آزمایشگاه سیگما

دانشگاه تهران

آزمایشگاه سیگما

آزمایشگاه سیگما

مقدمه‌ای بر حسگر‌های گازی

انسان همواره در پی کشف حقایق و قوانین حاکم بر طبیعت زندگی خود بوده است. و از گذشته تا کنون با استفاده از روش‌های ساده و پیچیده، راه‌های مختلفی را به منظور شناسایی عوامل محیطی به کار گرفته است. امروزه نیاز به حسگر‌های دقیق در کاربرد‌های محیط زیستی، کشاورزی، صنعتی، تشخیص‌های پزشکی و ... احساس می شود. در واقع، حسگر‌ها، تبدیل کننده‌های انرژی به یک نوع انرژی معین هستند که منجر به تولید یک سیگنال خروجی قابل فهم و قابل پردازش ایجاد می شود. حسگر‌های گاز، دسته‌ی مهمی از حسگر‌ها هستند که قادرند نوع و غلظت یک گاز معین را در محیط شناسایی کنند.

 

در طراحی این حسگر‌ها، گازی که غلظت آن مدّ نظر است را گاز هدف (target)می‌نامند. این گاز با تغییر در خواص فیزیکی و یا شیمیایی افزاره شناسایی می‌گردد. و برمبنای میزان تغیرات ایجاد شده توسط گاز هدف، نسبت به زمان عدم حضور آن غلظت محاسبه می‌شود. تاکنون روش‌های مختلفی در حسگری گاز‌ها به کار گرفته شده است. تغییر رسانایی نیمه‌هادی‌های جاذب گاز، تغییرات اپتیکی و تغییرات دمایی از این دسته اند. جدول1 خلاصه‌ای از روش‌های موجود را نشان می دهد.

در چند دهه‌ی اخیر، نیمه‌هادی به دلیل جذب مناسب، حساسیت بالا، قابلیت کوچک‌سازی و قیمیت پایین مورد توجه قرار گرفته‌اند. با استفاده از موادی چون اکسید روی، اکسید مس و اکسید قلع، حسگر‌هایی با حساسیت یک قسمت در میلیارد (1 ppb)  حاصل شده است. به کار بردن نانوساختار‌ها همانند نانو‌لوله‌های کربنی، نانو‌ذرات و نانو‌سیم‌های فلزی همگی روش‌هایی برای افزایش حساسیت حسگر‌های نیمه‌هادی محسوب می شود.

امروزه با وجود پیشرفت‌های گسترده و حتی ارائه نمونه‌های تجاری، طراحی و ساخت حسگر‌ها با چالش‌هایی چون طول عمر، تکرار پذیری، قدرت تشخیص کم و قابلیت مجتمع سازی مواجه است. به کارگیری فن‌آوری میکرو و نانو روش مؤثری در بهبود عملکرد حسگر‌ها است. انتظار می رود با استفاده از این تکنیک‌ها روز به روز شاهد پیشرفت این افزاره‌ها بود.

جدول 1- انواع حسگر‌های گازی مورد استفاده و خواص قابل تغییر

نوع حسگر تغییرات خواص
نیمه‌هادی رسانایی الکتریکی
اثر میدانی(خازن‌ها، دیود‌ها، ترانزیستور‌ها) تابع کار(قطبش الکتریکی)
پیزوالکتریک جرم
اپتیکی پارامتر‌های اپتیکی(بازتاب، عبور، جذب، ضریب شکست، طول نوری)
کاتالیزوری گرما یا دما
الکتروشیمیایی نیروی محرکه‌ی الکتریکی یا جریان الکتریکی در سلول‌های شیمیایی حالت جامد
خواندن 764088 دفعه آخرین ویرایش در شنبه, 10 بهمن 1394 ساعت 14:32

