Electrobiotic sensors have been proposed for detecting toxic substances in a variety of environments. Electrobiotic sensors would be inexpensive, compact units that would be easy to use and could be deployed either singly or in large numbers, depending on the size of an environment to be monitored and/or the need to locate a toxic source within a larger area. For example, multiple electrobiotic sensors might be deployed on a battlefield or at a large-scale mining operation, whereas a single electrobiotic sensor might be used to monitor the air in a laboratory or at an assembly bench where toxic chemicals are used.

An Electrobiotic Toxic-Agent Sensor would contain and monitor a population of small nematodes. Electronic circuitry would detect motion or lack of motion of the nematodes. Upon detecting cessation of the motion (presumably a result of environmental toxicity), the circuitry would transmit a signal. The total volume of the sensor would be about 1 in.3 (16 cm3).
The term "electrobiotic" was chosen for these sensors because the front line of sensitivity would be biological entities and the responses of these entities to toxic substances would be sensed and processed by electronic circuitry. More specifically, a typical electrobiotic sensor (see figure) would include very small live nematodes in a suitable medium deposited on an active-pixel sensor (APS) [a state-of-the art single-chip integrated-circuit array of photodetectors and active readout circuitry]. The movements of the nematodes, which are mutatable to be agent-specific, would be detected through differencing between prompt and delayed pixel readout signals.

A control application-specific integrated circuit (ASIC) on a single chip would monitor the pixel-differencing output of the APS chip to detect movement. If movement were detected, no further action would be taken. If movement were not detected, the control ASIC would activate a microfluidic injection of nicotine to stimulate activity of the nematodes. If activity were still not detected, the nematodes would be assumed to be dead, implicating a toxic environment. The ASIC would then activate the radio transmission of a simple binary signal containing encrypted data on the location of the sensor as determined by a Global Positioning System (GPS) receiver that would also be part of the sensor. If multiple electrobiotic sensors were dispersed over a large area, then they could communicate with each other to relay their status and location data to a central receiver/repeater unit, which would be placed in the area during dispersal of the sensors.

The radio transmitter in an electrobiotic sensor could be very simple and short-lived and its range could be limited [e.g., of the order of a mile ( ≈ 1.6 km)]. Therefore, the power demand of the sensor could be satisfied with a very small battery like that used in a hearing aid.

The life cycles of nematodes are typically of the order of 4 days. However, nematodes can be sustained in a dormant state for a few weeks to a few months. Furthermore, they can be frozen for very long periods. Hence, electrobiotic sensors could be stored at low temperatures for future use.

This work was done by Philip Moynihan, Robert Stirbl, and Roger Kern of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP)free on-line at www.nasatech.com/tsp  under the Electronics & Computers category. NPO-20721

Topics:
Biosensors Detectors Electronic equipment Electronics & Computers Global positioning systems (GPS) Integrated circuits Navigation and guidance systems Sensors Sensors and actuators
This Brief includes a Technical Support Package (TSP).
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Electrobiotic Toxic-Agent Sensors

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NASA Tech Briefs Magazine

This article first appeared in the May, 2000 issue of NASA Tech Briefs Magazine (Vol. 24 No. 5).

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Overview

The document discusses the development of electrobiotic toxic-agent sensors, which integrate biological entities, specifically nematodes, with microelectronics to create a highly sensitive and cost-effective detection system for toxic agents. This innovative approach addresses the need for reliable sensors that can be rapidly deployed in areas suspected of contamination.

The core of the sensor system consists of a population of live nematodes placed on an Active Pixel Sensor (APS) array. The movements of these nematodes are monitored through pixel differencing. An Application-Specific Integrated Circuit (ASIC) control chip oversees this monitoring process. If the nematodes exhibit movement, no action is taken; however, if movement is not detected, the system activates a microfluidic injection of nicotine to stimulate the nematodes. Should there still be no activity, the nematodes are presumed dead, indicating a toxic environment. The ASIC then transmits a binary signal, including GPS location data, to identify the sensor's specific location.

The document highlights the compact design of the sensor, which includes all necessary electronics for movement detection, such as timing, control, and signal processing, integrated into a CMOS-compatible chip. The power requirements are minimal, allowing the use of a small battery similar to those found in hearing aids. The nematodes have a life cycle of about four days but can be kept dormant for extended periods, making it feasible to stockpile these sensors for future use.

Deployment methods for the sensors range from manual placement to remote dispersal via low-base artillery rounds, allowing for flexible operational strategies. When deployed in suites, the sensors can communicate with each other, forming a relay system to transmit their status to a central receiver.

The document emphasizes the novelty of this technology, which combines the biological sensitivity of nematodes with the rapid response capabilities of microelectronics. This method offers a direct means of detecting toxic agents through the cessation of nematode movement, distinguishing it from traditional detection methods that rely on algorithms and indirect measurements.

Overall, the electrobiotic toxic-agent sensor represents a significant advancement in environmental monitoring technology, providing a reliable and efficient solution for detecting hazardous substances in various settings.