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8440 Central Avenue, Newark, CA 94560(877) 794 4296;  www.kwjengineering.com

www.transducertech.com; www.ecosensors.comwww.detectcarbonmonoxide.com

KWJ ENGINEERING Inc. is a high-tech rapidly growing business with the mission to revolutionize the capability for detection and situational-awareness for the purpose of improving health, safety, and security for mankind and the environment.

“Safety, Security, Surveillance Sensors for the 21st Century”

CPAC Summer Institute,  July 2010

Electrochemical Detection of Ozone in Air and Waterwith CNT-Electrocatalysts: Industrial Applications for MEMSAnd Other Sensors.

J.R. Stetter1*, M. Findlay, Jr.1, V. Patel1, and D. Ebeling2

1KWJ Engineering Inc., 8440 Central Avenue, Newark, CA 94560, USA2Wisconsin Lutheran College, Milwaukee, WI USA*Corresponding author: Email jrstetter@kwjengineering.com or jrstetter@gmail.com

Nanotechnology, Sensors, MEMS, Multidimensional Arrays, Intelligence, and Applications.

Joseph R. StetterPresident/CTO, KWJ Eng. Inc.;  Newark, CAProfessor and Co‐Dir: Int. Center for Sensor Science and Engineering, IIT, Chicago, ILProfessor [honorary], Oakland University, Rochester, MI

Presented atCPAC,  Summer Institute, July, 2010University of Washington, Seattle, WA

The opinions expressed are  those of the author and not those of the affiliations! 

Outline• Nanotechnology • CNTs – single walled carbon nanotubes [SWCNT]• Ozone – uses, toxicity, measurement science• Electro‐catalysis and sensing• Results and discussion

– Comparison AGS and HMOx; smart Sensors.

• Process air and water analysis: R‐Cl, O3, HC.• MEMS sensor progress• Concluding Remarks

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Nanotechnology insights• Apparently Magical things happen at the nanometer scale:

– SWCNT=all atoms are surface atoms,  • quantum effects – small particle and wave distinction blurs [domain of DeBroglie and 

Heisenberg]• materials get their properties here; materials [intrinsic, extrinsic, molecular, optical, …]• significant information and context is created at the nano‐level • Physics – chemistry – biology meet at the nano‐scale!• New fields emerge here!  Molecular‐electronics, bio‐electronics;• Different forces dominate at nano‐dimesions [surface forces, …] 

• We have known this, but never been the focus of our investigation.• Nano‐science and technology will revolutionize our lives:

– Medical, environmental, electronic, optical, mechanical, analytical [sensors & instruments] 

– Challenges:• Nano is interdisciplinary in a world of academics ordered by discipline.• Nano takes resources• Nano often requires unique designs• Nano often requires new processing [materials, tools, and protocols]

Nanoscience Nanofiction

© Vic Olliver

Nanorobots repairingred blood cells

Colloidal Nanocrystal Shapeand Size Control: The Case of

CobaltVictor F. Puntes,1* Kannan M. Krishnan,2 A. Paul Alivisatos 1*

We show that a relatively simple approach for controlling the colloidal synthesisof anisotropic cadmium selenide semiconductor nanorods can be extended tothe size-controlled preparation of magnetic cobalt nanorods as well as spher-ically shaped nanocrystals. This approach helps deÞne a minimum feature setneeded to separately control the sizes and shapes of nanocrystals. The resultingcobalt nanocrystals produce interesting two- and three-dimensional super-structures, including ribbons of nanorods.

REP O R TS

www.sciencemag.org SCIENCE VOL291 16 MARCH2001 2115

Nanotechnology

© QuantumDot Corp.

Fluorescentlylabeled cells

Nanoscience

though most inventions

begin as fictions …

NanofictionNanotechnology

Sensors/devices are a material product of science and technology!

