There is a need for inexpensive new instruments that could measure and monitor the concentration of environmentally important chemicals in both water and soil. These instruments have to be easy to use, portable, and capable of prolonged service-free operation. We are interested in developing a range of micromachined chemical sensors that could become the core technology for such instrumentation. These sensors will selectively measure concentration of phosphate, nitrate, lead, and other important nutrients and contaminants. Arrays formed with these sensors could become the basis for a generation of novel and inexpensive hand-held or autonomous chemical monitors.

Fringing electric field selective polymer sensor system

The selectivity of the individual micro sensors will be achieved with novel polymers each bearing binding sites tuned to capture only one specific analyte. The reversible binding between the analyte molecule and a binding site will alter the chemical and physical properties of the polymer. These changes can be detected using the fluorescence or dielectric spectrometry techniques.

Phosphate was chosen to be the target for the development of the first proof of concept polymer-based chemical sensor. At the current stage, we are seeking external funding to allow us to conduct the phosphate sensor feasibility study. Together with our academic collaborators, we are submitting a number of SBIR/STTR proposals to the government agencies. The proposed Phase I work plan aims at investigating the polymer’s binding selectivity for phosphate and optimizing the dielectrometry platform to achieve desired sensitivity.

In recent years a great deal of interest has been focused on wastewater treatment plant design and control strategies which achieve simultaneous nitrification and denitrification in a single reactor. To reliably achieve SNdN, the dissolved oxygen levels must be tightly controlled at very low levels. The instrumentation and control system which can continuously maintain such oxygen level is the major challenge in the design and operation of SNdN systems. We are developing an innovative control technique that uses the concentrations of nitrate and nitrite directly as the primary control variables.

Development of analytical in-situ system for independent low-level nitrate/nitrite measurement in wastewater is the key for realizing the improved SNdN control algorithm. We are evaluating a number of original technologies that may provide such measurement capability. One of these technologies is the atmospheric pressure ion mobility spectrometry (IMS). Please refer to our envESI section for more information on our IMS nitrate/nitrite system development. We are also interested in exploring FAIMS (field asymmetric IMS) as a possible separation technique for our envESI system.

Another technology that we are evaluating for the nitrate/nitrite measurements is UVRR (ultraviolet resonance Raman) spectroscopy. Laboratory experiments showed extremely high selectivity for both the nitrate and nitrite as well as low detection limits close to .1 ppm (as N). Together with our industrial collaborators, we are developing a smaller and less expensive UVRR systems platform that could be installed at a wastewater treatment plant. In 2005, dTEC Systems was granted a U.S. patent on the application of UVRR to wastewater treatment plant process control systems. You can find more information on application of UVRR to nitrate/nitrite measurements in this article.

UVRR spectra for range of nitrite concentrations

Optical sensors for suspended solids concentration measurements that are used in wastewater treatment industry have a number of limitations. The most important include sensor errors due to fouling, non-reliable operation at higher solids concentrations, and the need for color compensation. Acoustic sensors do not have these problems, but they cannot be used at lower concentrations therefore their application is typically limited to sludge level and density measurements. We are interested in developing new dissolved/suspended solids sensors that overcome some of the typical limitation of both the optical and acoustic technologies.

We are interested in developing a low-cost distributed fringing electric field (FEF) sensor system capable of making simultaneous measurements in a large number of small packages of baked food products. The primary use for such a system will be to accelerate food aging studies performed by large food companies. The FEF sensors will be used to continuously monitor a range of physical phenomena in the bulk of the packaged food products. Some examples of the different processes that could be monitored with this system include moisture migration, loss of texture and stability in homogeneous and multi-layered products, and layer-to-layer sipping and diffusion. The FEF measurements are non-destructive and inherently safe. Therefore, the food samples can be later analyzed by other techniques and tasted. In the future such system could be used at the food manufacturing lines for total quality control. Also, unlike most of the other method, the electric field penetrates the bulk of the sample allowing accurate parameter estimation for both the outer and the inner layers of the product.

The technology enabling these new sensors is high precision dielectrometry. Shielded hybrid electric field sensor will measure complex dielectric permittivity of wastewater providing an accurate estimate of the total solids concentration. Concurrently, the sensor will separately monitor the properties of the volume adjacent to electrodes surface. This additional measurement will allow the system to auto calibrate for the sensor head fouling.

Preliminary lab-bench solids concentration sensor tests

With proper calibration, the operational limits of the new electric field sensors should be very wide, covering most of the solids concentration ranges typically encountered in wastewater treatment. The possible application of this technology would include settling tank monitoring, sludge level and density measurements, novel centrifuge control systems, and others. Currently, we are conducting proof-of-concept laboratory experiments and developing a fully functional sensor prototype. We are trying to establish sensor’s practical operation range and accuracy, and study the effect of operating conditions on the sensor performance.

Changes in moisture concentration and its spatial distribution within food samples are critical data pieces for the food engineer developing a new food product. Current methods for monitoring moisture concentration in foods both during the production and shelf life are based primarily on destructive techniques such as titration, vacuum oven evaporation, other gravimetric methods, and, naturally, visual examination. Several non-destructive techniques are being developed as well, most known ones being ultrasonic and nuclear magnetic resonance (NMR) imaging. The ultrasonic methods are useful when a good contact with the sample is possible and the detection/imaging is focused on discontinuities. The NMR methods require complex and bulky equipment, often providing excellent imaging capabilities, but remaining unpractical for in-situ continuous monitoring of food samples, especially when massive parallelization is expected.

Hybrid FEF sensor measurement system

We are interested in developing a low-cost distributed fringing electric field (FEF) sensor system capable of making simultaneous measurements in a large number of small packages of baked food products. The primary use for such a system will be to accelerate food aging studies performed by large food companies. The FEF sensors will be used to continuously monitor a range of physical phenomena in the bulk of the packaged food products. Some examples of the different processes that could be monitored with this system include moisture migration, loss of texture and stability in homogeneous and multi-layered products, and layer-to-layer sipping and diffusion. The FEF measurements are non-destructive and inherently safe. Therefore, the food samples can be later analyzed by other techniques and tasted. In the future such system could be used at the food manufacturing lines for total quality control. Also, unlike most of the other method, the electric field penetrates the bulk of the sample allowing accurate parameter estimation for both the outer and the inner layers of the product.

We are interested in developing a low-cost distributed fringing electric field (FEF) sensor system capable of making simultaneous measurements in a large number of small packages of baked food products. The primary use for such a system will be to accelerate food aging studies performed by large food companies. The FEF sensors will be used to continuously monitor a range of physical phenomena in the bulk of the packaged food products. Some examples of the different processes that could be monitored with this system include moisture migration, loss of texture and stability in homogeneous and multi-layered products, and layer-to-layer sipping and diffusion. The FEF measurements are non-destructive and inherently safe. Therefore, the food samples can be later analyzed by other techniques and tasted. In the future such system could be used at the food manufacturing lines for total quality control. Also, unlike most of the other method, the electric field penetrates the bulk of the sample allowing accurate parameter estimation for both the outer and the inner layers of the product.

First prototypes of FEF food sensor electronics

At this time, we are looking for financing to allow us to conduct a series of evaluation experiments. These experiments will be a continuation to the preliminary feasibility studies and sensor development efforts that were conducted by our team members and our academic collaborators. The specific issues that we will address in these experiments are system noise immunity, sensor accuracy, and repeatability. We will also concentrate on developing the algorithms and calibration datasets that would help educe the information about the different product properties from complex dielectric spectra obtained with the multi-mode electric field sensor heads.