Clean Technology : Environmental monitoring


Detecting Seismic S Waves with Unprecedented Accuracy

UW–Madison researchers have developed an automatic and extremely accurate method for detecting features of interest in seismic data, including S waves and P waves. Unlike currently available (and error-prone) phase detection methods, the new software identifies potential picks in a single pass through the data without needing to estimate parameters or build a model. Seismic features are identified based on their similarity to a reference set of examples.

The software utilizes a k-nearest neighbors approach. This approach is based on a nonparametric time series classification method.

Robust Biological and Chemical Detection Method and Microfluidic Device with Liquid Crystal Sensing Element

UW-Madison researchers have now developed an improved method for autonomously generating stabilized liquid crystal thin films and two microfluidic devices that employ the technique for detecting trace amounts of biological agents and chemical compounds.  The handheld microfluidic devices each contain a microchannel defined by grooved polymer materials sandwiched between glass substrates.  Priming the device involves filling the microchannel with liquid crystal material, which fills specific nickel-plated structures in the channel, and flushing the liquid crystals outside the container with the laminar flow of an aqueous solution.  This method allows for automatic formation and rapid regeneration of the stable aqueous/liquid crystal interface. 

In the presence of a target compound the orientation of the liquid crystals changes, altering optical properties of the liquid crystals through a phenomenon known as optical birefringence.  After the analyte has been introduced into the channel, a white light is passed through a first polarizing lens, the microfluidic device, and a second orthogonally oriented polarized lens.  The intensity of the light, determined by the degree of optical birefringence, is detected by a microscope to confirm the presence or absence of the specific target in the aqueous solution.

The microfluidic biological and chemical detection device with a liquid crystal sensing element allows for automatic formation of the sensing interface through its design and operation.  The device design also provides better control of the interaction between the aqueous target containing solution and liquid crystal region.  By providing a robust device and method, as well as reducing the need for advanced technical training, the improved detection apparatus will greatly enhance in-field applicability of biological and chemical sensor technologies.

Detecting and Determining the Concentration of a Target Bioagent

UW-Madison researchers have now developed an improved sensor that requires only one membrane to determine target concentration. The membrane is fabricated from a polymeric material that dissolves when exposed to a particular biological agent. To detect the agent, the membrane is contacted with a sample of fluid. If the target bioagent is present in the fluid, the membrane dissolves at a speed dependent on the concentration of the agent. A beam of light with a specific wavelength is passed through the membrane to determine the degree of dissolution, and a detector generates an output voltage in response to the intensity of light transmitted. The change in voltage can be monitored to determine the concentration of the target agent.

Device and Methods for Liquid Crystal-Based Bioagent Detection

UW-Madison researchers have developed a sensitive, selective and efficient liquid crystal-based device and method for detecting bioagents and other biological molecules. The device uses membranes that are comprised of a polymerized antigen or substrate of an enzyme, such as botulinum toxin (BoNT). A liquid crystal is in contact with one surface of the membrane. To detect a bioagent, the other membrane surface is contacted with an aqueous solution suspected of containing the antibody or enzyme. If the bioagent is present in the solution, the membrane containing the substrate degrades, leading to a detectable change in the orientation of the liquid crystal.

Method and System for Retrieving Information from Wireless Sensor Nodes

UW-Madison researchers have developed an alternative approach to retrieving information from a wireless sensor network. In this method, a computationally powerful Wireless Information Retriever (WIR) interrogates a group of computationally “dumb” wireless sensor nodes with wideband radio-frequency signals. The sensors act as “active scatterers” and generate a multipath response to the interrogation signal that includes the sensed data. The WIR then separates the signals from different sensors by matched filtering to their location-dependent response to rapidly retrieve their information.

Bioagent Detection Device

UW-Madison researchers have developed an inexpensive, real-time wireless microsensor for detecting biological agents in water supply networks and other aqueous environments such as the milk supply. This system includes a microdevice composed of a sampling chamber and a capacitor chamber connected by a channel. A biosensitive membrane blocks the channel between the two chambers.

To detect a biological agent, a sample of fluid is introduced into the sampling chamber and contacts the membrane. If a target bioagent is present in the fluid, it causes the membrane to become permeable or even to dissolve. When this occurs, fluid flows from the sampling chamber into the capacitor chamber, creating a very large change in impedance and an extremely large electrical output signal. The output signal is then wirelessly transmitted to a device that alerts the user to the presence of the target bioagent.

