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Sensors for detection
- 1. Team leader: David Moore Spandana Misha Eugenia Gagik Caitlin SENSORS FOR DETECTION
- 2. Overall Concept What is a Nano-Sensor? ○ Any biological, chemical, or surgical sensor point to detect information about nano-particles on the microscopic level Why use nanotechnology for sensing? ○Large surface area ○Miniaturizes devices ○Reduce power consumption ○Increase Sensitivity ○Direct detection Chemical Vs Mechanical Chemical- Detect change in conductance when a semiconducting carbon nanotube comes into contact with certain chemicals Mechanical ●AFM cantilever ○One atom will make it bend
- 3. Overview of Applications Nano-sensors improve the quality of life Major applications include: -Medical field -national security -aerospace -integrated circuits Bomb Detection Bombs becoming more and more advanced & better hidden ●Nanotechnology increases sensitivity ■nano-sensor can sense parts per billion Bio-Sensors Cure disease and save lives ●Medical uses at the cellular level Issues: Improve imaging performance Bomb Detection Issue: Expense ●Wide variety of materials for explosives ●Vast number of avenues explosives can be deployed ●Lack of inexpensive sensors with high sensitivity and selectivity
- 4. What has been discovered & engineered in the past? Mechanical Sensing ●First mechanical sensors - balances ●Electromechanical sensors - molecules absorbed onto surface of sensor and change electrical properties ●Surface Acoustic Wave (SAW) sensors - molecules absorbed onto a crystal causing unique surface vibrations Current Flaws: ●Sensors are either too lack sensitivity or require delivery to lab for analysis Smaller (molecular-level) sensors will allow for more efficient testing on the field and give real-time results.
- 5. Existing Sensors Chemical Sensors ●Indicators change color in the presence of a chemical. Ex. Phenolphtalein --> ●Testing for antigens in bloodstream specific to disease ●Acoustic wave immunosensors - sensors change resonant frequency when proteins associated with disease attach to their surface Flaws: ●Antigen sensing takes time and can return false results more commonly than is acceptable ●Acoustic wave immunosensors provide real-time results but require a high volume of sample/protein for accuracy ●Large sensors cannot enter the body Molecular-level sensitivity is necessary for accuracy when a low volume of sample is available and needs less sample in general
- 6. Biosensors: Some Applications Detection devices using biological elements (cell receptors, antibodies, etc.) Ex. canary in the mine ●Nanoscale: ○pregnancy tests ○cancer cell detection ○glucose monitoring ○pesticide detection ○food analysis ○pollution/ air and water filtration ○DNA specific medication ●Ex. of Application: Commercial glucose monitor uses glucose oxidase enzyme ●Biosensors not necessarily always expensive technology ●Not seen in more applications due to: ○lack of need for level of precision
- 7. Biosensors ●Like a chemical sensor-- able to detect biological molecules or viruses ●Due to nanoscale, can detect trace pathogens, protein enzymes, pesticides, etc. ●Nanotubes- electron transfer with oxioreductase enzymes ●Surface Plasmon Resonance- probe quantifies equilibrium between proteins, DNA, ligands The 3 Main Parts ●sensitive biological element (interacts w/ partical being analyzed) ●transducer (transforms signal from interaction into something measurable) ●biosensor reader device (reads signal and displays results) The 3 Basic Types: ●photometric ●electrochemical ●ion channel switch
- 8. Biosensors: Impact on Society ●main interest- technology used to sense various medical conditions in people ●leap forward for diagnostic medicine ●future for personalized medicine: protein analysis ●better precision in [insert types] of detection, higher sensitivity
- 9. The electronic nose technique can overcome the challenges of the bomb‐sniffing dogs. COMPOSITION: 1.Chemical sensing system (using mechanical nano-devices like cantilevers) 2.Sampling system 3.Pattern‐recognition system The sensing system- Array of sensors: different electrical responses OUTPUT: The sensor array generates fingerprints. Artificial neural networks recognize different fingerprints. Bomb detection Nanosensors
- 10. Mechanics of Nano bomb sensing ●Nanomechanical effects due to molecular adsorption are used for trace explosive detection. ●Cantilevers- Modes of operation: 1)Surface stress reaction: Explosive molecules bind to the cantilever, induce a surface stress-the cantilever bends. 2)Differential adsorption-immobilising a layer on one side of the cantilever. Surface stress reaction Differential adsorption Sniffing out bombs: http://www.sciencedaily.com/videos/2008/0704-sniffing_out_bombs.htm
