The Innovations- and Technologiezentrum binder ITZ, based in Bad Rappenau, develops new technologies and products for Franz Binder GmbH & Co. Elektrische Bauelemente KG (Neckarsulm). Based on our expertise in chemistry, electronics, physics, and process development, we specialize in applying printable electronic components with the highest precision directly onto 3D surfaces, achieving a seamless integration of functionality and design. Our strength lies in providing customized solutions for a wide range of geometries and substrates. As a pioneer in key printed electronics technologies such as sensors, electroluminescence, heating elements, and fine conductive traces, we functionalize virtually any surface geometry.
In addition, the increasing demand for printed force sensors, in particular force sensing resistors (FSR), emphasises their versatility. It ranges from installation on robot fingertips to sensitive touch sensors for vehicle information systems. FSRs, which are characterised by a polymer thick film (PTF) design, exhibit a decrease in resistance as the force applied to the affected area increases. Optimised for touch control of electronic devices, FSRs have similar properties to load cells and strain gauges. This makes them sought-after components in various industries.
Expertise in force sensing resistors (FSRs)
FSR (Force-Sensitive Resistor) is a type of sensor that changes its resistance when a force is applied. As the applied force increases, the sensor's resistance decreases, allowing for the detection of pressure, compression, and weight. In the context of printed electronics, this refers to a conductive layer whose electrical conductivity changes under force—for example, a printed carbon/graphite layer that is pressed against an adjacent silver electrode layer. The resistance change in an FSR can be measured using appropriate circuits, such as a voltage divider or a Wheatstone bridge configuration. By determining the resistance, the magnitude of the applied force can be quantified. Utilizing this property, FSR sensors enable precise and responsive interaction with electronic systems, making them particularly well-suited for use as a Human-Machine Interface (HMI). While they are not among the most precise sensors, FSRs offer an excellent price-performance ratio for most touch-sensitive applications.
Flexible sensor manufacturing
The screen printing process is used at binder for the high-quality production of FSR sensors. Due to the very homogeneous deposition of conductive pastes in the screen printing process, very finely distributed and interconnected silver electrodes are deposited on one side of a PET substrate. The other side of the sensor contains carbon paste as the active material, which is also printed on a PET substrate. A plastic spacer is used in between. The idea behind this is to work with cost-effective materials and achieve the best possible result. The type of spacer also plays a decisive role in the operation of the sensor. It separates the two layers and its thickness determines the strength of the measured force. This can therefore be customised..
The flexible substrate used for the FSR sensor offers the necessary elasticity to be integrated into any application and on any surface. The round shape can be easily customised depending on the application.
The electronics of the sensor
In addition to printing the functional layers of the FSR, binder also offers the development and series production of the evaluation electronics according to customer requirements. The FSR's shunt mode proved to be an efficient solution for detecting force or pressure. Conventional electronic solutions are then used to convert these pulses into user-specific data that can be read out and further processed.