Use of Liquid Crystals and Affinity Microcontact Printing to Detect Chemicals and Biomolecules

UW-Madison researchers have developed methods for using affinity microcontact printing and liquid crystals to simply and easily detect a ligand or receptor. Affinity microcontact printing captures a specific ligand from a sample and “stamps” the ligand onto a detection surface so that the ligand’s presence can be visualized with liquid crystals.

First, an “affinity stamp” is created by covalently linking a capture protein, which binds the target ligand, to a polydimethylsiloxane (PDMS) base. The stamp is then placed into contact with a sample, and if the target ligand is present in the sample, the stamp will bind it. Next, the stamp is contacted with a detection substrate to transfer the target ligand, if present, from the stamp to the substrate. Liquid crystals are added to the top of the detection substrate, and a functionalized glass slide is placed on top of them. The ligand is present in the sample if the liquid crystal display appears disordered or disrupted.

Horizontally-Configured Surface Plasmon Resonance (SPR) System

UW-Madison researchers have developed an improved SPR imaging device. Designed to be more compact and easily adjusted, the improved SPR instrument allows horizontal mounting of the sample, as well as horizontal placement of the light source and camera on either side of the instrument. In addition, the optical assembly incorporates four simple, planar mirrors for easy manual control of the angle of incidence of light.

A Portable Instrument for Surface Plasmon Resonance (SPR) Imaging

UW-Madison researchers have now constructed a smaller, portable SPR instrument for sample analysis in field situations. To reduce the size, complexity and power consumption of the instrument for field use, the researchers made several design improvements. In particular, they devised a way to replace the high-power light source of the bench top model with a standard, low-power light-emitting diode (LED), and created a simplified, automated sample handling system to minimize the need for operator training.

Spectroscopic Detection of Water Contaminants Using Glow Discharges from Liquid Microelectrodes

UW-Madison researchers have developed a micro-fabricated, on-chip spectroscopic system for on-site, real-time analysis of trace contaminants in liquids and gases. The system works as follows: Two microfluidic channels transport sampled water from two large reservoirs into two smaller pools, or liquid electrodes. A micro-glow discharge generated between the liquid electrodes sputters water molecules and impurity atoms into the discharge region. The resulting discharge emits discrete wavelengths of light that correspond to specific atomic transitions. By analyzing a spectrum of these wavelengths, the chemical composition of the water can be determined.

System for Calculating the Spatial-Temporal Effects of Environmental Conditions on Animals

UW-Madison researchers have developed an accurate method to predict and thereby diminish or even prevent these negative effects. Their system uses an integrated set of models to incorporate all the conditions needed to accurately predict how animals (both ectotherms and endotherms) will react to changes in their surroundings.

The software package contains three subsections: a microclimate model, a model for warm-blooded animals with fur or feathers, and a model for cold-blooded animals, including insects and reptiles. Input for the models is taken from the animal’s temperature-dependent behaviors, morphology and physiology.

The software has been successfully used in a number of cases. For example, Professor Porter used it to calculate annual respiratory volumes for several sizes and species of birds in Florida. As a result of this work, the EPA elected to cancel registration of a particular pesticide in Florida.

Detecting Compounds with Liquid Crystals

UW-Madison researchers have developed a novel method and device for detecting the presence of gas phase chemical compounds such as environmental contaminants with liquid crystals. The device consists of a thin film of liquid crystals overlaying a nanostructured surface that hosts receptors for binding a chemical compound of interest. When the target compound is present in a sample, it diffuses through the film of liquid crystals and binds to the receptors on the surface. Binding of the compound causes the liquid crystals to change their orientation, a shift that is readily observed with the naked eye.

Micromachined Shock Sensor

UW–Madison researchers have developed a micromachined shock sensor that has an array of acceleration sensing units formed to make contact at different levels of acceleration. This allows the shock sensor to measure a wide range of accelerations from 10g to 150g. The system also contains a built-in redundancy that circumvents challenges with the closing and opening of electrical contacts.

Sensitive Bioassay for Detecting Dioxins and PCBs

UW-Madison researchers have developed a highly sensitive biological assay for detecting serious environmental pollutants such as dioxins and polychlorinated biphenyls (PCBs), as well as other molecules that bind to the aryl hydrocarbon receptor. The assay utilizes a transgenic yeast cell line that expresses AHR, ARNT and either ARA9, ARA3 or Src (or a combination). These toxin-responsive elements are linked to a reporter gene, so that a detectable product is expressed in the presence of planar aromatic hydrocarbon molecules.