- 11. Nano Bomb Detectors: Societal Impact ADVANTAGES: ●Portability ●Precise ●More sensitive ●More reliable ●Does not require bulky and expensive equipment ●Do not need to be fed or trained ●Low cost ●Can prevent major industrial and mining accidents Direct Economic Impact- Formation of new companies that can exploit these technologies
- 12. POTENTIAL IMPACTS Advantages of this technology: * Increased sensitivity, accuracy and precise information gathering * Can be used in a wide variety of fields like robotics and IC's. * Low power, miniature and rapid response Challenges/Limitations of nanosensors: * High cost of production (around $0.6 to $2.7 billion)
- 13. UNDER DEVELOPMENT Environmental: Proven to detect air pollutants Responsible for reducing air pollution as well as water pollution. Hydrogen Sensors: Use a layer of closely spaced palladium nanoparticles. When hydrogen is absorbed the palladium nanoparticles swell Causes shorts between nanoparticles which lowers the resistance of the palladium layer. Chemical: ● Zinc oxides nano-wire and Carbon nanotube detection elements: Capable of detecting a range of chemical vapors. ● Gold nanoparticles on a polymer film: Detect volatile organic compounds (VOCs).Polymer swells in presence of VOCs, changing the spacing between the gold nanoparticles and the resistance of the gold layer. ● Nanoporous silicon detection elements: Could be incorporated into cell phones. Allows a very widespread network of sensors to detect chemical gas leaks or release of a toxin. ● Nanocantilevers: Chemical sensor using nanocantilevers that are oscillating at their resonance frequency. When the chemical attaches to the cantilever it stops the oscillation, which triggers a detection signal. Biological: Detect biological molecules such as viruses. Cantilever is coated with antibodies that capture the particular virus When a virus particle attaches to the antibody the resonance frequency of the cantilever changes. Mechanical: Sensors powered by electricity generated by piezoelectric zinc oxide nanowires. Allows small, self contained, sensors powered by mechanical energy such as tides or wind.
- 15. Exam Questions Gagik - What is one flaw associated with electromechanical sensors and mass spectrometers?
Editor's Notes
- AT LEAST 3 DAYS BEFORE NEXT MEETING, SEND DAVID AN EMAILED UPDATED VERSION OF PPT
- -Size of Structure decreases, surface to volume ratio increases considerably -reduction of size of sensing part- miniaturizes devices -increase sensitivity (HOW) *sensitivity of conventional biosensors in range 10^3-10^4 colony forming units (CFU/ml) while nano is ~1 -limits of detection can be lower, very small quantities of samples can be analyzed -Many applications demand miniaturisation to reduce power consumption for integration into portable devices. Some of the major applications are the medical field, national security, aerospace, integrated circuits, and many more. Medicinal uses of nanosensors mainly revolve around the potential of nanosensors to accurately identify particular cells or places in the body in need. Chemical nanosensors are also constrcucted by using carbon nanotubes to detect the different properties of many gaseous molecules.Ionization of gases and atomospheric concentartion level of hydrogen and oxygen at the manufacturing plants and chemical research labs are managed with the help of chemical nanosensors.Chemical sensors can also detect the speed,wavelength and level of molecules in the strong light. mention whole genre, then narrow in on exactly what we'll be discussing (i.e. chemical sensors) Mechanical- AFM cantilever (no chem. involved) Chemical- coated with a chemical that will react with analyte Add: Coatings limit what can reach the sensor element- prevent electrical interference from charged particles Many applications demand miniaturisation to reduce power consumption for integration into portable devices. a sensor that utilizes/detects phenomena exhibited in the nano-scale regime Because of the small size of nanotubes, nanowires, or nanoparticles, a few gas molecules are sufficient to change the electrical properties of the sensing elements. This allows the detection of a very low concentration of chemical vapors. Some of the major applications are the medical field, national security, aerospace, integrated circuits, and many more. There are a number of challenges currently with the production of these nanosensors, however, when they become perfected for regular use they will have a number of advantages over the sensors that are used in today’s technology. These sensors are ultra sensitive and can detect single virus particles or even ultra-low concentrations of a substance that could be potentially harmful. One of the most largely funded areas of research in nanosensors is biosensors.
