Deliverables
Summary:
Optoelectronics measuring modules for measuring luminescence intensity with fiber-optic microsensors have been developed for laboratory and field applications. The instruments use an amplitude modulation technique to evaluate the luminescence intensity from the connected sensor fiber, and delivers a voltage signal that is proportional to the analyte dependent luminescent intensity at the sensor fiber tip. Modules for fiber-optic microsensors measuring oxygen, pH, carbon dioxide, temperature and natural luminescence can easily be realised by the appropriate choice and installation of optical excitation and emission filters.
Summary:
An simple fiber-optic surface detection system has been developed. The system measures the increasing amount of amplitude modulated backscattered NIR light via a simple tapered optical fiber that approaches a surface or optical boundary where a refractive index mismatch occurs.
With this system, a surface detection with a spatial resolution of <50 (micro)m is possible. By combining the tapered fiber from the surface detection system with another micrsensor, it is possible to realise autonomous profiling and detection at high spatial resolution. The detection principle works for all interfaces, where a refractive index mismatch, and therefore a shift in scattering properties occurs.
Summary:
A laboratory type instrument has been built up for measurement of AC-signals in the frequency range 0.1 Hz to 5 kHz intended for the use of optical absorption measurement. The instrument thus can replace multiple 'Lock-In Amplifiers' in laboratory measurement set-ups or can be used in various technical fields for prototyping purposes.
Applications range from modulated optical measurements (optical absorption, fluorescence, phosphorescence) for sensors to reflection measurements and electrical impedance measurements using modulated signals.
The number of channels is configurable from 2 up to 32, independently programmable in frequency, thus allowing for frequency multiplexed, simultaneous measurements of all signals.
The instrument has two interfaces, a standard RS232 connection (e.g. to a personnel computer) and a field-bus type interface (CAN). Key features are:
- high resolution of up to 18 bits
- channel separation > 80 dB
- high suppression of interfering noise from mains and harmonics
- high dynamic range
- fully digital signal processed for excellent stability
Application fields cover:
- optical parameter measurement,
- electrical parameter measurement,
- optoelectronic sensing,
- luminescence sensing,
- transducer readout
The instrument is at a pre-product stage and requires only a little development for exploitation in laboratory equipment industry.
Summary:
A laboratory type instrument has been built up for measurement of AC-signals, both in amplitude and phase (i.e. a 'vector'- measurement) in the frequency range from 1 Hz to 200kHz. The instrument thus can replace multiple 'Lock-In Amplifiers' in laboratory measurement set-ups or can be used in various technical fields for prototyping purposes.
Applications range from modulated optical measurements (optical absorption, fluorescence magnitude and lifetime, photophosphorescence magnitude and lifetime) sensors to electrical impedance measurements using modulated signals up to 200 kHz.
The instrument has 2 channels, independently programmable in frequency.
It can be operated via two interfaces, a standard RS232 connection (e.g. to a personnel computer) and a field-bus type interface (CAN)
Key features are:
- high resolution of up to 18 bits in amplitude
- high resolution of up to 18 bits in phase (i.e. 0.001 degrees or 2e-5 radians)
- high resolution in time delay of up to 20 picoseconds
- channel separation >80 dB
- high suppression of interfering noise from mains and harmonics
- high dynamic range
- fully digital signal processed for excellent stability in precision phase measurements
Application fields cover:
- optical measurements, e.g.. Absorption or reflection type sensors
- electrical parameter measurement, e.g.. Capacitive or inductive sensors
- optoelectronic sensing, eg gyroscoped or laser ranging
- luminescence lifetime sensing,
- high resolution LVDT or RVDT transducer readout
The instrument is at a pre-product stage and requires only a little development for exploitation in laboratory equipment industry.
Summary:
A portable measuring system has been developed for laboratory and field application of fiber-optic microsensors for physical-chemical variables like oxygen, pH, carbo dioxide, temperature, and chlorophyll. The system consists of a modulated LED excitation source and photomultiplyer detector connected via an optical system. The configuration of the instrument can easily be adapted for a specific microsensor type by installation of appropriate optical excitation and detection filters. The meter uses a phase modulation technique to evaluate the analyse dependent shift in the luminescense intensity and lifetime signal from the sensor tip. System configuration, calibration and data acquisition are controlled via an instrument micro-controller that interfaces to a PC. Special software for instrument control and data acquisition on a PC has been developed. In its present form, the instrument control and data acquisition on a PC has been developed.
The instrument has been used for measuring oxygen distributions in heterogeneous sediment and biofilm samples in applications. A prototype of the instrument is currently tested on a cruise with the research vessel Polarstern as part of a collaboration with the Alfred Wegner Institute for Polar Research, Bremerhaven, Germany.
