Plastics in sensor technology

Modern sensor technology is an indispensable component of numerous future technologies. Whether in industrial automation, automotive engineering, medical technology or in aerospace: precise measurements form the basis for safety, efficiency and innovation. Sensors continuously supply data that monitor processes, control machines or record health conditions. For these highly sensitive systems to work reliably, it is not only the electronic circuit and software that matter, but also, to a decisive extent, the materials used.

They protect the sensors from external influences, ensure interference-free signal transmission and are what make the necessary precision possible in the first place. Plastics have proven to be particularly valuable materials in this context. Through their versatility, adaptability and the possibility of being specifically modified, they meet the complex requirements of modern measurement technology. They not only open up classic fields of application, but also create new potential for innovation and miniaturisation.

Requirements for plastics in sensor technology

Sensors must function reliably in the most diverse environments – from sterile operating theatres to humid production halls and aggressive chemical plants. The materials must therefore combine a wide range of properties. Electrical insulation is particularly important so that no interference occurs in signal transmission. Equally crucial is high dimensional stability so that measurements remain precise even under strong temperature fluctuations.

In addition, plastics must be resistant to oils, greases, solvents, cleaning agents and aggressive media. For optical applications, high light transmission is required, while high-performance plastics must also retain their shape at temperatures above 200 °C. In medical technology, biocompatibility is also a central criterion so that the materials can be used in the body without problems. Finally, low weight also plays an essential role, as it enables compact and energy-efficient sensor designs.

If a plastic surface itself is to be detected or measured, the measuring principle used must also be taken into account. Colour, transparency, surface structure and distance can, for example, influence the choice of optical sensors. For reliable measurement, both the properties of the plastic and the specific installation situation should therefore be taken into account.

Commonly used plastics for sensors

Polycarbonate (PC)

Polycarbonate is one of the most widely used plastics in sensor technology, especially when it comes to optical applications. Its high transparency enables almost loss-free light transmission, which is crucial for lenses, covers or light guides.

In addition, PC is extremely impact-resistant, which reliably protects sensitive sensor elements. It also remains dimensionally stable under temperature fluctuations. Typical fields of application are housings for optical sensors, protective covers in automotive engineering or transparent components in medical technology.

Polyetheretherketone (PEEK)

PEEK is a high-performance plastic that works reliably even under extreme conditions. With a continuous service temperature of up to 250 °C, it is suitable for sensors used in engines, turbines or chemical reactors. Its exceptional chemical resistance makes it ideal for environments in which aggressive liquids or gases occur.

PEEK also impresses with extremely high dimensional stability, which is indispensable for precise measurements. In medical technology, PEEK is also used for implantable sensors because it is biocompatible.

Polyamide (PA)

Polyamides are versatile materials that impress with their high mechanical strength and abrasion resistance. In sensor technology, they are often used for mounts, plug connections and housings that require both stability and flexibility.

Since PA absorbs a certain amount of moisture, applications must be carefully assessed – at the same time, this behaviour offers advantages when flexible or vibration-damping properties are required. Particularly in automotive and mechanical engineering sensor technology, PA is widespread due to its robustness.

Polymethyl methacrylate (PMMA)

PMMA, also known as acrylic glass, offers excellent optical quality with high transparency and light transmission of up to 92 %. It is preferably used for optical components that require a clear view or precise light guidance – such as lenses, protective discs or light guides.

PMMA is also UV-resistant and weather-resistant, which means it also works reliably in outdoor sensors. Another advantage is its ease of processing, which enables cost-efficient production of complex parts.

Fluoropolymers (e.g. PTFE, FEP)

Fluoropolymers such as PTFE and FEP are among the most chemically resistant plastics of all. They are virtually inert to most chemicals and also have excellent non-stick and sliding properties. In sensor technology, they are often used as protective layers or insulation, for example in gas and liquid sensors that are exposed to aggressive media.

They are also used in medical technology, as they are biocompatible and can be easily processed under sterilisation. Their high temperature resistance additionally broadens the range of applications, from laboratory applications to industrial high-temperature processes.

Other high-performance plastics

• PPS (polyphenylene sulphide): Offers a combination of high temperature resistance, excellent dimensional stability and chemical resistance. Ideal for precise sensor components in the engine compartment or in aggressive production environments.
• LCP (liquid crystal polymer): Particularly suitable for the miniaturisation of sensor components, as it is extremely dimensionally stable and offers excellent electrical insulation.
• TPU (thermoplastic polyurethane): A flexible and abrasion-resistant plastic that is frequently used as cable sheathing for sensors. TPU protects against mechanical loads but remains elastic in the process.

Comparison of selected plastics

Plastic	Special properties	Typical applications
PC	Transparent, impact-resistant, dimensionally stable	Optical sensors, covers, housings
PEEK	Heat-resistant, chemically resistant, biocompatible	Engine and turbine sensors, implantable sensors
PA	Mechanically strong, abrasion-resistant, flexible	Plug connectors, housings, mounts
PMMA	Very transparent, UV-resistant, weather-resistant	Lenses, light guides, outdoor sensors
PTFE/FEP	Chemically inert, non-stick, temperature-resistant	Protective layers, liquid and gas sensors

Advantages of plastics in measurement technology

Compared with metals, plastics offer a wide range of advantages that make them particularly attractive for use in sensor technology. One of the biggest plus points is the significant reduction in weight. Lighter materials enable more compact designs, lower transport and energy costs and contribute to the miniaturisation of sensor components. In addition, plastics offer enormous design freedom: they can be formed into almost any shape, which means that complex and highly integrated components can also be produced that would be difficult or very cost-intensive to realise with metals.

