Membrane Sensors in Medical Technology

Sensory components for the medical technology are deployed in numerous applications to measure and for the control of position and movement sensing. Metallux AG, near Stuttgart, supplies the medical industry for many years now with standard and customised products, amongst them various MetaPot Membrane Sensors in linear and rotative options. Membrane sensors feature amongst others proven safety, precision, impermeability and reliability, essential criteria in medical technology. Furthermore they offer an extremely high life time.

Design and functionality of the membrane sensor

Membrane sensors consist of a thin foil with a high resistive print as well as a collector foil with a low resistive collector print. Substrate and foil are separated by a spacer. A mechanical pressure piece ensures contact with the resistor layer and the collector. The wiper system of the classical potentiometer is thereby replaced with the collector foil and the pressure piece. Thus, as with the conventional potentiometer, the respective location dependent voltage can be tapped. Wear and tear on the resistive layer is therefore excluded.

So far, membrane sensors were designed as a foil-foil technology and feature with their extreme flat design of less than 2mm. Sole disadvantage is the relative large non-linearity of approximately 1%. With the new generation of MetaPot sensors the resistive foil is replaced with a FR4 substrate. As a result the application range of the membrane sensors has been extensively extended. This created many advantages. Resistor pastes can be used which will allow life times of more than 25 million cycles. Also, the usage of FR4 PCB material will permit linearization of the resistive layer. Linearity values between ±0,4% (measuring length 50mm) and ±0,3% (measuring length 500mm) are achievable. This draws the conclusion, that membrane sensors, because of their accuracy, can be compared with the classical Potentiometer-Wiper combination. LinearizedMetaPot Membrane Sensors are available in measurement lengths between 50mm and 500mm.Apart from linear systems linearised rotative systems with a diameter of up to 400mm are also available. This sensoric system takes on more and more significance in the medical technology, be it for diagnosis, operations, therapy or rehabilitation purposes, as following examples show.

Sensors based on the MetaPot membrane technology measure the infinite height adjustment as well as the lowering of operating tables. Linear and rotative sensors allow an optimal operating process for the table as well as the operator. In future this will go so far that part of an operation can be automated thanks to the sensors like positioning of the patient via the table or the making available of auxiliary devices or instruments.

Saline drip pumps are used in hospitals to dispense consistent amounts of medication over a period of time. Important here is the consistent dosage. MetaPot sensors are used as a path measuring device and provide an exact and consistent dosage. The sealed sensor system facilitates easy cleaning of the pump.

Membrane sensors also operate in orthoses (e.g. leg braces). Orthoses support the healing process, are stabilising, immobilising, guiding and correcting of joints.

Rotary sensors in artificial limbs, for example in electrical joint controls, are responsible for the exact position of the joint. High life time is here of importance.

Exact positioning of dental chairs (seat position, position of head and leg supports) or in hospital beds are regulated by linear and rotary sensors which apart from a high precision demand need to satisfy the high hygienic requirements, especially with hospital beds.

Sensors in joysticks control speed and direction of wheelchairs. Joysticks do not only allow for light manoeuvring but also are through their soft feeling(haptic) easy to steer and drive. All those characteristics are achieved with the help of our membrane sensors, linear and rotative.

All those examples show our MetaPot membrane sensors in numerous applications in the medical technology. Compared to other systems our MetaPot membrane technology excels with a very flat design, easy installation possibilities together with a temperature range of -40°C to +85°C; safety, precision, leak tightness and reliability are utmost in the spotlight.

MetaPot Membrane Sensors are hermetically sealed, offering protection against environmental influences like dirt, dust and humidity. Apart from the connection, all requirements to IP67 are complied with.

Metallux:

Metallux AG is a high-performance manufacturer of electronic components in thick-film technology. The Swabian high-tech company has a broad spectrum of services and besides its standard range of pressure, position, angle and film sensors, high-voltage and power resistors, it also offers customer-specific complete solutions through to the packaging of potentiometers and joysticks. An established customer orientation provides suitable ideas and solutions for satisfied customers. Innovative products, a variety of patents and many years of experience - numerous well-known customers from the automotive, electrostatics, medical and industrial electronics and sensor technology industries have been served for over 26 years by the head office situated since November 2011 in Leutenbach-Nellmersbach near Stuttgart, Germany.