Sensory functionalisation of materials

In modern industrial applications, there is a growing need to measure mechanical and dynamic state variables directly in the component or material rather than deriving them using discrete, retrofitted sensors. Traditional sensor concepts often require additional housings, mechanical couplings or protective measures, which increases system complexity and interfaces. The sensing materials presented therefore take an integrative approach: the sensor technology is functionally embedded in an elastomer and the material itself takes on the role of the sensor.

Force measurement is carried out via a measuring cell that is completely vulcanised into the elastomeric base material. The underlying operating principle is based on the change in an electrical field parameter as a result of mechanical deformation. The sensor element uses an integrated multi-layer architecture in which mechanically induced structural changes are converted into a proportional change in an electrical output signal. When the material is loaded, the elastic deformation leads to a geometric change in the internal structure. This causes a proportional change in the electrical parameter, which is evaluated as a measurement signal.

The measuring principle is particularly suitable for flat and distributed loads, as the force is not applied at a single point but is distributed evenly across the entire sensor element. The low height of the integrated measuring structure allows a high degree of freedom in the design of the sensing material in terms of geometry, dimensions and measurable load range.

In addition to force measurement, the sensing material is equipped with inertial sensor technology. An integrated acceleration sensor detects linear accelerations and enables the detection of vibrations, oscillations and shock events. The signals obtained from this provide valuable information about dynamic loads, operating conditions or unwanted vibration excitation.

Optionally, a gyroscope sensor can also be integrated to measure angular velocities and thus provide information about the inclination, rotation and spatial orientation of the sensing material. The combination of acceleration and rotation rate sensors enables a comprehensive description of the inertial state. This allows both static and dynamic movements to be recorded, such as tilts, rotational movements or high-frequency vibrations.

Vulcanised sensor integration in elastomer

A key technical feature of the sensing material is the complete vulcanisation of the sensor technology into the elastomer. The measuring cell, the acceleration sensor, the gyroscope sensor and the associated electronics are permanently embedded in the elastomeric matrix. This creates a monolithic, closed structure without open sensor elements or exposed conductor tracks. The electrical connection to the customer’s evaluation electronics can be made either via an integrated plug or an integrated cable (see Figure 2). An integrated cable allows a high IP protection class to be achieved.

This design ensures a defined and reproducible mechanical coupling between the material and the sensor technology. At the same time, the elastomer acts as a damping element and reliably protects the sensors from moisture, dirt and mechanical overload. This makes the sensing material waterproof, insensitive to environmental influences and easy to clean. Vulcanised sensors offer significant advantages over discrete sensor elements. Complete encapsulation ensures high long-term stability, as corrosion, contamination or mechanical wear are eliminated.

In addition, the elastomer-based embedding allows targeted damping of vibrations and shock loads, which improves both the service life of the sensor technology and the quality of the measurement signals. Maintenance and cleaning costs are significantly reduced, which is particularly relevant for applications with high hygienic or environmental requirements.

The measurement data from force, acceleration, and gyroscope sensors are processed internally and provided via a digital interface. This standardized interface simplifies integration into existing control and evaluation systems and enables the synchronous acquisition of multiple measured variables.

Examples of applications for sensing materials

The sensing material is suitable for a wide range of industrial applications. One example is load measurement in commercial vehicles such as lorries or tractors. Here, the elastomer can be used as a load-bearing element that detects the applied load. At the same time, the elastomer acts as a mechanical damper that reduces vibrations from driving and protects the sensor technology from water, dirt and mechanical damage.

Another example of its use is in a tamper mat for espresso preparation. In this application, the sensing material ensures that the coffee powder is always pressed with the same force. Regardless of the operator, this achieves uniform compression, resulting in consistent extraction and reproducible taste.

A third example is a damping element that measures vibrations in addition to its primary mechanical function. The combination of damping and sensor technology allows vibration conditions to be detected directly in the component without the need to install additional sensors.

Customised design and expandability

The sensing material can be highly customised. Geometry, elastomer hardness, force measurement range, sensor configuration and additional features can be adapted to the respective application. This allows tailor-made solutions to be realised that combine mechanical function and sensor technology in a single component.

The sensing material presented here demonstrates how the consistent integration of force sensors, acceleration sensors and gyroscope sensors into an elastomer can result in robust, long-term stable and cleanable sensor systems. The vulcanised design enables close coupling of material and sensor technology and opens up new possibilities for customer-specific, integrated measurement solutions in industrial sensor and measurement technology.

Autor:
Robin Ellinger
Produktmanager bei APSP, Ingenieur