- Dogs- part per million while nanosensor part per billion improve imaging performance by enabling faster (video rate) coverage of larger surfaces No commercial systems are currently available with the same criteria of specificity, sensitivity, speed, ease of use and low cost. expensive endeavor because of a number of factors, such as the wide variety of materials that can be used as explosives, the lack of easily detectable signatures, the vast number of avenues by which these weapons can be deployed, and the lack of inexpensive sensors with high sensitivity and selectivity. Problems with nanosensors reduction of the cost of materials and devices and improving the reliability of them packaging of them and putting them into a product that is useful for consumers. Mass production is difficult because the methods that are used to create the nanosensors are typically incompatible with those used in the making of the electronics that amplify and process the signals that the sensors generate. Also mass production is difficult for the simple reason that most nanosensors are still physically assembled by hand since finding a way to efficiently manufacture them in mass production is still being researched. We need to improve imaging performance by enabling faster (video rate) coverage of larger surfaces, eventually down to the molecular scale. We also need to perfect nanopatterning methods to improve resolution, overlay and throughput capabilities The ISSUE is a little too specific for background information Important questions to answer: What's the problem? Make the audience think, "wow, that really is a problem! How do we cure more diseases/ find more bombs?" Then answer... "How do nanosensors solve the problem?" later in the ppt. Most bombs contain NO2, nano-sensors can trace levels of vapors from these explosives Issue: Not always easy to detect a bomb because any molecule can bond to the carbon nanotube and contribute or remove an electron Solution: coat nanotube with material responsive only to certain chemicals
- Edit currentflaws- too big? DONE Gagik, Please add notes here about what the speaker should say for each bullet point. Then, check for small grammar errors. Thanks! One of the earliest biosensors- canary in the mine We can think of the first ever mechanical sensors used being scales, which depended on lever arms determining when two weights are equal. Electrochemical sensors depend on molecules being absorbed into their surfaces in order to change their electrical properties. They test for changes in conductivity, voltage, or amperage. Surface acoustic wave sensors absorb a molecule onto a piezocrystal. This causes surface waves to vibrate the surface of the sensor, which can then be detected. The flaws with these sensors are that they are either too big and bulky to be brought directly into the field, or require the specimens transported back to the lab for further analysis. The ones that are not too bulky are usually not sensitive enough for high-profile application. Sensitivity at the molecular level would allow for the sensors to be small enough to brought onto the field and boost their efficiency at the same time.
- all slides leading up to the two examples can be general cancer detection- too specific nanosensors "can't stuff larger stuff into the body" Be careful about the FLAWS: Is that problem really a product of size? DONE Gagik, Please, once again, add in the extra information the speakers should be saying. Then, you can cut down the wording on this slide and make it more concise. Thanks Early chemical sensors include colored indicators, which provide visual feedback in the presence of a certain chemical. This includes phenolphtalein for acidity and Lugol's solution for starches. Antigen testing uses antibodies to detect antigens specific to disease in the body. This usually involves processing in a lab from a few hours to a few days. Acoustic wave immunosensors work similar to SAWs in that they absorb proteins into their surface. This changes the resonant frequency of the sensor, allowing for detection of the presence of the protein. These methods either take too long to process or require a very large sample in order to test accurately. Molecular level sensitivity will allow for testing with a small sample and provide real-time results. Furthermore, it will provide smaller sensors which plausibly can be introduced into the body.