1417198 نظرها

  • پیوند نظر Wilber جمعه, 03 آذر 1396 ساعت 05:53 ارسال شده توسط Wilber

    The United States http://slowoseniora.pl/bioglan-coq10-50-mg-capsules-200-9c5 bioglan coq10 50 mg capsules 200 The video was filmed Sept. 3, and the version posted on YouTube has been viewed more than 1.9 million times. It begins with Cordles face blurred as he describes how he has struggled with depression and was simply trying to have a good time with friends going from bar to bar the night of the accident. He then describes how he ended up driving into oncoming traffic on Interstate 670. Cordles face becomes clear as he reveals his name and confesses to killing Canzani.
    http://www.ilsa.be/Form/index.php/provestra-price-in-india-8ff#exposed provestra manufacturer That was the case on Sunday when the offensive line in front of him turned into a sieve, providing barely a speed bump for the onrushing Carolina Panther defenders. Against a defense that had just three sacks in the first two games, Manning was sacked seven times — six in the first half — and four times on the first 10 plays of the Giants’ embarrassing 38-0 loss.
    http://staffscc.net/wppalmer/index.php/fluconazole-mg-dosage.pdf fluconazole 150mg tablets over the counter It's not the first time Calderoli has been under fire for racist remarks: In 2006, he was forced to resign as a minister in Silvio Berlusconi's government after he wore a T-shirt on state-run television featuring one of the Prophet Muhammad cartoons that had inflamed the Muslim world.
    http://unicoba.com.br/climaxol-le-prix.pdf climaxol gouttes lehning “A 20 percent risk reduction translated across the entire United States is a fairly substantial number,” said Dr. Bruce Giantonio, an associate professor of medicine at the Abramson Cancer Center of the University of Pennsylvania.
    http://www.dailymarkets.info/prostate-healthy-foods-for-reducing-spasms-a25#active prostate health young living essential Under the theme “Advancing Productivity through Innovation, Modernization and Expansion,” the GuyExpo 2013 trade and investment exposition will be held at Guyana’s Sophia Exhibition Site from Oct. 3 to 6, according to Chevon Singh of the Guyana Tourism Authority.

  • پیوند نظر Lonnie جمعه, 03 آذر 1396 ساعت 05:53 ارسال شده توسط Lonnie

    What do you do? http://www.amazingcakeideas.com/proextender-johor-bahru-1d1 how to use proextender "We have no reason for haste, but slowly and surely we must get our machinery rolling and get our troops ready for battle," Orban said in a speech on Budapest's Heroes' Square, where he first made his name by calling for a pullout of Soviet troops in 1989. "Be prepared: we can now finish what we started in 1956."
    http://www.westernworldsaddlery.com/blog/allopurinol-worsen-acute-gout-6dac.pdf allopurinol gout medicine side effects The Dow Jones industrial average was up 237.81points, or 1.61 percent, at 15,040.79. The Standard & Poor's 500Index was up 27.92 points, or 1.69 percent, at 1,684.32.The Nasdaq Composite Index was up 73.46 points, or 2.00percent, at 3,751.24.
    https://www.greendiscoverylaos.com/much-does-xenical-cost-canada.pdf much does xenical cost canada In Iraq, a similar deal fell apart after US officials were unable to reach an agreement with the Iraqis on the same issue that would have allowed a small training and counterterrorism force to remain there. The United States completely pulled out of Iraq after the deal collapsed.
    http://skrabac.com/cheap-online-buy-yohimbe.pdf#chart yohimbe xtra whiteline The superseding indictment in U.S. District Court in Manhattan said Mathew Martoma succeeded in getting at least two doctors to provide illegal information in a scheme that stretched from 2006 to 2008 while he worked at SAC Capital Advisors. The Boca Raton, Fla., man has pleaded not guilty to conspiracy and securities fraud and is scheduled to appear in court Friday. He is free on bail.
    http://www.for-darmstadt.de/pristiq-medicine-dosage-1dd pristiq takes time to work Carl Tobias, a professor of constitutional law at the University of Richmond, said the governors decision was astute because nullifying marriages now taking place would be difficult and expensive. Its a pragmatic decision, he said.

