Givare och system 1 Givare Elektrisk Mekanisk Kemisk Biologisk Magnetisk Impedans Sensor Spänning Ström Frekvens 2 1 Inför labben Givarlab Ingen labbhandledning 4 olika mätsituationer Jobbar 4 och 4 En uppgift vid varje station! 3 Mätproblem Vad skall vi mäta? Hur skall vi mäta? Med vilken givare? Datablad Lära känna givaren!!!! 4 2 Instruktioner för projektpresentationer. Presentationernas längd, 15 minuter. Ni kan använda PowerPoint (eller liknande) En annan utsedd grupp opponerar ca 5 minuter Innehåll: Ett mätsystem där ni fördjupar er på en eller flera delar. ! 5 Bedömningskriterier • Att presentationen riktar sig till rätt målgrupp, BME-studenter i årskurs 3 • Disposition av presentationen • Tydlighet • Samarbete mellan presentatörerna • Hur hjälpmedel används • Det tekniska innehållet i presentationen 6 ! 3 Alkoholsensor 7 Alkoholsensor Olika typer Sensorerna kan vara baserade på: • Metalloxid • Bränslecell 8 4 Alkoholsensor Metalloxid SnO2, mikromekaniskt tillverkad Billig Liten Enkel Robust Enkel avläsning, resistans 9 Alkoholsensor Metalloxid 10 5 Alkoholsensor Metalloxid Nackdelar: • Ospecifika • Ej stabila under lång tid 11 Alkoholsensor Bränslecell • Dyr • Bättre än metalloxid • Ger en spänning ut • Ospecifik • Polisens vapen mot rattfyllerister 12 6 Alkoholsensor Bränslecell 13 Mekaniska givare • Tryckgivare • Flödesgivare • Accelerometer 14 7 Givarprinciper 15 Tryckgivare 16 8 Tryckgivare Historik Rörelse överförs till en visare 17 Vilket tryck Absolut tryck Gaugetryck Diferentiellt tryck 18 9 Vilket tryck Absolut tryck Tryck mätt mot vakuum Gaugetryck Tryck mätt mot atm Diferentiellt tryck Tryck mätt mot annat tryck 19 Tryck - enheter 20 10 Er tryckgivare 21 Er tryckgivare 22 11 µ-mekanisk tryckgivare 23 Flödesgivare 24 12 Flödesmätning • Volymflöde, m3/s, µl/min • Massflöde, kg/s 25 Venturirör 26 13 Bernouillis lag Summan av lägesenergi och rörelseenergi konstant. 1 p + "v 2 + "gh = konstant 2 ! v= q A ! 27 Venturirör 28 14 Bernouillis lag Summan av lägesenergi och rörelseenergi konstant. 1 p + "v 2 + "gh = konstant 2 q= Cd " A2 $A ' 1# & 2 ) % A1 ( ! 2 " v= q A 2" ( p1 # p2 ) ! * 29 ! Obstruktionsmätare 30 15 Corioliskraft Massflöde 31 Corioliskraft Massflöde 32 16 Varmtrådsanemometer 33 Gasflödesgivare Honeywell 34 17 Flödesmätare 35 Accelerometer 36 18 Accelerometer 37 Accelerometer 38 19 Micro accelerometer 39 Micro accelerometer 40 20 Accelerometer 41 Accelerometer 42 21 Accelerometer 43 Mikrosensorer Kemiska & Biologiska sensorer 44 22 Flow sensor 45 Accelerometer 46 23 Kapacitiv accelerometer 47 Kapacitiv accelerometer 48 24 Mikrosensorer Varför mikro/nano 49 Varför mikro/nano • Små • Snabba • Kiselsensorer med elektronik • Ingen matrialutmattning i kisel • Ingen eller liten hysteres • Polymerteknik (kemiska system) • Laminärt flöde 50 25 Varför mikro/nano Kemi • Små prov volymer = låg analytkonsumtion • Korta diffusionslängder • Mikroteknologi = reproducerbara system • Batch tillverkning = billiga komponenter • Avancerade sensorer/Multisensor chips • High Sample Throughput (HST) 51 Kiselsensorer för termiska signaler • Termoelektriska effekter • Termoresistorer • Dioder och transistorer • Temp. sensorer för bla. flöde, tryck & IR, 26 Termoelement ΔV = (αa-αb)ΔT Seebeckeffekten i metaller 1. Ferminivåns temperaturberoende 2. Diffusionskoefficienten för laddningsbärare 3. Termodiffusion 27 Termospänning mätt mot platina Termostapel på kisel 28 Termoresistans Platina Termoresistans i halvledare (extrinsiskt kisel) Resistiviteten vs. temp Elektrontäthetets vs. temp 29 Fotodiod Elektron-/hålpar som bildas i utarmningregionen för den backspännda pn-övergången ger upphov till fotoströmmen. Karakteristik för pnfotodioden Open circuit Short circuit Voc = kT/e ln(IL/IS+1) 30 Olika typer av fotodioder Optiska Givare 62 31 Optiska Givare 63 Kemiska Givare • Resistiva • Kapacitiva • Mekaniska • Kalorimetriska • Metall-oxid gassensorer • Fälteffekttransistorer (ISFET, CHEMFET) • Elektrokemiska (potentiometriska, amperometriska) • Akustiska vågsensorer 64 32 Användnings områden • • • • • • Medicinsk diagnostik Implanterbara biosensorer Monitorering i tillverknings/process industrin Miljö analys/övervakning Farmaceutisk screening Forskning 65 Elektrokemiska Det finns även en mängd andra elektrokemiska mätmetoder t.ex. olika former av voltametri. 66 33 Kapacitiva Kan användas till att mäta; specifika gaser, pH eller humiditet 67 Fälteffekttransistorer 68 34 Charles Lieber • Single particle detection • Ultrasensitive detection of proteins for cancer • Chemical and biological warfare agents • Large-scale addressable arrays for screening in biology and medicine 69 Charles Lieber 70 35 Charles Lieber 71 Charles Lieber 72 36 Charles Lieber 73 Charles Lieber 74 37 Sensorer för massa 75 Sensorer för massa Sara G Nilsson et al 76 38 Sensorer för massa S Ghatnekar-Nilsson et al Table 1. The table shows the results from the mass loading experiment, where f 0 is the resonant frequencies before the deposition of the Au layer, and ! f is the frequency change after the Au deposition. The thickness of the Au layer, !tAu , is calculated using equation (4). L f0 !f ! f / f0 !m/m 0 !tAu Figure 3. Frequency spectra from the as-fabricated array of two cantilevers obtained before and after deposition of Au. The added mass generates frequency shifts of 9.7 and 5.7 kHz for the 81 and 106 