Summary:
A miniaturized measurement module has built up for measurement of AC-signals, both in amplitude and phase (i.e. a 'vector' measurement) in the frequency range from 1 Hz to 40 kHz. The instrument thus can replace 'Lock-In'-type structures for sensing applications or sensor readout electronics. Applications range from modulated optical measurements (optical absorption, fluorescence magnitude and lifetime, phosphorescence magnitude and lifetime) for sensors to electrical impedance measurements using modulated signals up to 40 kHz. The instrument has 1 channel, programmable in frequency. The module can be operated via two interfaces, a standard RS232 connection (e.g. to a personal computer) and an analogue interface (2 output channels 0-2.5 Volts). Key features are: - high resolution of up to 16 bits in amplitude - high resolution of up to 16 bits in phase (i.e. 0.004 degrees or 8e-5 radians) - high resolution in time delay of up to 200 picoseconds - high suppression of interfering noise from mains and harmonics - high dynamic range - fully digital signal processed for excellent stability in precision phase measurements Application fields cover: - optical measurements, e.g. absorption of reflection type sensors - electrical parameter measurement, e.g. capacitive or inductive sensors - optoelectronic sensing, e.g. gyroscopes or laser ranging - luminescence lifetime sensing. - high resolution LVDT or RVDT transducer readout. The module is at a pre-product stage and requires only little development for exploitation in laboratory equipment industry.
A multichannel instrument for the instrument for the simultaneous use of up to 8 fiber-optic microsensors in the laboratory has been developed. The measuring system is based on a similar detection principle for luminescence intensity and lifetime measurements as has been realised in the single channel instrument MICROX I, the microoptode array is equipped with a fiber-optic switch, or, alternatively, an array of fiber-optic couplers, that enables the instrument to continuously scan the measuring signals from the connected sensors. System configuration, calibration and data acquisition are controlled via an instrument micro-controller that interfaces to a PC, Special software for instrument control and data acquisition on a PC has been developed.
Summary:
A simple microscale sensor for nitrate plus nitrate has been developed. It is based on a tapered sensor casing with ion-permeable membrane in the 20-100 thick tip, Nitrate and nitrate diffuse through the tip and into a dense mass of bacteria that reduce the nitrate and nitrate to nitrous oxide which is subsequently detected by a built-in electrochemical nitrous oxide microsensor. Usually nitrate is present in much larger concentrations than nitrate, and we thus usually name the sensor a nitrate biosensor. The sensitivity of the sensor can be tailored to any specific needs by applying a voltage between the sensor and the analyzed liquid, as nitrate ions then can be electrically attracted to repulsed from the sensor. By use of such polarization sensors may detect nitrate down to 0.1 M. Except for nitrous oxide , nothing interferes with the determination of nitrate plus nitrite, and the nitrous oxide interference can easily be corrected for by changing the electrode negatively, thereby hindering the entrance of the negative ions. The response time (90%) is usually better than 1 min. The lifetime is at present a few weeks, but it should be possible to improve this to a few months. The sensor should have a large market in waste water treatment and in analytical laboratories.
Summary:
A simple and inexpensive microscale (20-150 m tip) sensor for flow and diffusivity has been developed. It is based on diffusion or advectional transport of a tracer molecule away from a sensor tip, where a transducer continuously monitors the concentration of this tracer at the surface of the sensor. The sensor is ideal for measuring flow in narrow tubes or diffusivity of the tracer in tissue or environmental samples. It offers resolution of flow over a wider dynamic range than any previously described method (10 m - 10cm per second) and quantifies diffusivity in any relevant range. It is much simple and cheaper method for determination of flow than the often used laser doppler methods, and it offers higher resolution. A similar resolution can be obtained by NMR, but such analysis is extremely costly and complicated. It is not suitable for analysis of flow gradients where the sensors shaft if positioned in the flow gradient, as turbulence caused by the shaft may affect the results. Used for diffusivity, the sensor has no alternative methods to compare with, as diffusivity until now only could be estimated at a macroscale by sensors (electrical conductivity)
Summary:
An optical CO2-microsensor, based on the Severinghaus principle, was developed. The sensor sensitivity was optimized to the low CO2 levels which occur in natural waters. The dimensions of the sensor allows measurements with high spatial resolution. First characterization measurements shows a measuring and storage stability that is, at least, comparable with electrochemical pCO2 microsensors.
A microscale biosensor for determination of dissolved chemical species (electron donors) that can be oxidized by specific groups of micro-organisms has been developed. It consists of another casing with a tip membrane of 10-100 µm in diameter. Behind the membrane a dense mass of micro-organisms oxidize material entering through the membrane using oxygen from an internal gas reservoir. An oxygen microsensor is positioned within the biosensor where it monitors the oxygen gradient which changes along with changes in the concentration (supply) of electron donor. The sensor has until now only been used with methane oxidizing bacteria, where it has been able to monitor methane concentrations from about 2 µm and up to saturation (1mM). Used with a heterotrophic micro-organisms and a dialysis membrane the sensor can, however, also be used to measure dissolved organic in anaerobic environments. The idea of having an oxic microenvironment with the sensor is new and should result in a new result in a new type of "BOD" sensor for use in waste water treatment, where more reliable sensors for this purpose are in high demand.
Summary:
A fiber-optic pH-microsensor for fine scale measurements of pH in the marine environment and other aquatic systems were developed. The sensor sensitivity was optimized to the pH of seawater.
Summary:
Three different concepts for fiber-optic temperature microsensors were developed. The construction of the sensors need different amounts of costs and experiences. All sensors allow measurements with high spatial resolution. The thermal resolution depends on the construction of the microsensor tip and the shielding of the indicator chemistry against interference.
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