Is there a medical device inside James Bond’s Rolex?

Unscrew a hermetically sealed Rolex case and you will discover a complex and intricate mechanism that is comparable in some ways to the inside of a disposable inhaler device.

 
It may come as a surprise that hidden within a Rolex watch we have also found a medical device – well, perhaps more figuratively than literally. But unscrew a hermetically sealed Rolex case and you will discover a complex and intricate mechanism that is comparable in some ways to the inside of a disposable inhaler device.

Outwardly the engineering of disposable medical devices, such as inhalers, does not appear to share much with the intricate mechanics, ultraprecision and lavish materials found in watch mechanisms. Even so, medical device engineers tackle similar technical challenges as the watch designers, employing engineering excellence, skill and craftsmanship to deliver a product which maintains a balance of the user needs, unfailing performance and overall safety.

Even without Q’s aftermarket modifications Rolex watches radiate an aura of high-quality engineering and luxury. As Rolex states on their website:

“Rolex watches are crafted from the finest raw materials and assembled with scrupulous attention to detail. Every component is designed, developed and produced in-house to the most exacting standards.”

These components are made of many interesting and exclusive materials such as ceramic, titanium, gold and even jewels – some are embellishments, but some have special qualities like hardness for low friction bearings. The most basic Rolex requires 115 different pieces to be assembled with precision.

Over the years, the development of wrist watch movements has been more about evolution than revolution: characteristically they use energy derived from a wound flat steel band (the mainspring). This energy is transmitted to the oscillating section of the watch (called the balance) by a gear train and escapement, and consequently to the rotation of the watch hands.

It would be an understatement to suggest that the manufacturers of inhaler devices and Rolex watches are anything but obsessed by product quality; for both, it is essential that all products leaving the factory are defect free. But there are some big differences in how the quality of the final products is ensured.

Rolex prefer to take a hands-on approach to both product assembly and testing. They ‘quality-control’ their watches for accuracy by simulating wear before they are released to the retailers. Of course, some of the testing is automated, but the fact that it is done on every one of the watches and that it takes several days to complete, means that it is not an approach that many other industries can adopt; especially those mass-producing products such as medical devices.

An advertisement for Rolex once claimed that it takes about a year to make a single Rolex watch. This is almost certainly untrue, but it does highlight that Rolex customers believe that a slower production rate implies a higher quality product.

GSK are making and shipping over 60 times more devices per year at a product cost that is approximately 2,000 times cheaper than a Rolex.

 
On the other hand, medical device engineers will design safety-critical products for high-speed manufacturing – as high as one per second, not one per year – from the early concept stages.

The care and craftsmanship of the component parts is achieved in a very detailed production method which could be compared to that of high-end watches. But device developers follow a rigorous and detailed process of analysis, trial and verification to ensure that the final design intent is suitable for industrialisation (production scale-up).

Later, the manufacturing processes are validated to demonstrate, and prove statistically, that the final product will consistently meet specification, irrespective of all the possible manufacturing tolerances and variables. In this way quality is assured rather than controlled.

As an example, a discus type inhaler has 12 plastic components – plus a blister strip – and over 7,500 inhalers can be made per hour by just one production line at a GlaxoSmithKline site (over 68 million per annum). In contrast Rolex produce about 1 million watches per year across all their brands.

This means that GSK are making and shipping over 60 times more devices per year at a product cost that is approximately 2,000 times cheaper than a Rolex.

On the surface DPIs appear to be ‘low-tech’, however, just because they are perceived as basic and cheap compared to wrist watch mechanisms it does not mean that the engineering and development that goes into them is any simpler.

GSK’s Ellipta®, another DPI device, is designed to be used once-daily for the delivery of both mono- and combination respiratory therapies and can hold up to 1 month’s supply (30 doses) of medication.

From the outside, the device is quite plain, the external case is white with a coloured mouthpiece cover to indicate the drug type. There is little in the way of embellishment except for some small ridges, which exist to indicate to the user the simple mode of operation (open, inhale, close), and a small counter to display the number of doses remaining. However, the basic shell conceals a complex internal gear mechanism that is comparable in intricacy to many watch movements.

To prime the Ellipta device the user opens the mouthpiece cover, by this single movement and hidden to the user, the device mechanism simultaneously performs five actions:

• Advances the blister strip and aligns a blister with the mouthpiece manifold airflow path;
• Peels the blister foil laminate to expose the contents of the blister(s) for inhalation;
• Gathers the used portion of the blister foil laminate;
• Drives the dose counter gears to move the dose counter display by a one unit decrease;
• Provides an audible ‘click’ at the end of the mouthpiece cover movement.

What is remarkable is that the gears inside the mechanism are all plastic and are mass-produced on multi-cavity injection mould tools; they are not made of precision-machined and hand-finished materials as you would find in a Rolex mechanism. This means that each part has a natural variation, caused by small fluctuations in the moulding process. That variation is multiplied by the number of tool cavities, with each mould cavity very slightly different from the next.

For a device like this, which is manufactured in high numbers, there will be at least three sets of tools to allow for repairs and refurbishment. When you consider the potential combinations between interacting parts, the permutations become significant. This places a high demand on rigorous engineering in design and manufacture to accommodate the part-to-part variation and most importantly, their interaction, to ensure the device functions correctly every time.

The functional challenge with watch engineering is mainly to do with maintaining a consistent movement with very low friction and wear. The gear trains in DPIs also feature solutions that are similar to those found in wrist watch movements; features like idler gears, ratchets and escapements can be found, but unlike a watch mechanism, it is not always appropriate to have liquid lubricants in systems because they may be inhaled by the user.

The plastic materials used in the DPIs have been chosen to optimise their frictional performance whilst they are still able to be moulded with high precision. However, the pool of materials is limited further, as the plastic components are made from a relatively small range of medical grade polymers that have the appropriate USP class IV and ISO 10993 certification for use in medical applications.

The mechanism design for both Rolex watches and mechanical inhaler devices is based on broadly the same engineering fundamentals. The engineers for both products carry out analytical analyses using the same basic equations and principles, some common examples are:

• The involute gear equations – used to describe the interactions and forces between involute gear teeth profiles.
• Hooke’s law – to describe spring constants.
• Coefficient of friction – which describes the ratio of the force of friction between two bodies and the force pressing them together.

Occasionally it is interesting to draw similarities across industries, because after all ‘engineering is engineering’, whether it be for James Bond gadgets, Rolex watches or medical devices.

Comparing DPI design to Rolex watches – two seemingly very different products – helps to paint a better picture of the complexity and challenges that medical product engineers tackle and overcome. It is worth remembering that the best examples of engineering design are sometimes the ones that remain hidden from view and are concealed inside the plain and functional devices that we use daily; or to put it into 007’s words:

James Bond:
You know, you’re cleverer than you look.

Head of Q-Branch:
Still, better than looking cleverer than you are.