  • پیوند نظر Sebastian جمعه, 03 آذر 1396 ساعت 05:53 ارسال شده توسط Sebastian

    Do you know each other? http://www.laptopskins.org.uk/what-do-valium-taste-like.html valium and drug tests In May, Judge Gillen, who has asked for the media not uncover the personality of the youngster included for the situation, requested the mother to agree to the circumcision, while additionally cautioning her not to advise her child she was against the methodology.

  • پیوند نظر Jerrell جمعه, 03 آذر 1396 ساعت 05:53 ارسال شده توسط Jerrell

    Some First Class stamps http://www.dunamis.us/amaryllis-belladonna-care.pdf amaryllis lily bulbs for sale in india Both Amgen and Sanofi/Regeneron do not expect definitivedata on cardiovascular outcomes for their drugs until largertrials conclude in 2017

  • پیوند نظر Johnnie جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Johnnie

    We work together http://www.westernworldsaddlery.com/blog/what-is-the-work-of-manforce-tablet-6dac.pdf manforce condom latest ad With the show's producers deciding to take the program's news report in a different direction, Wood moved on to public relations, training corporate executives how to present themselves to the media and working for the American Legion and other organizations.
    https://www.superluigibros.com/amoxicillin-dosage-for-sinus-infection-in-pregnancy-5ada.pdf amoxicillin tablets formulation As would fall in line with Gov. Cuomo’s commitment to hold spending growth to a maximum of 2% a year. He has imposed that discipline on state government, and he has capped property-tax increases outside the city to that amount without a special vote.
    http://slowoseniora.pl/folic-acid-dose-methotrexate-rheumatoid-arthritis-e61 how long does it take for methotrexate to work for psoriatic arthritis
    The launch marks a milestone for Obama's signature domestic policy achievement, which aims to provide subsidized healthcare to millions of the uninsured, the most ambitious U.S. social program since Medicare was introduced in the 1960s.
    https://www.superluigibros.com/keflex-500mg-tid-5ada.pdf keflex 500mg tid It is to be highly regretted that the defenseless people who protested in Morocco over the release of the rapist, last week, were brutally beaten by Moroccan Riot Police as demonstrated by photos that were published around the world.
    http://www.kayserimeydan.com.tr/permethrin-treatment-lice-6e0 permethrin treatment for pubic lice Capriles fired back with one of his typical denunciations of the president's inner circle - and a rallying cry for opposition lawmakers not to be seduced by the efforts to secure the extra vote Maduro needs.

  • پیوند نظر Nevaeh جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Nevaeh

    Directory enquiries https://www.andmetics.com/risperidone-1mg-picture-15e#disguised risperidone medscape It's a form of condescension that believes we can't think for ourselves or decide what is relevant to us on our own. It makes you wonder if there's something going on at the Fukushima nuclear power plant you don't know about (there is). And it makes you afraid to click on anything lest you be judged. One more hit on a self-destructive, scantily clad reality TV star, and you're branded an air-head for life.
    https://www.snapsite.us/orlistat-p-receptor-397f.pdf fingras orlistat 120 mg precio China has faced criticism from Western countries for whatthey call its cultural and religious repression of ethnicminorities, including Tibetans and Muslim Uighurs in the vastwestern Xinjiang region.
    https://www.andmetics.com/celebrex-200-mg-costco-15e#futile celebrex or ibuprofen for back pain "Until he actually gets in the batting cage and swings freely and then gets in there for batting practice, he won't play,'' Melvin said. "I'd doubt tomorrow. We want to make sure he gets in swings on the field.''
    http://www.benchevents.com/viagra-kupovina-beograd.pdf viagra resepti tallinna Shares of Citigroup advanced 2.3 percent to $52.00after the third-largest U.S. bank by assets reported a 26percent increase in adjusted quarterly profit. The S&P 500financial industry sector index was up 0.4 percent.
    http://slowoseniora.pl/folic-acid-dose-methotrexate-rheumatoid-arthritis-e61 25 mg methotrexate dosage So, if it was the tangible chemistry between Johnson and Hunnam that locked the actors in to do the movie, does Hunnams departure mean Johnsons character will be recast as well?

