Sensor+Test 2018

•••2••• Innovationen Extrem schnell und robust: Li-Fi als WLAN-Alternative Li-Fi (Light Fidelity)-Technologie – also die Datenüber- tragung durch Licht – könnte sich im industriellen Umfeld zu einer echten Alternative zu dem störanfäl- ligen und vergleichsweise langsamen WLAN entwi- ckeln. „Li-Fi nutzt das weltweit nicht regulierte Spek- trum des Lichts“, erläutert Dr. Alexander Noack, Chefentwickler am Fraunhofer IPMS. „Die verfügba- re Bandbreite dieses Spektrums ist ausschließlich durch die für die Modulation beziehungsweise Demo- dulation eingesetzten opto-elektronischen Bauele- mente begrenzt und erlaubt enorm hohe Nettoda- tenraten“. Die Echtzeitfähigkeit ist ein weiteres Merkmal des Systems. Alexander Noack: „WLAN rea- lisiert eine paketbasierte und asynchrone Datenüber- tragung.“ Li-Fi hingegen versendet Daten kontinuier- lich in einem Strom. Anwendungen, in denen Datenberechnung und -übertragung ein vorbestimm- tes Zeitlimit nicht überschreiten dürfen, können mit Li-Fi betrieben werden. Dabei lassen sich mehrere Datenlinks im Raummultiplexverfahren parallel auf- gebauen, ohne dass Interferenzen zwischen den ein- zelnen Datenlinks bestehen. Dies ermöglicht eine störungssichere Industrieumgebung und eine sehr hohe Dichte von Datenübertragungszellen. Li-Fi- funktioniert allerdings nur, wenn die Sichtachse zwi- schen Sender und Empfänger frei ist. Mit Blick auf Datensicherheit ist dies aber auch ein großer Vorteil: Daten lassen sich so von außen nicht abhören. Solving networked sensors’ energy problems Project ZEPOWEL: research scientists develop extremely energy-efficient and modular hardware T he Internet of Things (IoT) is growing steadily. An enor- mous number of networked nodes collecting, evaluating and converging data in a network is therfore already necessary today. The problem: The energy con- sumption of the nodes is enor- mous. The Fraunhofer-Gesells- chaft wants to change that. In its “Towards Zero Power Elec- tronics” (ZEPOWEL) lighthouse project, a hardware solution is to be developed that is both holistic and extremely energy-efficient. In a following step, networked sen- sors could even work with com- plete self-sufficiency. Fraunhofer uses two levers: First- ly, the nodes themselves are to consume significantly less ener- gy, and secondly, energy savings are to be achieved at the systemic level. This means that commu- nication with other systems will also save energy. “We want to create the technological platform for a comprehensive IoT applica- tion,” explains Erik Jung, project team member at the Fraunhofer Institute for Reliability and Micro- integration IZM. New technolo- gies are being developed in the lighthouse project, such as an ul- tra-low-power wake-up receiver, which ensures that a sensor node does not have to transmit data continually, but rather “awakens” at a certain threshold or through an authenticated request from outside. The module developed in the project is expected to be 1000 times more efficient than existing standard radio solutions. The receiver responds only to au- thorized and cryptographically secured signals that are actually relevant for it. In this way, the sensor node can remain in stand- by mode with minimal power con- sumption and be activated imme- diately by the WakeUp receiver as necessary. In addition, the pro- ject is aiming at a unique sensor innovation: an air quality sensor is intended to be coupled with a micro-pump. The pump will then serve as a measuring amplifier by greatly increasing the amount of supplied air. If this attempt is suc- cessful, the result will be a sensor that can be built with much less intrinsic sensitivity, while at the same time providing data that is far more accurate. Whereas to- day’s sensors can deliver 5000 measurements at a power of 1250 microwatts per second, the devel- oped sensor is expected to deliver twice as many readings per sec- ond with a power of less than 10 microwatts. Modular approach Not only is the collection and transmitting of data to be opti- mized, but also the energy bal- ance of the nodes themselves. Therefore, a broadband harvester is to be developed, a kind of har- vester for ambient energy. The ZEPOWEL lighthouse project has also set itself the goal of not de- veloping any purely application- specific nodes, but instead a mod- ular approach based on the plug and play principle. “We offer a module for many applications: it’s a plug-in system, like with Lego blocks. Click – and it works,” ex- plains Erik Jung. Power amplifiers in radio nodes for targeted data transmission for 5G Photo: Fraunhofer IAF Highly sensitive gas sensors New devices detect toxic and non-toxic gas molecules at room temperature A team from the Faculty of Phys- ics of Lomonosov Moscow State University suggested using po- rous silicon nanowire arrays in highly sensitive gas sensors. These devices will be able to de- tect the presence of toxic and non-toxic gas molecules in the air at room temperature. Taking into account high levels of environmental pollution in the modern world, it is important to develop new sensitive devic- es able to identify molecules in gas phase accurately and selec- tively. This is true both for toxic and non-toxic gases. However, the majority of modern gas sen- sors only work at high tempera- tures which limits the scope of their application. Therefore the development of reusable highly sensitive gas detectors working at room temperatures is an im- portant area of modern physics development. The scientists from MSU suggested using porous silicon nanowire arrays as sensi- tive elements of such detectors. They can be obtained by means of a cheap method of the metal- assisted chemical etching. It is based on selective chemical etch- ing, i.e. partial removal of surface layer from a bulk crystalline sili- con with the use of metal nano- particles as a catalyst. Moreover, the procedure is quite quick: at least 100 elements can be pro- duced in a lab within just one hour. The authors have shown that such porous nanowires have huge specific surface area due to which their physical and chemical properties are extremely sensi- tive to molecular environment. Principle of the operation of the sensor based on porous silicon nanowire arrays Photo: Liubov Osminkina