Feature Article

Smooth and flat can reduce infection
Public concerns surrounding infections such as swine flu, Methicillin-resistant Staphylococcus aureus and Clostridium difficile focus attention on hygiene and cleanliness, particularly in hospitals. Placing renewed emphasis on routine cleaning of surfaces to control the spread of pathogens and improving the design of hospital equipment to facilitate cleaning can help to increase protection for patients.

During normal use, organic materials can be deposited on equipment such as scanners, operating room monitors and electronic surgical instruments. Cleaning can be difficult, however, especially around controls such as switches and buttons with their associated cutouts and bezels. Replacing these mechanical devices with touch-sensitive screens presents a potential remedy. These enable a completely smooth control panel that offers no harbour for bacteria and supports easy, wipe clean hygiene. Moreover, touch screen ergonomics, including the use of light and colour, will allow designers to create new generation equipment that offers improved usability. This will increase patient safety still further by enabling medical specialists to work quickly and efficiently with reduced risk of human error.

Optimum ergonomics
The latest generation of consumer devices such as smart phones and portable media players already utilise touch-sensitive controls to simulate sophisticated features. These include, for example, rotary dials, slider controls and the pinch-and-flick functionality that allows users to navigate menus as though flicking through a book. Depending on the type of device, the touch sensor may be positioned in front of the powered display to enable the user to interact directly with onscreen graphics. Alternatively, one or more touch sensors may be implemented in fixed positions and their locations indicated with printed icons. Both these types of control panel can be enhanced with the use of coloured illumination to highlight various controls and indicate when a touch has been detected.

Distributing illumination such as from a high-brightness light emitting diode (LED) to a defined point on the control panel’s surface has always challenged engineers. A separate printed circuit board (PCB) populated with top-emitting LEDs and mounted directly behind the control panel is often used. This complicates assembly and also increases overall size and bulk. Using an injection-moulded light guide to channel light to the desired locations can allow the LEDs to be mounted remotely in a more suitable place; however, a PCB is still required and tooling costs are usually prohibitive at the low volumes typical of hospital equipment.

Printed light guides
New production technology for light guides combines proven processes from the membrane keypad industry with patented innovations and eliminates the heavy initial investment in tooling for injection moulding. It is now possible to build low-profile light guides that are capable of generating uniform illumination over a large surface area to deliver a high quality result.
An illuminated control panel utilising this technology can be built as a single, multilayer unit comprising a flexible PCB, side-emitting LEDs, screen-printed light guides, a capacitive touch sensor and an outer graphic. A flexible tail
connects the panel electrically to the equipment controller. The total thickness can be less than 1 mm.
Large numbers of side-emitting LEDs can be positioned at the edges of the assembly, which allows designers to create segmented patterns of light in locations corresponding to touch-sensitive areas on the surface. Colour mixing is also possible, which provides extra opportunities to create effects such as warnings or change of status or, for example, to emphasise certain options at various junctures in a procedure.

Adjusting the LEDs dynamically, under the control of the application software, allows touch controls such as buttons or switches to change colour or brightness when activated. Sliders or rotary controls can be illuminated on a segment-by-segment basis to reflect the current setting. “Normal” or “condition critical” signs for various monitored levels can be displayed. Other effects such as “hidden-until-lit” controls to simplify operation or to help prevent operator errors are also achievable using this technology.

Increasing hygiene and safety
The enhanced ergonomic opportunities gained from printed light guides make this technology a critical enabler of totally smooth control panels that eliminate hard-to-clean features, yet also deliver interactivity and ease of use for medical specialists. As a result, patient safety can be increased in two ways by protecting against hospital infection and by assisting surgical speed and accuracy.

Iain Kyle is Business Development Manager at
Design LED Products Ltd, Alba Innovation Centre, Alba Campus, Livingston EH54 7GA, UK, tel. +44 1506 592 310,
e-mail: info@designledproducts.com  
www.designledproducts.com