Connect the dots – selecting the correct electric connector31 October 2014
As technology becomes increasingly interoperable, electric connectors play a vital role in advancing device capabilities. Medical Device Developments explores how manufacturers can select the right connector while ensuring a new product meets the necessary safety standards.
In the previous issue of Medical Device Developments, we looked into power supplies for medical devices and, specifically, the options open to OEMs that are building a new device and want to power up. This could be either via a medical-grade battery or, less commonly, via the mains.
While this part of the process is often left to the last minute, it's difficult to overstate its importance. When you're operating in a high-stakes medical situation, any outage really can mean the difference between life and death, so finding a reliable electricity supply is crucial. As we explored, this may entail adding a back-up power source and looking into custom-designed solutions.
For the purposes of that article, we treated each medical device as a stand-alone piece of equipment. However, healthcare environments do not consist of dozens of simple, discrete pieces of kit - interoperability is becoming more important, and different devices may form part of a larger system.
Similarly, many devices boast a high level of internal complexity. They need to be able to transfer data, signal and power between their various systems and peripherals.
This means that electrical connectors are just as critical as the ultimate power source. When developing or updating a product, manufacturers need to keep a keen eye on their cabling and connectors, and consider these elements when determining its overall risk profile. Here we run through some important considerations for OEMs looking to connect the dots.
There are many different options available, which can make it hard to select the right connector for the job. Depending on the function, these can be hidden connectors, which transmit power internally between the circuit boards of a single device; conventional connectors, which tie together systems and peripherals; or critical connectors, which link systems with functional devices. They can also be reusable or disposable.
Perhaps the first question to ask is whether you need something bespoke or if you would be happy with a commercial off-the-shelf solution. While custom connectors are more expensive than your typical design, they may be necessary if you have very specific application requirements. They can also tie into product branding - introduce an aesthetically striking and cleverly designed connector, and you have an additional opportunity to differentiate your device.
Where this isn't an option, some OEMs settle for a modified off-the-shelf solution, which can be a kind of halfway house. This is far cheaper than designing the whole connector from scratch but allows the introduction of some custom elements when necessary.
Generally speaking, as the med-tech sector evolves, so too do connectors. Designers are finding themselves under pressure to make their connectors as sleek and long-lasting as possible.
- Miniaturisation: medical devices are shrinking, with a steady shift towards portable, handheld applications. This means that connectors also must downsize, without losing any functionality in the process. In effect, designers are required to cram far more pins into a smaller space so as to retain the same signal density. The main way they are approaching this task is by reducing the spaces between the pins. With pins spaced less than 1mm apart, newer connectors can be more than 60% smaller than their predecessors. Since this trend is relatively new, it is important to closely check the specifics and maintain a dialogue with your supplier. While it is always tempting to opt for something small, sleek and easy to integrate, it's important to ensure your fun-sized connector can, in fact, carry the necessary levels of signal and power.
- Extending the lifespan: medical OEMs generally also want their connector to last as long as possible. From a design point of view, this means looking into mate life, or the number of times a connector can be connected and disconnected without sacrificing performance. While this is less of an issue for disposable applications, where a device will be used again and again it's important that the connector retains its function across the entire lifespan of the product. Recent solutions have focused on minimising unnecessary connections in the form of self-actuating connectors, quick-disconnect breakaway connectors and self-limiting designs. In other instances, engineers have taken advantages of new developments
in material science. The latest generation of connectors, with rugged nickel-plated aluminium housing, can last for at least 20,000 mating cycles without any performance drop.
While many of the points raised so far could apply across any sector, healthcare environments pose specific challenges that do not apply to, say, consumer goods. Manufacturers need to remain vigilant against electromagnetic interference and poorly sterilised equipment, as well as ensuring their connectors are highly durable. They should also consider human factors, such as whether the connector will be gripped with a gloved, and therefore slippery, hand.
- Sterilisation: as healthcare systems work hard to reduce hospital-acquired infections (HAIs), sterilisation is a critical concern. Connectors are no exception - they either need to be sterilisable or hermetically sealed. And because sterilisation methods are so multifarious, a connector in this setting needs to be able to withstand the likes of wipes, gamma radiation and autoclave to name a few.
- Durability: within a medical setting, it is particularly crucial that connectors are not torn off equipment or out of walls. To minimise these dangers, some connectors use breakaway features that impart an extra level of durability and reliability. They might feature a spring probe pin and pad contacts, which ensure individual pins remain electrically connected even when misaligned, as well as improving ease of cleaning.
- Signal noise: especially when it comes to devices such as patient monitors and pacemakers, it's important to shield against signal noise. This means using materials such as stainless steel and brass, as these have low magnetic fields and therefore do not affect signal clarity. Designers can also overmould the connector cable, which absorbs some of the disturbance as well as adding tensile strength. Shield-locking mechanisms and filter connections fulfil a similar function. Whatever you decide, medical devices are critical applications, and any problems with signal fidelity must be addressed.
By far the most crucial concern is safety. Medical device manufacturers need to have strategies in place to determine and manage their risk, which these days means following formal methodologies as part of the regulatory process.
When it comes to connectors, they need to mitigate the risks of electric shock and power failure. This is a nuanced task, and the specifics will depend on the job the connector is serving. Portable medical devices, for instance, will require finger protection and touch-proof connectors that keep the live parts out of harm's reach.
It also means thinking hard about cable selection - for instance, reducing silicone-jacket damage by adding a low-friction coating. Many OEMs choose to outsource this part of the process to a dedicated cable house that can manage their cable assembly from termination right through to overmoulding, sealing and testing.
- Regulation: as discussed in our previous article, FDA recently implemented new safety standards. Any medical device seeking approval in the US must now comply with the third edition of IEC 60601-1. This provides a safety benchmark for medical electrical equipment and requires manufacturers to have a documented risk management system in place. Designers can use design failure modes effects analysis (DFMEA) and also process failure mode effects analysis (PFMEA) to explore their risks and investigate whether their manufacturing process is up to scratch. They also need to engage with all the possible hazards right from the prototype or 3D modelling stage.
It seems probable that as medical devices become more sophisticated, their electrical connectors will follow suit. Two possibilities that hold promise for the future are hybrid and contactless connectors.
- Hybrid connectors: today's devices have more functionality than ever before, which means more connectors are needed. This, however, takes up valuable space. A new breed of integrated hybrid connectors has arisen, which can, for instance, combine electrical connectors with optical connectors for data transmission. These allow multiple functions within a single interface.
- Contactless connectors: we have heard it time and time again - devices are going wireless. As contactless technology continues to advance, intricate systems of cables and wires could soon be a thing of the past. Contactless connectors, currently in development, could transfer power via inductive coupling and would have no exposed electrical parts. This means they could be sterilised using intensive, high-temperature methods, making them ideal for use in a hospital setting. Connectors of this kind have already been developed for other industries, and it seems that the med-tech sector may not be too far behind.
Despite the staggering array of possibilities on offer, the task for medical device OEMs is clear: pick a reputable vendor you trust and with whom you can instigate a dialogue. With so many factors at stake, you need your chosen partner to be a jack of all trades, that takes risk management seriously while meeting your needs for sterilisation, durability and miniaturisation. As devices become more interdependent, it is more important than ever to make that connection.