Keyboards in medical technology

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 operating devices are exposed to several people accessing them every day and can thus become a carrier of diseases. In addition, the MMI interface should have reliable functional safety and intuitive usability. Because especially 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 entries. In addition to pure display-oriented operating technologies, classic input elements for controlling medical devices continue to play an important role. It doesn't matter whether it's 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

Membrane keyboards medical technology

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 and thus result in the overall structure. With the use of tools, it can take almost any shape. The decorative film, as the top layer, consists of extremely hard-wearing polyester or polycarbonate and is printed on the back to ensure the best possible protection against abrasion. In addition, the material 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

Senso-Touch membrane keyboard

Mechanical Sliders and knobs can also in one membrane keyboard integrated however, a capacitive solution with a closed surface is recommended in hygiene-sensitive areas. Because it is precisely the elevations, gaps and crevices that conventional controllers and rotary encoders bring with them that harbor a high risk of contamination. Cursor keys can also be used with a 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 with one Touch display be added. The membrane keyboard as a keypad allows quick access to recurring input commands or preset parameters, the Touch display interactive communication with its graphic visualization options. For a closed surface, the film and display are connected by integrated viewing windows with a highly transparent adhesive layer. Depending on the requirements, these windows can be individually specified with a glossy, matt, anti-reflective, scratch-resistant, UV-resistant and colored finish. The membrane keyboard takes over significant design aspects even when the black display is switched off. Even if the focus is on functional safety, the product design is a factor in the purchase decision. It is also important to consider the intercultural differences of the users. A red start button would be unusual in Germany, for example, but not in Asia.

Keyboard lighting

Membrane keyboard with disappearing effect

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 that can also be seen from a 180° rotated viewing angle. The LEDs often function as a status display for the individual keys and are sufficiently bright even in daylight. But full-surface 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 at the edge in an extremely thin, highly refractive film. Due to the high refraction of light, only very few LEDs are required for homogeneous illumination. Each key can be backlit in different colors, and the LGF technology does not require a high-frequency AC voltage source. A special feature are inscriptions 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.

Absolutely reliable input solution

An 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. If several electrical sources are used in one place, such as in the operating room, malfunctions and faults in the individual devices can occur if there is insufficient shielding against electrical or electromagnetic effects. 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

Membrane keyboard with EMC shielding

In addition to the membrane keyboard as a control element, especially with handheld devices or desktop keyboards, there is also a completely closed one silicone coating possible. A flat keyboard layout is injected onto the front panel of the case. After the electronics have been installed, they are welded to the rear 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 enable 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 connection 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. A protection class of up to IP65 can be achieved with a well-coordinated design from the outset.

In focus: High cost-effectiveness of membrane keyboards

Silicone keymat on front frame

advantage of Multi-component injection molding technology is also that only one component has to be designed. This significantly reduces the investments and the effort for production and quality assurance. After all, profitability always plays a role with every product. For example, the financial outlay for programming a graphical user interface between man and machine is a not inconsiderable factor. The following applies: Often not everything that is technically possible is also economical. Especially in devices with a small number of functions, which at the same time require good visibility and are in 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!


Specialist article on input keyboards

Multisensory membrane keyboards in medical technology
Capacitive membrane keyboards: Traditional design combined with touch technology
Silicone switch mats vs. membrane keyboards in medical technology - a decision-making aid for developers
Efficient input in a small format - versatility of membrane keyboards and silicone keymats
The silicone keymat: A classic with future potential
Keyboard solutions for industry
Keyboards in medical technology
Membrane keyboards – the perfect addition to touch
Does the conventional keyboard have a future?
Advantages of membrane keyboards