Hygiene, functional safety and usability - keyboards in medical technology
Published in the meditronic journal 3/2021: Article as .pdf >>
The demands on devices in medical technology have always been extremely high. Inconceivable when a ventilator simply stops working, or when an input error in an infusion pump leads to an overdose. The three parameters are decisive here: hygiene, functional reliability and usability. Hygienically closed user interfaces with a high resistance to detergents and disinfectants are almost mandatory, because many viruses can survive on surfaces for several hours.
Depending on the field of application, the control devices are exposed to multiple people accessing them every day and can thus become a vector for disease. The MMI interface should also be reliable and easy to use. This is because, particularly in emergency situations where users are under time pressure and stress and often have to operate different devices at the same time, a complicated design can encourage incorrect input.
In addition to purely display-oriented operating technologies, classic input elements for controlling medical devices continue to play an important role. Whether ultrasound devices, patient monitors or bed controls - most human-machine interfaces in medical technology are still implemented or supplemented with a classic keyboard.
membrane keyboards

Because of its diverse design and equipment options is the classic membrane keyboard a preferred choice in the medical environment. A membrane keyboard consists of several individual layers that are placed on top of each other to form the overall structure. By using tools, it can take on almost any shape.
The decorative film, as the top layer, is made of extremely durable polyester or polycarbonate and is printed on the back to ensure the highest possible protection against abrasion. In addition, the material can be coated with a antimicrobial agent be supplemented and thus limit or eliminate the spread of germs.
Haptic feedback from membrane keyboards
The user benefits from a membrane keyboard from haptic feedback, so that user-related input errors can be avoided. For a safe finger guidance and tactile feedback ensure embossed buttons. In addition to the metal snap disks, there is also an acoustic feedback in the form of a “click” sound. The metal snap domes are available in a wide variety of sizes, shapes and actuation forces. They are preferred for applications with a high number of operations.
Capacitive solutions
Mechanical Sliders and knobs can also in one membrane keyboard integrated However, in hygiene-sensitive areas, a capacitive solution with a closed surface is recommended. This is because elevations, gaps and crevices that come with conventional controllers and encoders pose a high risk of contamination.
Cursor keys can also be capacitive solution be realized and replace the classic mouse as an input unit. Another advantage of this technology is an increased service life, since there is no mechanical wear. The user can also experience acoustic or optical feedback through the integration of LEDs or signal transmitters.
Touch displays with keyboard
If more complex menu navigation is required, the membrane keyboard can be equipped with a Touch display The membrane keyboard as a keypad allows quick access to recurring input commands or preset parameters, the touch display with its graphic visualization options enables interactive communication. To create a closed surface, the connection between the membrane and the display is realized by integrated viewing windows with a highly transparent adhesive layer.
Depending on requirements, these windows can be individually specified as glossy, matt, anti-reflective, scratch-resistant, UV-resistant and colored. The membrane keyboard takes on significant design aspects even when the black display is switched off. Even if functional reliability is the focus, product design is a factor in the purchase decision. It is also important to take intercultural differences between users into account. A red start button would be unusual in Germany, for example, but not in Asia.
Keyboard lighting
The room lighting in medical work environments is often dimmed, so that the lighting of input elements is essential for safe operation. Here she scores membrane keyboard through the easy integration of LEDs and the advantage of the printed surface, which can also be seen from a 180° rotated viewing angle.
The LEDs often function as status indicators for individual keys and are sufficiently bright even in daylight. But full backlighting of the membrane keyboard or individual keys is also possible through the use of LGF (Light Guide Film) possible. The typically flat design and flexibility are retained.
Within the LGF technology LEDs are inserted into an extremely thin, highly refractive film on the edge. Due to the high light refraction, only very few LEDs are required for homogeneous illumination. Each key can be backlit in different colors, and LGF technology does not require a high-frequency alternating voltage source.
A special feature are labels with vanishing effect. This is an inscription that cannot be seen when the keyboard is not illuminated and is only visible when it is illuminated. This can be used to signal a clear ON/OFF mode.
EMC shielding for interference-free operation
A reliable and trouble-free function of the input devices, is absolutely necessary, especially in medical technology. Membrane keyboards of all types are characterized by a long life span with over 1 million switching cycles. When using several electrical sources in one place, such as in the operating room, inadequate shielding against electrical or electromagnetic effects can lead to malfunctions and interference in the individual devices.
The EMC shielding membrane keyboard is realized, among other things, with an aluminum or copper-coated polyester foil. This shielding film prevents the device from malfunctioning due to the ingress of unwanted signals, as well as interference in its own electromagnetic environment. In connection with integrated displays, a segmented EMC shielding of the keyboard and conductor tracks is used.
Fully protected with silicone coating
In addition to the membrane keyboard as a control element, there is also a completely closed one, especially on handheld devices or desktop keyboards silicone coating possible. A flat keyboard layout is sprayed onto the front panel of the housing. After the electronics have been installed, they are welded to the back shell using an ultrasonic process. The result is an optimal bond between the individual components and a completely closed surface.
The keyboards are protected against water and dust ingress and thus allow complete and thorough cleaning. With a Protection class up to IP68 They are also suitable for immersion disinfection. Depending on the silicone used, steam sterilization is also possible. In conjunction with a membrane keyboard or a pure touch solution, the housing can be fitted with sprayed-on seals multi-component injection moulding be equipped.
The integrated seal ensures that there are no gaps that are difficult to clean and that the electronics are protected from the ingress of foreign bodies and liquids. With a well-coordinated design from the outset, a protection class of up to IP65 can be achieved.
In focus: High cost-effectiveness of membrane keyboards
advantage of Multi-component injection molding technology is also that only one component needs to be constructed. This significantly reduces the investment and the effort required for production and quality assurance. Ultimately, profitability always plays a role in every product. For example, the financial outlay for programming a graphical user interface between man and machine is a significant factor.
The rule is: Often not everything that is technically possible is also economical. Especially in devices with a small number of functions that require good visibility and constant user interaction, proven input components such as the membrane keyboard, hence the preferred choice. Due to the lower one-time tool costs, the costs remain significantly lower than for most alternatives - even for project volumes with small and medium-sized quantities.
Keyboard solutions have always been one of our core competencies and we support and advise you extensively on equipment and material selection. We can also take over the complete development and construction of the right keyboard for your application. We look forward to your inquiry!
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