirable effects. Still, medical devices can take advantage of products and processes used in the consumer world, but at some risk. For stock components such as a touchscreen display or battery, it rarely makes economic sense to develop a custom component for the product. A compromise can be to have a custom part number of an otherwise stock component for traceability and regulatory purposes. Capitalizing on a commonly available mobile phone display or battery may lead to the benefits of scale with minimal initial cost. However, as a small customer, sourcing such components for a medical device is subject to the market whims of larger consumer product companies and it is difficult to secure a supply chain with relatively small orders. In addition, consumer products have a much shorter service life than medical devices, which leaves them less susceptible to supply chain issues.

In one drug delivery device development program, a battery selected for its specific dimensions went end-of-life during the development with no drop-in replacement available. The team had to make size/power tradeoffs to implement another battery in its place. Large medical device and pharmaceutical companies may be able to exert some leverage by using their name recognition to overcome such obstacles. Smaller companies without such advantages may have to resort to lifetime buys or look to their contract manufacturers for help, though neither is a sure thing. Planning for such eventualities based on a program risk assessment may be the best way to maintain component flexibility during development.

Much of achieving a desirable user experience can be accomplished via smart design, thoughtful material selection, and clever manufacturing processes. Specialty plastics, thin wall or multi-shot injection molding, and finishing techniques that include things like physical vapor deposition can all increase the perceived value of a product, but at the cost of tooling and the time needed to develop the process to achieve the desired look and feel. As patient expectations increase and health care industry and reimbursement models evolve, competition may induce medical device companies to view such extra investment as worthwhile.


Desirable products need technical and user representatives on the design team who work closely together to manage tradeoffs. We have seen this development practice result in positive user experiences, greater device acceptance, and clinical and commercial successes.


Matthew DeNardo
Principal Engineer