DATA MODUL Press Release
Input methods in medical technology
Author: Markus Hell, Managing Director Products & Markets at DATA MODUL
Human machine interface, or HMI, has become such a commonplace that the importance of user friendliness of devices is often underestimated. In the current demanding field of medical technology, the HMI plays a particularly important role. When it comes to input devices and displays in medical applications, the usability aspects – for example in daily use in hospitals or medical practices – are often considered first. One of the greatest challenges with these applications is in particular an input option that is at the same time hygienic, sterile and reliable. As the safety of patients and hospital staff is of utmost priority, the requirements and specifications in medical technology are much higher than in consumer segment. All devices and input surfaces must therefore be kept as sterile as possible, while ensuring an error-free operation even under difficult input conditions, such as when the user of the device is wearing surgical gloves. DATA MODUL offers tailor-made solutions specifically for the medical sector, manufactured in compliance with the medical standard ISO 13485: 2016.
PCAP in medical technology
Due to their numerous advantages, PCAP (Projective Capacitive Touch) systems have in recent years found their way into both private and professional sectors. This intuitive input option, to which users have become accustomed from using modern mobile phones, is also becoming increasingly important in the field of medical technology.
The functionality of a PCAP system is based on a matrix of capacitively coupled transmitting and receiving electrodes that are attached to the display. The signals at the receiving electrodes are continuously scanned. If a conductive object – e.g. a human finger – approaches the sensor, the measured signals change. This change is detected and the position of the object calculated from it.
When using a PCAP system, the focus is on two basic requirements: input must be possible at any time and regardless of external influences, and at the same time no false triggering may take place due to, for example, external interference. These external interferences can be of an electrical nature and may for instance be coupled in via the supply lines. Conductive liquids such as saline solution, blood or sweat can also be the cause for false triggering, as their influence on sensor values can be very similar to that of a human finger. To distinguish these unintended influences from intended influences, one would require a state-of-the-art PCAP system with a high performing touch controller IC as well as the experience to deploy these systems in an optimally coordinated manner. The latest generations of these controllers, also offered by DATA MODUL, use sophisticated algorithms to respond to the demands of medical technology.
The touch system and the choice of the right user interface
Besides the synthetic material PMMA, glass is the most frequently used touch surface. A suitable cover glass can help to meet the stringent requirements for medical devices and their operation. The cover glass also provides protection and serves as a carrier for the PCAP sensor. Such cover glass is available in different thicknesses, properties, printing and shapes. Since the touch sensor can be bonded individually to any type of cover glass through the use of optical bonding, there is great flexibility in the design of the glass. In addition, glass offers a high degree of chemical resistance, which makes thorough cleaning and disinfection possible.
If necessary, special antibacterial or antimicrobial glass surfaces can also be used for medical applications. The upper layers of such glasses contain ions which kill up to 99 percent of the micro-organisms on the glass surface and thus prevent them from spreading – even after prolonged use. In addition, these types of glass are highly resistant to mechanical and environmental influences such as UV radiation. The glass, even after long periods of use, retains its full transparency and at the same time guarantees the protection of the underlying components.
Another aspect to ensure maximum sterility is the sealing between the cover glass and the monitor housing. The production-related gap between the cover glass and the frame is closed with a polymer adhesive during a process called gap filling, thus preventing bacteria and dirt from entering the device. At DATA MODUL, this process is fully automated and performed under clean room conditions. The result is touch devices that have the highest industrially achievable hygiene standard and guaranteed sterile, hygienic input.
Avoiding direct contact as a preventive protective measure
Control panels with direct contact – such as the PCAP systems just mentioned – represent a particular challenge for medical input devices in terms of hygiene, as the transmission of germs, viruses etc. often takes place through surface contact. There are a number of ways to minimise the risk of transmission to humans via the HMI system. One possibility that is widespread in the medical field is to avoid direct contact with the surfaces.
Gloves are often compulsory in medical technology, as they are a simple means of protection against contamination, infection and the transmission of diseases and pathogens. However, if normal operation of a touch screen should be maintained even when the user is wearing gloves, the touch controller must be configured accordingly. These gloves range from thin medical nitrile or latex gloves to thick work gloves. DATA MODUL offers the support of experienced field application engineers who parametrize the touch controllers for every application according to customer wishes and requirements. The result is that there is no difference between operating the device with or without gloves.
