Trends in Membrane Switches for Medical Electronics
November 3, 2020
Membrane switches used in a medical application are customized products produced for use in laboratories, hospitals, and other medical environments. The membrane switches are used in a broad range of applications for daily usage in medical products, owing to its features such as quick response feature, low-cost of manufacturing, specific elastic properties, and its lightweight quality is projected to boost their end-use applications.
Switches are utilized in medical appliances such as self-serve kiosks, hospital equipment, handheld devices, patient monitors, lab equipment, and point-of-sale applications. These products are used with numerous other control systems including touch-based sensors, keyboards, smart lighting, switch panels in computers, Hospital Bed Controls, Infusion Pumps, Patient Monitoring Equipment, CT Scanning Equipment, X-Ray Equipment, MRI Equipment, Ultrasound Equipment, Nuclear Imaging Equipment, Dialysis Equipment, Drug Delivery Equipment, Blood Analyzing Equipment, etc.
With a large number of user interface options available today, it is easy to forget why the membrane switch is an excellent choice for medical instrumentation. The basic advantages are still the same as they were two decades ago when membrane switches became the interface of choice for a multitude of products in medical applications and portable devices. However, the advantages can be further enhanced by developments in materials, processes, and design expertise. These advancements can be:
- low profile
- easy to clean
- High degree of visibility with LEDs and electroluminescent panels
- Excellent resistance to adverse environments
- Antimicrobial film for protection against bacterial contamination
- Protection against electrostatic discharge by shielding
- Seal against water or chemicals
Trending in Membrane Switches
One of the common and proven methods of illuminating a membrane switch is through LEDs panels. The LED is a very effective way of communicating — either close or at a distance — a device status, even at oblique angles and differing light conditions. Advances in polymer surface mounted technologies, as well as commercially available low profile LED packages, offer a reliable and effective way to incorporate status indicators into a membrane switch. LEDs are best suited for status indicators but can be adapted to provide backlighting. This becomes a design challenge as the overall height of the switch is increased when using LED backlighting.
Electroluminescent (EL) lamps are not interchangeable with LEDs for lighting purposes. The EL lamp is most appropriate for backlighting in low light situations. The advantage for backlighting is an even light source (no point source of light is evident), and can be provided in a very thin layer.
Double-sided Polymer Circuitry
Membrane switches can easily provide protection against electrostatic discharge (ESD). An inner layer of the switch assembly can take such discharges to the ground. Innovative uses of double-sided polymer circuitry (D/SPC®) can provide the path to ground as part of the switch circuitry, thus eliminating the need for extra shield tails or tabs. The use of D/SPC can also help to reduce the footprint of the switch circuit, eliminating potential problems with discharges to the edges of the membrane panel. This shielding layer can simultaneously provide EMI/RFI protection.
Antimicrobial film on membrane switches has proven to be advantageous in protecting against any bacterial contamination taking place on the switchboard. It can be screen printed with common inks or embossed during manufacturing and can be used for clear window applications. When bacteria come into contact with this film, its antimicrobial function disrupts the bacterial cell wall killing or inhibiting bacterial growth. The result is that the film surface provides dependable and constant protection against bacterial contamination.
Impressive Aesthetics with Overlay Materials
Hard coated overlay materials have excellent resistance to adverse environments. Selective applications of texture coatings provide durable and pleasing background and interface areas while allowing lower layer displays to be highly visible and undistorted. In addition, lower layer displays and LEDs can be hidden using appropriate dead fronts and transparent colors. Embossing may be used to give the panel a three-dimensional look and feel.
Metal dome constructions are used for high reliability applications where a high number of actuations and extreme temperature cycling is anticipated. Metal domes are offered in a variety of sizes, shapes, and actuation forces. A second option is a formed polyester dome. Actuation force is highly customizable with this approach because there are numerous combinations of dome heights, sizes, and shapes.
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