µm long cantilevers, respectively. Sara G Nilsson et al thin layer of Au was thermally evaporated on the back surface of the cantilevers. As can be seen in figure 3 the added mass generated different frequency shifts for the individual cantilevers. The shorter cantilever has an original frequency of 680 kHz. After the Au deposition the frequency was reduced by 9.7 kHz. For the longer cantilever, with an original frequency of 406 kHz, the frequency was reduced by 5.7 kHz. Normalizing the frequency shifts to the original frequencies, ! f / f0 , yields the same value of 0.014 ± 0.0003 for the two cantilevers, i.e. an accuracy of 0.1%. Assuming a uniform metal coverage and ρAu = 19.3 g cm−3 , we obtain values for the thicknesses of the evaporated metal layers (using equation (4)) to be 12.6 and 12.5 nm for the two cantilevers, respectively, see table 1. Although we have by no means optimized the mass response of this system, the experiment serves as a proof for the MFSAC method displaying that the same relative change in mass (!m/m ) added onto the cantilevers will generate different frequency shifts depending on the original resonant frequencies. A major advantage with this system is that the frequency response from all cantilevers is collected at the same time, i.e. within the time frame of one measurement. The signal is thus monitored having the same environment and conditions for the entire array. By functionalizing each cantilever it is possible to obtain a true label-free detection since each frequency shift depends on the individual cantilever length. Hence, even if the masses of the molecules interacting with the differently functionalized cantilevers are similar, which is not very unlikely, we will obtain discrete frequency shifts. Assuming 100% affinity, we thus obtain a fully label-free detection system. This is in contrast to earlier measurements employing arrays of cantilevers of equal lengths not being able to discriminate binding of similar masses, even though a 100% affinity is assumed. Although we have only tested this novel concept with arrays of two and three cantilevers, there is no reason to believe that there are any limitations in the number of cantilevers in the array (other than pure practical considerations such as the laser spot size). Furthermore, the 81 µm 680 kHz 9.7 kHz 0.0143 0.0285 12.6 nm 106 µm 406 kHz 5.7 kHz 0.0140 0.0281 12.5 nm MFSAC method can easily be extended to use other detection schemes, e.g. capacitive read-out [11]. The experiments in this work have been carried out in ambient air conditions, serving as a proof for the MFSAC method. However, pursuing the method into sensor applications in the biological area requires that the measurements be performed in a liquid environment. Previous work has investigated the dynamic behaviour of Si cantilevers in liquid, and the corresponding frequency shift as phospholipid vesicles were adsorbed onto the cantilever surface [8]. The next step will be to combine the MFSAC method with a liquid environment. The approach of using a FIB system to machine arrays of cantilevers was used as a means for rapid prototyping. 77 [12] (NIL) and electron beam Both nanoimprint lithography lithography [9] are viable lithography alternatives, where the cantilever dimensions easily can reach the nanometre scale. NIL also meets possible industrial needs. The next approach would be to fabricate arrays of nanocantilevers, thereby increasing the mass sensitivity both for each individual cantilever and, using the MFSAC detection method, for the array in total. This would generate another dimension to the sensitivity of the system as a mass sensor providing true labelfree detection with an unprecedented resolution and detection capability. 4. Conclusion In this work, a novel concept of using different lengths in an array of cantilevers has been investigated. The method has been denoted MFSAC: multi-frequency signal analysis from an array of cantilevers. The array of micromechanical oscillators generated a spectrum of different resonant frequencies, where each frequency correlated to the corresponding individual cantilever. Although the mass response of the system was by no means optimized, a thin layer of Au on the as-fabricated array of two cantilevers generated the same ! f / f0 for the two cantilevers, within 0.1% accuracy. A major advantage with this system is that the frequency response from all cantilevers is collected within the same time frame, offering the possibility for true label-free detection. This simultaneous detection of several frequencies in one spectrum has great benefits in mass sensor applications since the same environment and conditions prevail for the entire array during the measurements. Enzymatiska sensorer Glucose sensor GOD Glucose + O 2 " Gluconic acid + H 2O 2 GOD=Glucose oxidase 5236 Acknowledgments The authors acknowledge experimental assistance from Petra Reinke and Jermaine Coleman at the Department of Materials ! 78 39 Mikroenzymreaktor 1. anisotropt etsade vertikala flödeskanaler 2. Kanalväggarna är etsade poröst 79 Enzymatiska sensorer Glucose sensor GOD Glucose + O 2 " Gluconic acid + H 2O 2 GOD=Glucose oxidase ! 80 40 Glucose sensor Glucose sensor 81 Glucose sensor Mäter blodsockerhalten i blodet med hjälp av spektroskopi 82 41
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