  • پیوند نظر Kenneth جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Kenneth

    I'm sorry, he's https://www.basicsofsikhi.com/what-to-say-to-your-doctor-to-get-viagra.pdf#borrowed how many viagra can you take in a week So far, he's mostly watched in silence as those wounded in the attack described how he shouted "Allahu Akbar!" — Arabic for "God is great" — and drew a weapon and opened fire on unarmed soldiers. Hasan is representing himself, but has raised few objections and asked only two witnesses questions.
    http://skrabac.com/proxeed-opinie.pdf proxeed plus london "It was a struggle, a bit of a roller coaster. But for the whole team it was fantastic. I think the whole team is proud of what they achieved," he said as he was mobbed by well-wishers and television crews.
    http://sapa.fi/metoprolol-succinat-ct-95-mg-56d#geological cost of metoprolol succ er 50 mg Southwest winds around 5 knots then becoming west around 5 knots in the afternoon. Bay and inland waters smooth. Scattered thunderstorms. Tuesday night will bring north winds around 5 knots. Bay and inland waters smooth. Isolated thunderstorms.
    http://www.honkatrading.com/ginsengplus-cena-08c#seedling original korean ginseng creme cena The agreement states that a Security Council resolutionshould allow for regular assessments of Syria's behaviour and"in the event of non-compliance ... the UN Security Councilshould impose measures under Chapter VII of the UN Charter".
    https://www.andmetics.com/promethazine-codeine-syrup-online-buy-211 phenergan syrup paediatric dose 'Waiting for the Dr... Courtney & I are ready to go! Is it a boy or a girl??? #BabyLopez' Mario Lopez and wife Courtney get ready for the birth of their second child on Sept. 10, 2013. Lopez later revealed that the baby was a little boy named Dominic.

  • پیوند نظر Adam جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Adam

    I'd like to apply for this job http://slowoseniora.pl/folic-acid-dose-methotrexate-rheumatoid-arthritis-e61#worn methotrexate rash on face The night took a turn for the worse when a customer overheard LiLo get into a “disturbance” with a staffer, as she begged to keep the bar open past closing and was acting “insanely belligerent.”
    http://tehranmusicdl.ir/cheap-cialis-20mg-pills.pdf#symbol buy online cialis canada "The company may be faced with quality control issues (maybebecause of the surge in demand) that may attract FDA's attentionor require retooling the manufacturing process," they wrote in anote to clients.
    http://skinnedcartree.com/super-kamagra-kopen.pdf#properly en ucuz kamagra damla The policing strategy seems very ineffective. The water cannon doesnt seem to even be on a high pressure. On days as hot as this it just cools them down. No word of any follow up arrests on ring leaders from the previous nights either. It must be terrible to be a PSNI officer on the front line up there. Expected to put up with such severe violence knowing the perpetrator will likely get off scot free.
    http://www.gravityforce.co.uk/shatavari-kalpabaidyanath.pdf shatavari ingredients From the beginning of the Syrian civil war, he said, "it was clear there were three possible endgames. One, outside intervention — which will not necessarily end the conflict in Syria; two, an internal agreement among the Syrian factions; three, a decisive victory by of one side."
    http://themalthouseironbridge.co.uk/propranolol-fara-reteta-1c2#statesman propranolol creme kaufen Kroger said the deal should add 6 to 9 cents to its earnings per share in the first full year after it closes, excluding transition and transaction expenses. [ID:nPnCL44152] It has financing plans ready, including a bridge loan commitment. [ID:nWEN009FV]

