Year: 2005
Type: article
Abstract: Center for Embedded Networked Sensing CENS Sensor Research: Overview Thomas Harmon, Chih-Ming Ho, Jack W. Judy, Yu-Chong Tai, Ira Goldberg, Tatyana Bendikov, Dohyun Kim, Arnaud Benahmed, Qing He Introduction: New sensor technologies to improve the capabilities of wireless sensor networks A miniature Small, low-cost, robust, reliable, and sensitive sensors are needed to enable the realization of practical and economical sensor networks. Although there are a large number measurands that are of interest for sensor-network applications (e.g., seismic, temperature, light, sound, magnetic, chemical, etc.), appropriate commercial sensors exist for many of these measurands. However, one prominent exception is the fact that appropriate chemical sensors are not available. It is for this reason that the sensor technology effort within CENS is researching the design, fabrication, and implementation of chemical sensors that have the specifications needed for sensor networks. The first targeted application is nitrate detection in ground water. Group Organization: Multiple different approaches to develop chemical sensors for CENS CE NS In order to detect nitrate in aqueous solutions with concentrations in the range of 1 to 100 µM, the sensor technology development team is taking multiple approaches. Two efforts are focused on developing miniaturized and selective electrochemical sensors and one effort is focused on developing a microscale liquid chromatography (LC) system. The development of the electrochemical sensors are both near-term projects but will be highly tailored for nitrate detection. The development of the LC system is a long-term project but has the potential to be a general sensing system. The projects and teams are described below. Why Nitrate (NO 3- ) Sensor Important? Nitrate is a major contaminant in ground water Nitrate-sensor applications – In-situ nitrate monitoring, environmental science/biology research, and precision farming Sensor requirements Inexpensive, small, remotely operable, detection range (1 μM to 1 mM) Proposed Solution: Leverage CENS technologies to develop a wireless neural interface interfac e Surface Plasmon Resonance (SPR) Arnaud Benahmed and Chih-Ming Ho (UCLA) Surface Plasmon (SP) based sensors can detect a wide range of molecules with slight variations, making them attractive for an adaptive sensor network Within CENS, nitrate and algae detection are two examples of applications of SP sensing under development HPLC Chip-Based Chemical Sensing Qing He, Yunan Miao*, Terry Lee*, and Yu- Chong Tai (Caltech/City- of- Hope) Miao *, Yu - (Caltech/City - of - Signal Voltage (mV) We invented a new sensor, the Surface Plasmon Band Gap Sensor (SPBG) that can be miniaturizable and detect a wide range of molecules Surface plasmons (SP) are electromagnetic waves propagating on the surface of a metallic interface Their wavelength is strongly dependant of molecular binding on the surface We showed that it is possible to use nanostructures to measure SP wavelengths using the plasmonic band gap phenomenon: when molecular binding occurs, the propagation of surface plasmon through the nanostructures is forbidden High Performance Liquid Chromatography (HPLC) is one of the most powerful, versatile, and widely used separation techniques It allows separation, identification, purification, and/or quantification of the chemical compounds in complex mixtures By miniaturizing HPLC system onto a chip, significantly lower sample and solvent requirements, higher mass sensitivity, and lower cost can be achieved Moreover, portable HPLC chips can be used for field tests and/or networked sensing, which is impossible or impractical for conventional desktop A Signal HPLC systems Ion Chromatography Separation of Multi-Anion Mixture On-Chip Packed Column. L 8mm/W 100 µ m/H 25 µ m. Hamilton PRP-X110 Anion Exchange 7 µ m Resin SO 4 Cl F NO 2 Br NO 3 PO 4 1. Fluoride: 12.5ppm 2. Chloride: 25ppm 3. Nitrite: 25ppm 4. Bromide: 25ppm 5. Nitrate: 25ppm 6. Phosphate: 25ppm 7. Sulfate: 25ppm C B Time Sample Chromatography Column Separated Components Time (sec) Conditions: 1.7mM NaHCO3, 1.8mM Na2CO3. Isocratic. Conductivity. Micromachined Amperometric Nitrate Sensor Dohyun Kim, Ira Goldberg, and Jack W. Judy (UCLA) Electrochemical Method (Amperometry and Potentiometry) are: Electrochemical reduction of nitrate: NO 3 + H 2 O + 2 e − → NO 2 + 2 OH − NaOH supporting electrolyte, working electrode (Ag), reference electrode (Ag/AgCl), counter electrode (Pt) A’ Outlets Ground water contains Quick-turn Inlets Luer-lock couplings cm many ionic/non-ionic Top Plate A Sample Reservoir interfering species Anion Selective Selective Permeable Diffusion Membrane Anion-Permeable measurement Microfabricated Membrane and Sensor Chip Rubber Sheet achieved with an Electrolyte Rubber Reservoir Plate Calibration Curve: anion-selective Reference Working Electrode Electrode membrane Sensing 1.4e-6 1.2e-6 1.0e-6 8.0e-7 6.0e-7 4.0e-7 2.0e-7 Chip 1 (r =0.997) Chip 2 (r 2 =0.993) Linear Regression Potentiometric Electrochemical Detection Tatyana Bendikov and Thomas C. Harmon (UC Merced) We are working on a novel concept, that of scaleable nitrate sensors created in a form appropriate for dense soil deployments- -mimicking root fibers Our sensors will be inexpensive and environmentally benign and minimally disturb the soil moisture propagation and chemical transport regime during observations Potentiometric Response for NO Ion Proof-of-concept with nitrate-doped polypyrrole ion selective electrodes (Bendikov et al. 2005 Sensors and Actuators B: Chemical) simple in design and operation, easily minaturized, low power, sensitive Electrochemical deposition (constant current conditions) of polypyrrole dopped with nitrate onto carbon fibers substrate Voltage (mV) Carbon fibers, 7 µ m diameter each, ~ 20-30 fibers, 1.2 cm depth 3 days after deposition (Slope: 54.3 mV, R = 0.9999) 9 days after deposition (Slope: 54.4 mV, R = 0.9999) Chip Microfluidic Channel Counter Electrode 19 days after deposition (Slope: 52.6 mV, R = 0.9999) 5-6 ppm Bottom Plate Charge(C) -log(NO 3 ) Concentration (µm) UCLA – UCR – Caltech – USC – CSU – JPL – UC Merced
Language: English
Subfield: Computer Networks and Communications
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W329540776