- change order make this an intro to biosensors Description of useful/ unique device(s) or technique(s) why don't we use them for more things? why details...
- work it backwards coatings-- should show up in concepts and background if it's going to come up in the examples Fundamental scientific principle(s) or general operating principle(s)/functionality: (HOW BIOSENSORS WORK Caitlin FIND ANOTHER ADVANTAGE BESIDES SENSITIVITY FOR BIOSENSORS SIZE OF SENSORS CHANGING- SMALLER SENSORS, BETTER IMAGING First, how they work Then, some advantages Describe 3 types Nanostructures such as carbon and organic nanotubes (NT), nanowires and nanotubes have a very high surface area to volume ratio and unique electrical and optical properties that can be exploited for highly sensitive molecular adsorption detection. For instance, electrical conductivity in a nanotube changes drastically due to interacting with molecules of an explosive analyte, as a result of highly selective adsorption. The great promise of nanotubes as biosensing elements is the potential to develop systems where direct electron transfer between enzymes and electrodes is possible. This innovation is key to the development of mediatorless (third-generation) enzyme biosensors, where no co-substrate is required in the recycling of the enzyme back to its active form. The mediatorless enzyme biosensor using nanotubes is most obviously applicable to the oxidoreductase enzymes where redox reactions cause electron flow and the extremely high conductivity of the nanotubes is used to detect this flow. powerful and quantitative probe of the interactions of a variety of biopolymers with various ligands, biopolymers, and membranes, including protein:ligand, protein:protein, protein:DNA and protein: membrane binding. It provides a means not only for identifying these interactions and quantifying their equilibrium constants, kinetic constants and underlying energetics, but also for employing them in very sensitive, label-free biochemical assays
- Contribution of new science or innovation narrow down to one of 3 types... explain how nanotechnology works as a [photometric] sensor scratch privacy invasion don't get into ethics Cut- Privacy invasion: - biosensors can predict the future profile of a person = insurance companies could potentially deny coverage http://cyclotron.aps.org/weblectures/biology-physics/lieber/real/sld025.htm find more information on disease marker proteins and serum proteins misc. info- DNA field-effect sensor (specific type)
- nanowires and nanotubes have a very high surface area to volume ratio and unique electrical and optical properties that can be exploited for highly sensitive molecular detection. For instance, electrical conductivity in a nanotube changes drastically due to interacting with molecules of an explosive analyze. electronic nose device is composed of a chemical sensing system, sampling system and a pattern‐recognition system, such as an artificial neural network . The sensing system consists of an array of sensors, with each sensor in the array giving a different electrical response for a particular target vapour introduced into the sensing chamber. The combined output from the sensor array forms a finger‐ print, or signature, that is unique for a particular odour. Pattern recognition techniques based on artificial neural networks were developed for learning different chemical signatures. Nanomechanical effects induced by molecular adsorption offer unprecedented opportunities for trace explosive detection.
- Nanomechanical effects induced by molecular adsorption offer unprecedented opportunities for trace explosive detection. Nanomechanical-sensors such as cantilever beams have many modes of operation. For example, when explosive molecules bind to the detection molecules on the cantilever made in nano‐structured silicon , this will induce a surface stress and the cantilever will bend. Differential adsorption is obtained by immobilising a selective layer on one side of the cantilever. Nanocantilevers are expected to provide ultra‐high‐sensitivity mass detection, ultimately approaching the single‐molecule level
- nano sensors not for ordinary use.... not always right counterexample: pregnancy tests Be careful... high cost of production, non-compatible and non-reliable? not always... sometimes cheaper, sometimes better for everyday use
- For your info the picture with the hydrogen sensor is an online article!! I put it there as a picture not plagiarizing anything I understand what you were trying to do, but unfortunately, when we are presenting the ppt, it will still look like a text box containing words that are not our own. It's not really a picture.
- Societal Impacts: Go to Science Caberet- podcasts- The ethics of Nanotechnology DONE!
- *Save your refs as you research in the references ppt