  • پیوند نظر Arnold جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Arnold

    A book of First Class stamps https://www.basicsofsikhi.com/what-to-say-to-your-doctor-to-get-viagra.pdf is it against the law to buy viagra online
    Tavenner, a former nurse who is widely respected as a policy expert without partisan allegiances, replied that Obamacare's approaching implementation has come as good news for businesses that want to provide health coverage for their workers.
    http://snowbility.co.uk/buy-viagra-uk-nhs.pdf discount female viagra pills Prime Minister Morgan Tsvangirai makes his third attempt to end Mugabes long grip on power. Tsvangirai tried to delay the election without success. He says Mugabe is using dirty tricks, such as keeping dead people on the electoral roll, to perpetuate his hold on power.
    http://www.honkatrading.com/buy-generic-accutane-no-prescription-8de accutane cost canada “You’d like to see us protect the football and be more conscious about it, but he’s going to try to make a throw that he thinks is there,” Ryan said. “In that case, with hindsight being 20-20, I’d like to see him throw the ball away there and not force it.”
    http://www.thompsonslighting.co.uk/when-will-generic-viagra-be-available-in-the-us-f853.pdf#largely where is the cheapest place to buy viagra online
    "As a good corporate citizen, we are committed to addressing the concerns raised by the government and authorities in the market in which we do business and will comply with the fine stipulated by the NDRC," FrieslandCampina said in an emailed statement.
    http://www.honkatrading.com/motrin-generic-2f7#pea pediatric tylenol motrin dosing chart But Thomas does not do anything slowly, and that applies to suffering injuries, as well. Just seconds into the game's first play, Thomas turned his right ankle and was immediately leveled by California's Bryce McGovern.

  • پیوند نظر Alex جمعه, 03 آذر 1396 ساعت 05:52 ارسال شده توسط Alex

    What do you want to do when you've finished? https://www.allcenter.com.br/isotretinoin-after-alcohol-132 retin a and tretinoin cream Army Colonel Denise Lind, who is presiding over the trial, last week rejected a request by the defense to throw out the aiding-the-enemy charge, saying that Manning's military training made it clear to him that any information released on the Internet could get into the hands of enemy agents.
    http://skrabac.com/butea-superba-gel-india.pdf#mortgage butea superba liver damage Hammerson says it has reached “significant milestones” in all three with planning registered for the Croydon regeneration project and consultations held with shoppers about what awaits them at Brent Cross.
    http://southasianlife.com/discreet-viagra-online-uk-c12b.pdf where to buy real viagra uk
    “They are high school boys, just like any other high school,” says Henderson International School headmaster Seth Ahlborn. “They live together; they eat together; they play together,” he said. “They just spend a lot of time together just like high school kids. It’s just smaller.”
    http://skrabac.com/cialis-20mg-12-preisvergleich.pdf#cranny acheter du cialis sur internet "It's not just myself or someone at five under. Someone back at three and two can still have a run at this thing. I think I'm confident enough in my own ball-striking to not be intimidated by Henrik's good ball-striking."
    http://rollstud.com/getting-generic-viagra-in-canada.pdf#swamp buy female viagra in india Cold case detectives have long pored over the strange case of the Boston Strangler, and their big break came thanks to increased success in extracting DNA profiles from very old, very small, and very degraded evidence samples.

نظر دادن

از پر شدن تمامی موارد الزامی ستاره‌دار (*) اطمینان حاصل کنید. کد HTML مجاز نیست.

درباره ما

 گروه پژوهشهای کاربردی MEMS دانشگاه تهران در مهر ماه 1394 با هدف انجام پژوهشهای کاربردی به منظور دستیابی به فنآوری های Hitech در حوزه های MEMS&NEMS که مورد نیاز صنایع مختلف کشور باشد، با تلاش جمعی از اساتید و دانشجویان رشته مهندسی سیستم های میکرو و نانو الکترومکانیکی دانشگاه تهران تاسیس گردید. 

بالا
ما از کوکی ها برای بهبود وب سایت استفاده می کنیم.ادامه استفاده شما از کوکی ها در سایت رضایت شما را از کوکی ها نشان می دهد. مشاهده جزئیات