It is high time for IR sensor 2.0 – driven by the IoT

The IR sensor is a crucial component in many everyday products, ranging from medical equipment to mobile phones. But the technology is 50 years old and in serious need of an upgrade. The next generation IR sensor 2.0 for IoT will be much thinner than old sensors and cheaper to manufacture.

Today's manufacturing industry is highly dependent on sensors. Whether it is heavy industrial products or smaller consumer products – they are all more or less dependent on well-functioning sensors that control levels, presence, temperatures and pressures. Even in medical technology, sensors are used, for example, to measure EEG and ECG, to name only two areas of use.

The extensive spread of the IR sensor began in the 1950’s when industries expanded in size and gained a greater degree of automation. In this process, the sensor came to play a major role in the development of the manufacturing industry, and so it does still today with the same principle.

Simply described, the sensor is required when you need to record and compile the detection and communication of a particular event. And, as mentioned earlier, the applications are numerous. A sensor designed to trigger alarms is often called the detector, and is usually activated when exceeding limit values, such as high temperature or low pressure. Other types of sensors are photodiodes, cameras, microphones, radar, sonar and pressure sensors.

The new IR sensor 2.0 will be the bridge between the analogue and the digital in an increasingly connected world

In the new connected world that is now emerging, I believe that the new IR sensor has the potential to become the bridge between the analogue and the digital world. And the digitally connected world is growing strongly. Therefore, it is not a bold assumption, that in the near future everything that can be linked up will be connected.

Security and reliability are of course important components in such a process, but if there is a demand and customer benefit in place, it will most likely happen. And as stated earlier, the development is very fast. Only ten years ago, there were very few who could predict how many services would move into smart phones and other consumer electronics. And now there is also a similar development in the area of Internet of Things, where the actual sensors can play an important role.

Small thermopile sensors that measure heat flow open up for new areas of use

The thermopile is a series of series-connected thermo couples that can convert thermal energy into electrical energy. With the help of the new generation of IR sensors, it can also be used for contactless measurement of temperature and heat flow, as well as presence detection. These kinds of sensors can be used to measure the object's temperature or relative temperature differences, and can also measure presence and motion. Thermopiles are the most useful sensor technology for several commercial applications such as smoke and gas detection, motion, absolute temperature measurements, heat measurement and control of heat sensitive parts and plumbing.

However, the size and manufacturing cost of the first generations thermopiles have limited the application areas. New advanced thermopile sensors also measure heat flow and have a time constant describing how fast it reacts to the value change. These are made with nanotechnology in a plastic matrix, and are constructed in three different layers, where the most important layer is thermopile layer.

Conventional horizontal architecture expensive and difficult to manufacture

When the thermopile transforms the energy, an electrical voltage is produced proportional to the applied temperature difference, which makes the thermopile able to read the temperature. With the conventional architecture, the thermocouples are configured horizontally, which limits the design of the sensor and makes a conventional sensor much more difficult to mass-produce, this because a protective metal container is required.

The complete surface of horizontally configured thermopiles cannot be used, nor can the actual “contact mode” be used. Due to the horizontal configuration, conventional sensors need encapsulation to perform contactless measure temperature, and be robust enough for commercial purposes.

Vertical architecture provides several advantages

In a vertical architecture, the hot and cold connection is connected via the thermopile’s thermocouples through nanowires consisting of two different metals. The thermocouples are also vertically positioned. Vertical, or so-called “out-of-plane” configuration requires that the thermocouple’s wires are drawn through the substrate material, coupling them to the surface in so-called “dog bones”. These wires must be extremely thin, which has previously been very difficult to achieve.

Thanks to new technology, where the thermocouple's lead structure is based on nanotechnology, they are more easily mass produced. The advantage of the vertical arrangement of thermocouple conductors – perpendicular to the plan configuration – is that the hot and cold bonds are separated by the substrate thickness, which is also why the structure becomes more robust compared to the very thin silicon membrane of conventional thermostatic sensors.

The object being measured can actually be in contact with the sensor, without the sensor being destroyed. For long-range IR measurements, the next generation sensors can also be equipped with a lens to reduce the field of view and enable measurements of spots. Furthermore, the vertical configuration also allows the thermopile to measure heat flow, which ordinary thermopiles cannot do.

The thermopile layer is the proprietary component of the sensor. The IR absorber layer, the connections between the nanotubes and the protective layer are standard components and processes, and are provided by an external partner. This enables high volume production, low capital and low production costs. The IR absorber layer is there to absorb the IR heat, which the thermopile layer then uses to create a voltage difference. The sensor also includes four surface-mounted "soldering pads" to easily mount the sensor directly to a circuit board.

Robust, power-efficient, easy and inexpensive to produce

The vertical architecture of IR sensor 2.0 makes it possible to manufacture the new sensors out of flexible plastic, instead of fragile ceramics or silicon, which is used in most other IR sensors on the market. The plastic matrix containing the nano-threads makes the sensor very robust and can be moulded according to the customer's wishes. In addition, the sensor can be touched and also used as a (haptic) pushbutton.

The low energy consumption is another important feature. The total cost of a sensor can be divided into three subcategories: raw materials, production and integration. The raw materials or material bill represents a lower limit for the sensor's cost. No matter how efficient the production is or how many sensors are produced, the cost per sensor will not be lower than the cost of the raw materials from which the sensor is made.

In addition to raw materials, the sensor must be manufactured and integrated into the buyer's hardware. Given that these sensors are developed for mass production using conventional circuit board technology, the cost of producing the sensor is low compared with conventional IR sensors. I expect the production cost of a sensor could be up to 1/10 per unit in large volumes, compared to a conventional sensor. Today we stand on the threshold of ushering in IR sensor 2.0; the necessary research and development is done and the concept is proven. All that remains is for the market to detect this new generation's sensor.

In a connected world flooding with data, there will be many opportunities to achieve a safer, more environmentally friendly and a more sustainable society. But to achieve this, it is also important to use the right technology. In such a world, it is time for an IR sensor 2.0.

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