From traditional press-down devices, to today’s touch screens, we have grown accustomed to making technological commands with the simple movement of a fingertip. The world of medicine and health has some very specific requirements for such systems, requiring robust, easily cleaned devices that can even be used by gloved hands, as Dieter Matter of ALGRA, a company specialising in input technology, explains.

Today, we are accustomed to entering commands into a device using our fingertips. Admittedly, touch screens have taken this from the traditional press-down finger click to more of a ‘tipping and wiping’ motion, through various menus. Nevertheless, sometimes we are just glad to be able to make a simple, clear and accurate input with a distinctive finger press.

The medical field has several particular requests which exceed the common requirements of human machine interfaces (HMIs). For medical uses, these need to be:

  • applicable with gloves
  • easy to clean
  • resistant to disinfectants
    able to function reliably under the impact of water or other fluids.

Piezo fingertip-input technology is highly suited to fulfilling these challenging demands. Piezo contains the properties to generate or detect tiny movements in the range of micrometres. Used as a sensor, the micromotion generated by a fingertip is sufficient for detecting input. This is not affected by the operator wearing gloves, or if the surface is wet, such as following a spill.

If the operator unintentionally wipes over the input surface, no signal is triggered. To generate a signal, a distinctive finger tip movement of a few micrometers in the key area is needed. The surface can be designed completely flat, without any gaps or grooves that collect dirt.

Significantly, the function of this HMI is independent of which material is used for the front of the interface. Metal, plastics, glass or other materials can be used as an input cover, for reasons such as:

  • to reach an elevated hygiene standard
  • to create a unique design
  • to resist harsh environments.

The materials typically used are stainless steel, aluminium with an anodised graphic layer, glass or plastics printed from reverse side to resist harsh impacts. There is just one limit: the thickness of the front layer, depending on the material; it is 0.3-1.0mm for metals and glass and 0.5-2.0mm for plastics.

The company ALGRA in Switzerland, with more than 30 years of experience, specialises in making customised piezo input systems. Technology, production and engineering are combined under the same roof, ready to meet customer’s requests comprehensively.

During past decades, ALGRA has developed two piezo input devices: Dynapic and Dynasim.

Dynapic, with inserted piezo disc

The device offers the following advantages:

  • ultra slim (switching package up to 0.5mm)
  • seamless
  • has a top layer of metal or glass up to 1.0mm, or of polymer up 2.0mm; extra measures and thickness are possible
  • can be made with various alternative materials for the front design layer
  • suited to harsh environments and outdoor applications
  • comes with key illumination.

Dynasim, with printed piezo ceramic layer

Alongside the Dynapic, the Dynasim:

  • is even slimmer (switching package up to 0.3mm)
  • is seamless
  • offers a large cost advantage for a higher quantity
  • has a top layer of metal up to 0.7mm, glass up to 0.5mm and polymers up to 1.2mm
  • is suited to harsh environments and curved surfaces
  • comes with key illumination.

Customised input systems

ALGRA has encounted many different applications and has gathered extensive experience; this is used to meet its customers’ requests comprehensively. With engineering and production skills, each type of piezo keyboard has been proven to last.