Silicone switch mats vs. membrane keyboards in medical technology
A decision-making aid for developers
Published in Meditronic 05/2023 Article as .pdf >>
In medical technology, keyboards and user interfaces are an indispensable aspect of device design. These components must not only be functional and reliable, but also meet the high standards of hygiene and usability required in clinical environments. From ultrasound devices to patient monitors to bed controls, the human-machine interface is a critical factor in the quality of patient care. Hygiene is the top priority when it comes to medical keyboards. Pathogens can persist on surfaces and potentially lead to infections. This makes it essential to use materials and technologies that are easy to clean. In addition, these surfaces must be resistant to aggressive cleaning and disinfecting agents commonly used in medical facilities.
Classic input components: membrane keyboards and silicone keypads
Classic input components are usually used: membrane keyboards and silicone safety mats. Both technologies have their own strengths and weaknesses, and choosing the appropriate keyboard solution depends on a number of factors, including volume, budget, technical requirements and the specific application of the device.
Structure of a membrane keyboard
membrane keyboards
membrane keyboards are often the first choice for applications where a flat input solution and easy installation is desired. They can often be integrated by gluing them onto a standard housing, making them particularly attractive for applications where quick solutions or adjustments are required. The membrane keyboard consists of several individual layers that are put together to form a very flat overall structure. Using special printing techniques, more complex circuit diagrams can be printed directly onto the film. The top layer is often made of durable polyester or polycarbonate and can be treated with antimicrobial agents to limit the spread of germs. Embossed keys provide haptic feedback that minimizes user-related input errors. In addition, metal domes can provide acoustic feedback through a “click” sound, which is particularly beneficial in high-frequency environments. The integration of flat signal transmitters is also possible for acoustic feedback.
Membrane keyboards in medical applications
Illuminated membrane keyboards
Room lighting in medical work environments is often dimmed, so lighting input elements is essential. The membrane keyboard scores points here thanks to the simple integration of LEDs for backlighting key symbols or for status messages. In addition, the user also receives visual feedback through integrated LEDs.
More complex menu navigation can be achieved by adding the membrane keyboard with one Touch display be facilitated. The membrane keyboard allows quick access to recurring input commands and preset parameters, while the touch display offers graphic visualization options for interactive communication.
Compatibility shielding (EMC) for membrane keyboards
When multiple electrical sources are used at the same time in one place, such as in the operating room, inadequate shielding measures against electrical or electromagnetic influences can lead to impairments and disruptions to the individual devices. To ensure trouble-free function of a membrane keyboard in this environment, electromagnetic compatibility shielding (EMC) is used, which consists, among other things, of a polyester film coated with aluminum or copper. This protective film not only prevents unwanted signals from entering the device, but also minimizes possible interference in its own electromagnetic environment. In terms of price, membrane keyboards have an advantage over silicone keypads for small to medium quantities because they require less initial investment.
silicone keymats
Silicone safety mats in medical applications
Hygiene requirements
Regarding hygiene requirements, the use of silicone keymats initially appear to be suboptimal in medical technology. The particular concern is potential cavities and joints that could arise when integrated into a housing. These could supposedly not be sufficient to meet the high hygienic standards of medical technology. In addition, the initial investment in tools and molds for silicone safety mats should not be underestimated, which makes them expensive for small series. However, it turns out that silicone safety mats are used at higher production numbers remarkably more cost effective as membrane keyboards.
Button design of silicone keypads
Silicone safety mats for flexible design
Another crucial one Advantage of silicone safety mats consists in their extraordinary Design flexibility and adaptability. In contrast to membrane keyboards, which have physical limitations, particularly in the spatial extent of the keys, silicone keys offer considerable freedom in design and enable keys with a height of several centimeters. This flexibility extends across a wide range of possible applications: from variable key shapes and key sizes to individual color options and specific surface structures. In addition, targeted elevations or depressions in the keys enable differentiated haptic feedback, which significantly improves the user experience. In addition, special surface coatings such as polyurethane (PU) or epoxy resin offer lasting protection against mechanical abrasion.
Also the integration of modern lighting technologies such as Status LEDs or backlighting in combination with transparent elastomers is possible without any problems.
To effectively seal gaps and gaps in the housing and protect the underlying electronics from moisture, individual keys can be equipped with peripheral seals. This is a critical factor, especially in medical environments where regular cleaning and disinfection of equipment is essential.
More about silicone safety mats? – Item: Silicone safety mat – A classic with future potential
Multi-component injection molding technology for diverse integration
The Overmolding process also opens up completely new perspectives, especially with regard to handheld devices, desktop keyboards and larger operating devices such as ultrasound devices. A flat keyboard layout is applied directly to the front panel of the case. After the electronics have been installed, they are welded to the back shell using the ultrasonic process. This results in a seamless connection of the individual components and a surface that is completely finished.
The resulting keyboards are highly resistant to water and dust ingress and therefore allow for thorough and comprehensive cleaning. With a Protection class up to IP68 Immersion disinfection is even possible. Depending on the choice of silicone material, steam sterilization is also possible, which can largely alleviate any initial concerns about hygiene suitability.
Patient bracelet in multi-component injection molding with injected button layout
Another feature of the Multi-component injection molding technology is the Manufacturing efficiency: Here only one component needs to be developed and produced. This not only reduces the initial investment, but also significantly reduces the resource expenditure for production and quality assurance. The scalability of this approach can often more than offset the initial costs of tools and molds, making this method as one economical alternative to separate membrane keyboards and housing components.
Front panel with molded keyboard layout and integrated connectors
In addition, the technology allows seamless Integration of additional functional elements such as magnetic connectors, which only require a minimal installation depth but ensure a robust connection. This simplifies the design logic and optimizes the space required in the device. In medical applications, thanks to their easy-to-clean and disinfectable surfaces, these connectors offer a convincing alternative to conventional connector systems whose corners and edges could pose a risk of contamination. Their cleaning efficiency can even be increased by using special seals or directly overmolding the connector.
Not a simple either/or
Both membrane keyboards, as well as silicone keymats offer high durability and reliability, which is why choosing between them is not a simple either/or. Rather, it requires a careful analysis of the specific needs of the respective medical device. Factors such as usability, context of use and cost structure should be considered in a holistic approach across the entire product life cycle in order to select the most optimal keyboard solution. In this complex decision-making landscape, both membrane keypads and silicone safety mats, especially when combined with multi-component injection molding, can be technologically and economically convincing options. The final decision ultimately depends heavily on the individual requirements and needs of the respective project.
Full service at N&H Technology
We will work with you to develop the optimal input solution for your application. We are also happy to take on the design and development and accompany your project from the initial idea to series delivery. More about our service >>
