New sensors with non-destructive and label-free measurements
The aim of the research project is to develop a miniaturised sensor platform that utilises the surface plasmon resonance (SPR) principle, whereby it is intended that it should also be capable of recognising changes in the chemical composition of various fluids both on- and inline. Because of its advantages in regards to non-destructive and label-free measurements and its extreme sensitivity, SPR technology has so far been used very successfully at the laboratory scale, for example in bioanalysis and drug screening. The developers now want to transfer these benefits to ultra-compact sensors.
The focus is on two main research areas: firstly, the miniaturisation and integration of measurement technology in an ultra-compact unit that allows not only cost-effective mass production but also user-friendly handling by untrained personnel; secondly, the development of an ultra-thin, chemically sensitive layer that is only a few nanometres thick and which also has multiple sensor spots across an area of just a few square millimetres. Using pattern recognition analogous to an artificial nose, it is intended that this smart sensor shall reliably monitor the ageing condition of transformer insulating oils in real time.
Requirements for launching the project defined
In a first step, the researchers have defined the requirements for the sensor and from these derived and determined the later specifications. This was necessary to ensure that the individual working groups can develop independently of one another. The results will be set out in a table with the parameters and tolerances of the materials. In particular it will be ensured that sufficient freedom is provided for the individual work packages and that only parameters are defined precisely that require several working groups. A further elementary component is the design of a reference measurement station. This replicates the basic structure of the sensor at the laboratory scale and will be used in the following development stages both as a reference and a test platform for individual components.
The illustration below shows the technical work schedule for μ-SPIN. Following the joint conception and specification analysis, a reference system will be created in accordance with the requirements at a laboratory scale, which will serve as an experimental and test platform for the subsequent working steps. The miniaturisation begins with the creation of a virtual sensor model and its simulation. For the further progress, the software and electronics as well as the microfluidics will be developed in parallel. The receptor for the analyte detection will be designed independently of these steps. In the final step, the results of the individual steps will be incorporated into a miniaturised sensor system and undergo detailed practical testing in order to make comparisons with existing analysis methods.
The chemoreceptive layer consists of a thin film that ranges in thickness between a few nanometres and micrometres and which is applied to a thin metal layer. This film can selectively bind specific constituents of the material being analysed, thus changing its properties. This causes a localised change in the refractive index in the immediate vicinity of the metal layer. The SPR system reacts extremely sensitively to the smallest changes in the refractive index. The layer is arranged by means of self-organisation and through implementing selective molecular recognition motifs so that regions of different selectivity are available on the surface. By using pattern recognition, a two-dimensional readout of the signal change then enables qualitative changes in the analyte to be determined.
Receptors for precisely analysing the data
In order to analyse the data with sufficient accuracy, the researchers are working with different receptors that are categorised in three stages according to the traffic light principle. The receptors work in a manner comparable to the human tongue. This has only six different taste receptors but can distinguish between an almost infinite number of flavours. If the tongue were only capable of differentiating between ten intensity levels per basic flavour, the total number of distinct activation patterns would amount to 106 = 1,000,000. For the first laboratory samples for the SPR sensor it is planned to use four receptors that will be categorised in three stages according to the traffic light principle. This results in 34 = 81 distinguishable states for the medium being investigated. If two more receptors are added and the state of the receptors is divided into four categories, this already results in 46 = 4,096 different states for the material being analysed. The patterns that can be recognised in this manner will be classified in accordance with the condition of the transformers in field trials, thereby enabling real-time monitoring of the devices.
The milestones at a glance
- Determination of the specifications
- Creation of a reference measurement station (macro sensor)
- Creation of a sensor surface with microfluidics
- Control and signal evaluation of the SPR sensor
- Miniaturised technology carrier
The initial results are expected during 2015.
08/2014 – 08/2017
93053 Regensburg, Germany