Another decisive advantage is the possibility of functionalisation. Through targeted additives, plastics can be made electrically conductive, mechanically reinforced or protected against UV radiation. This creates tailor-made materials that are precisely matched to the requirements of a specific sensor application. At the same time, plastics are corrosion-resistant and, unlike metals, require no additional protection against rust or environmental influences. This significantly increases the service life of sensors and reduces maintenance effort and follow-up costs.

Plastics also impress in terms of economic efficiency. They can be processed efficiently, enable fast production cycles and are more cost-effective compared with many metals. This aspect plays a central role, particularly for large quantities such as those occurring in the automotive industry or consumer electronics. Finally, plastics score with their thermal and electrical insulation, which enables safe signal transmission and protects sensitive electronics from external influences. In sum, all these advantages contribute to plastics representing not just an alternative in measurement technology, but the preferred choice in many areas.

Typical applications in practice

• Automotive industry: Sensors for driver assistance systems (radar, camera, ultrasound), exhaust sensors or pressure sensors for tyre pressure monitoring.
• Medical technology: Blood pressure sensors, implant sensors, monitoring systems – here biocompatibility is crucial.
• Industry 4.0: Sensors for condition monitoring of machines, temperature and pressure sensors as well as precise measuring probes for production processes.
• Optical sensor technology: Light sensors, scanners, 3D cameras, laser systems.
• Environmental technology: Sensors for measuring air quality, humidity or flow.

Pressure sensors in plastics processing

For injection moulding and extrusion processes, cavity pressure and melt pressure sensors in particular are used. At high process temperatures, the sensor and surrounding components must be permanently temperature-resistant and dimensionally stable. Piezoresistive melt pressure sensors, for example, are suitable for continuous pressure measurements in injection moulding machines, extruders and hot runner systems.

When selecting a suitable pressure sensor, in addition to the measuring range and temperature, the polymer to be processed, the installation situation and direct contact with the plastic melt must in particular be taken into account.

Which sensor is suitable for plastics processing?

The selection depends on the respective measuring task. Pressure and melt pressure sensors, for example, monitor injection moulding and extrusion processes, temperature sensors control the mould and melt, while optical or inductive sensors can be used for position, presence or process control.

Which sensor is best suited therefore depends on the measuring objective, the process temperature, the distance to the measuring object and the respective ambient conditions.

Future trends: smart materials and hybrid solutions

The further development of sensor technology is increasingly being driven by innovative material solutions. Nano-reinforced plastics, for example, offer improved barrier properties thanks to their modified structure and at the same time higher mechanical strength. Self-healing polymers are also coming more strongly into focus, as they can extend the service life of sensors by independently repairing small cracks or damage.

Another trend is hybrid materials that combine plastics with metals or ceramics and thus unite specific advantages – such as the lightness and formability of plastics with the hardness and thermal conductivity of other materials. At the same time, the importance of sustainable materials is growing. Recyclable high-performance plastics are becoming increasingly relevant, as they not only meet technical requirements but also satisfy rising ecological demands.

These developments show that plastics will also play a key role in sensor technology in the future and will open up new fields of application through intelligent material innovations.

In conclusion

Plastics have decisively shaped sensor technology over the past decades and today enable a wide range of applications that would be inconceivable without their special properties. They are light, versatile and can be specifically modified for special requirements. Their importance ranges from the automotive industry to medical technology and Industry 4.0, where they impress through precision, durability and functionality.

While metals continue to have their justification in certain segments, plastics are in many cases the more efficient, more flexible and more innovative solution. Looking to the future, it is to be expected that new developments such as self-healing polymers, nano-reinforced materials and recyclable high-performance plastics will significantly expand the possible applications once again. The role of plastics in sensor technology thus remains not only stable, but will continue to gain in importance through the combination of technical performance and sustainability.

Which plastic solution is suitable for a sensor application depends in particular on temperature, chemical exposure, electrical requirements, dimensional accuracy and the respective measuring principle. Especially with industrial sensors, the material and sensor technology should therefore be considered together.

FAQ

Which plastics are particularly suitable for high temperatures? PEEK, PPS and fluoropolymers such as PTFE are heat-resistant and retain their properties even at temperatures above 200 °C.

What is the advantage of PMMA in optical sensors? PMMA offers outstanding light transmission and is UV-stable, which makes it ideal for lenses, covers and outdoor applications.

Are plastics permitted in medical technology? Yes, many plastics such as PEEK or certain fluoropolymers are biocompatible and meet the requirements for use in medical technology.

Can plastics exhibit electrical conductivity? Yes, through additives such as carbon fibres or conductive particles, plastics can be electrically modified, for example to dissipate static charges.

What role do plastics play in the miniaturisation of sensors? Thanks to their high freedom of form and stability, plastics enable the production of delicate and complex components that are indispensable for compact sensors.

Which pressure sensors are suitable for use in the plastics industry?

For plastics processing, cavity pressure sensors and melt pressure sensors, among others, are used. They are used, for example, in injection moulding, in extrusion plants or in hot runner systems. Which version is suitable depends above all on the required measuring range, the processing temperature, the material and the respective installation situation.

Which sensors are suitable for plastics processing?

That depends on the respective measuring task. Pressure sensors are suitable for monitoring mould and melt pressure, temperature sensors for controlling the mould and plastic melt. Optical, inductive or capacitive sensors can, for example, be used for presence, position or distance measurements.

Can inductive sensors detect through plastic?

Yes. Inductive sensors detect metallic objects and can also register these through non-metallic materials such as plastic. The prerequisite is that the metallic target is still within the permissible switching distance of the sensor. The sensor does not detect the plastic itself, but the metal behind it.