What is the flexible pressure sensor of sensor technology?
Sensor technology is an important driving force for the continuous development of robotics technology. With the development of robotics technology, facing more and more special signals and special environments, higher requirements are placed on various sensors. At the same time, it is hoped that sensors can also be transparent, Flexible, stretchable, free to bend and even fold, easy to carry, wearable, etc. With the development of flexible matrix materials, flexible sensors that meet the above-mentioned trend characteristics have emerged on this basis.
As the "veteran" of the sensor industry, pressure sensors are an important component in its field. The flexible pressure sensor has excellent mechanical and electrical characteristics, such as high flexibility, high sensitivity, high resolution and fast response, so it has a wide range of applications.
According to the working mechanism of pressure sensors, they can be roughly divided into the following categories: piezoresistive, capacitive, piezoelectric and other types of pressure sensors.
Piezoresistive flexible pressure sensor
Piezoresistive flexible pressure sensor The sensor based on the piezoresistive effect will deform the active material under the action of external force, and indirectly change the distribution and contact state of the internal conductive material, resulting in a regular change in the resistance of the active material.
The common sensing mechanism and representative device of piezoresistive sensors
Compared with capacitive and piezoelectric pressure sensors, they do not require complex sensor structures, have lower power consumption, a wide range of test pressures, and simple manufacturing processes. They can be used for medical inspections, seal inspections, physical exercises, etc. There are already some commercial products on the market, such as smart clothes, which can monitor the heartbeat through resistance changes to prevent heart disease and other diseases.
Kim type piezoresistive pressure sensor
Kim et al. proposed a piezoresistive pressure sensor based on PDMS matrix. This pressure sensor has high sensitivity,
The structure is simple and has a wearable function. This sensor exhibits good sensing performance, with a sensitivity of up to 0.3 kPa-1 and a response time of 162 ms, which ensures that it can be used to detect the motion of human joints.
Capacitive flexible pressure sensor
Capacitive flexible pressure sensor is a device based on the principle of parallel plate capacitance, which has the advantages of high sensitivity, fast response, and wide dynamic range. Its working mechanism is to change the capacitance of the sensor by changing the distance between the plate capacitors when an external force is applied. The conduction mechanism and a schematic diagram of a representative device are as follows.
Common sensing mechanisms and representative devices of capacitive sensors
In recent years, the development of precision capacitive sensors has attracted a lot of attention. Different researches have been done on the design, characteristics, operation and possible applications of this device.
Kentaro Noda et al. proposed a flexible capacitive sensor that can detect three-dimensional
pressure. The sensor can detect positive force or shear force. When the sensor is stretched or compressed, the output status of the sensor will be changed. This sensor is composed of 4 pressure sensing units and a stretch sensing unit with conductive liquid. The sensor can not only detect the pressure but also display the current sensor. In the case of being stretched, the strength of the sensor can be known from the capacitance, and the stretch of the sensor can be known from the resistance, as shown, so the stretched part of the sensor can be compensated, so it can be applied to the stretching with different actions Or compressed robot joints [4].
Kentaro capacitive flexible sensor
Piezoelectric flexible pressure sensor
When certain dielectric materials are subjected to external forces in a certain direction, their internal polarization will occur, resulting in opposite charges appearing on its two opposite surfaces, or potential differences. This phenomenon is called the forward/inverse piezoelectric effect. A type of sensor developed based on the piezoelectric effect of a dielectric is called a piezoelectric sensor.
Common conduction mechanism and representative device of piezoelectric sensor
Piezoelectric materials can generate electricity when deformed, and vice versa. This dual function of piezoelectric materials provides a foundation for more and more applications, especially wearable or implantable systems. Specific examples include sustainable power supplies in consumer electronics and biomedical devices such as sensors for measuring blood pressure. The development of material science, mechanics and manufacturing has made it possible to construct ultra-thin, flexible and mechanically scalable piezoelectric devices.
Chen et al. proposed a new type of static measurement pressure sensor with nanowire/Graphene heterostructure. Compared with traditional pure nanowire or Graphene-based piezoelectric pressure sensors, this device can measure static pressure with a sensitivity of 9.4×103kPa and a response time as low as 57 ms. The pressure sensor has a very broad application potential in electronic skin and wearable devices.
New static measurement pressure sensor
In the past ten years, research on flexible wearable sensor devices has grown rapidly. With the vigorous development of smart robots and wearable electronic devices, research on various new devices based on flexible pressure sensors that conform to arbitrary curves and surfaces is also proceeding rapidly. In the future, flexible sensing technology will play an increasingly important role.
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