Another way of avoiding direct contact with the touch sensor is with input pens – so-called stylus pens. These allow very precise inputs on many types of touchscreens without direct contact to the skin. There are two kinds of input pens – active and passive. Passive pens merely have a tip made of a conductive material and thereby replace the fingertip. These pens are independent of touchscreens – i.e. the pens can be used on any touchscreen as long as it is configured for this screen and has a corresponding resolution. Active pens are usually coupled to specific touchscreens and can only be operated on corresponding screens.
Compared to operating a touch screen with gloves, touch pens have the advantage of guaranteed sterile environment without the inconvenient handling of gloves.
Methods of contactless input – optical, acoustic or capacitive?
In view of increasing hygiene standards and safety requirements, contactless operating options offer practical added value. Although these so-called “hands-free” methods cannot yet completely replace conventional touchscreens, they are particularly suitable for special applications in which any contact and possible contamination of surfaces should be completely avoided. The most common solutions for contactless input are acoustic or optical input methods or by means of capacitive sensors.
Eye tracking opens up new possibilities in medicine
When it comes to optical solutions, options include camera-based technologies such as eye tracking and gesture recognition. With eye tracking, the eye movements are recorded by a so-called “eye tracker” using an integrated camera and then analysed by the system. The identified points of view are then linked to actions such as selecting a field. Mobile eye tracking systems are already being used in HMI interaction to increase the usability and user experience of the respective applications and are also used in the medical field in training, telemedicine and with paralysed patients.
With the help of eye tracking, experts and specialists can see exactly what students, nurses, emergency services or doctors can see on site. Patients who are paralyzed, for example, can communicate with their surroundings and their doctors through the use of eye tracking and the corresponding software. Unlike capacitive 3D gesture control, however, eye tracking requires a well-lit room, since the eye tracker cannot always detect clearly in a dark environment.
In addition to eye tracking, there is also the option of input through gesture recognition using a camera. The camera-based system can recognize simple gestures such as swipe or zoom. If the surgeon needs an X-ray image during an operation, the desired image can be called up without delay by making a hand movement in front of the display. In addition, the risk of contamination is also reduced since there is no need to touch the display. However, this method faces the same trade-offs as the camera based eye tracking solution.
Gesture control using capacitive sensors
But how does capacitive gesture control work? The functional principle is similar to a PCAP system, only with an increased range. The challenge here is to detect the tiny changes in capacitance with low noise. To meet this need, the semiconductor manufacturer Microchip offers GestIC® technology, with which changes in capacitance <1fF (10-15 F) can be detected. The technology is available in three different versions: version 1 (detection of gestures and 3D position), version 2 (cheaper, but only supports gesture recognition) and version 3 with an extended temperature range and certifications, e.g. for automotive applications. With this technology, gesture recognition can be achieved at a distance of up to 20 cm. Version 3 can also be combined with a conventional 2D PCAP, so that simultaneous 2D and 3D operation is possible. This facilitates a large number of new operating concepts for the medical hygiene sector.
DATA MODUL has developed a controller board based on GestIC® technology that combines this 2D PCAP functionality with 3D gesture control (GestIC®). In this PCBA, 2D PCAP Touch and 3D Gesture data acquisitions are synchronised in time to enable 2D and 3D input. In addition to its existing 2D electrode matrix, the PCAP sensor has four additional receiving electrodes for 3D gesture control. These electrodes are arranged like a frame in the periphery of the 2D electrodes. The arrangement is named after the four cardinal directions: north, east, south and west. The add-on “3D gesture control” hardly adds any additional costs to the PCAP system and the 3D gesture control can be deactivated if required.
The advantages of capacitive gesture control over optical and acoustic input systems are clearly their independence from external influences such as light and noise, their low power consumption and their relatively low added cost. In addition, the sensor is easy to integrate into the existing system without the need for additional modifications, such as an opening for a camera.
Especially in areas with higher hygiene requirements, such as hospitals, contactless operating methods in combination with conventional 2D input systems are safe, efficient and future-oriented solutions that are already being increasingly implemented. This is also reflected in the increasing demand for high-quality monitor solutions that are equipped with other technology/features, such as RFID or NFC, as well as the associated software. The combination of classic PCAP technology and DATA MODUL’s 3D gesture control offers a viable alternative to conventional input methods, especially with regard to hygiene.