• Assertions about the importance of Sensors:– Sensors are the material counterpart to language centered knowledge

– Devices are on a par with theory– Ability to impart/carry/transmit knowledge

– Great Instruments/Sensors can have the same impact as the great theoretical contributions

BEYOND IDEAS  devices/SENSORS/instruments

Top Technical challenges• National Academy of Engineering 2008

Make solar energy affordable Provide energy from fusion Develop carbon sequestration Manage the nitrogen cycle Provide access to clean waterReverse engineer the brain Prevent nuclear terror Secure cyberspace Enhance virtual reality Improve urban infrastructure Advance health informatics Engineer better medicines Advance personalized learning Explore natural frontiers 

CAN ANYONE ENVISION SUCCESS IN THESE CHALLENGESWITHOUT BETTER SENSORS?

9

Chemical Sensor Applications/High Volume Markets• Sensing Needs:

– Automotive (odor detection with air conditioning and ventilation systems)– Environmental/indoor air quality (vent gases, Cryptosporiduium in water/HVAC)– Oil & gas (fence‐line monitoring, personal monitoring VOCs)– Chemical (differential analysis of gas mix.)– Pulp & paper (monitoring bleaching process and toxics)– Semiconductor Processing (facilities awareness and toxic gases)– Home/Office (CO monitoring  with long‐life/low co$t)– Clinical diagnostics (insulin, drug detection, disposalble O2)– Food & beverage industries (spoiling, flavor and odor detection; processing)– Pharmaceutical (enhance drug discovery)– Telecommunications (hydrogen in switching centers)– Bioprocessing (CO2 Malcohol)– Cellphones – CO and other ubiquitous threats.– Methane in homes, mines, transmision, distribution, gathering, wells) 

• Need for a Complete System Solution – Smart Sensors– Sample handling, support subsystems (power, processing, comm.)– Miniature and low power architecture– Integrated Orthogonal Sensors/Array for awareness

Analytical Chemical Sensor needs• What do we ask a sensor to do?

– Simple signal, compensated concentration, …?– Complex information, complex endpoint:

• Is it toxic? Where is it from? Is it the same as?

• GEDANKEN EXPERIMENT – “the perfect analysis”– Every molecule is indentified in space/time

• 1 cc of air at STP ~ 3 x 1019 molecules!• One Human  Breath [~ 500 cc or 1022 molecules!]

06/11/09 CONFIDENTIAL AND PROPRIETARY ‐MAY NOT BE REPRODUCED OR DISTRIBUTED

Sensors must be more capable 

What do sensors do?Where do they fit?

Sensors vs Instruments: trade‐space evaluation of cost and utility;SENSORS MUST REPLACE INSTRUMENTS

[compare: selectivity, sensitivity, response time, stability, cost]

Better Sensitivity / Selectivity / Accuracy/Validity

Cos

t of O

wne

rshi

p

Spectra-Photometers & Chemiluminescence

Non-dispersive infrared spectroscopy

Gas Chromatography & GC/MS

IRMS

Fourier Transform Infrared Spectroscopy

SENSORS are the bottom line

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About 2500 different chemical compounds have been reported to date and there are perhaps billions of compounds present in every 

single breath!

Joseph R. Stetter, Chapter 1, “Experimental Methods in Chemical Sensor and Sensor Array Evaluation and Development,” in“Computational Methods for Sensor Materials Selection, M.A. Ryan, A.V. Shevade, C.J. Taylor, M.L.Homer, M. Blanco, and J. R. Stetter, editors, 2009, pp3-46. )

Ozone Measurement Techniques• UV absorption spectrometers [.1ppb‐100ppm]• Electrochemical reduction [50 ppb‐100ppm]

– Amperometric Gas Sensor– O3  + 2 H+ + 2 e‐ = H2O + O2

• Catalytic ‐ chemiresistor  [0.1ppb‐2ppm]– HMOx sensors

• Colorimetry [one order of magnitude]– Indigo blue method

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Uses of Ozone• Needs for Ozone sensors:

– GOOD OZONE /BAD OZONE• Processes for Cleaning, Disinfection, and Purifying.

• Safety alarms and health protection – 100 ppb• Environmental monitoring  ‐ 180 ppb

• Applications for sensors– Casino air, Cruise Ship – 50 ppb– Restaurant food & wine barrel cleaning– Laundry – prison, hospital, nursing home.– Aquariums– Drinking water– Fracture water, Gulf‐coast contaminated water

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CNT MATERIALSELECTROCATALYSTS ‐ ELECTRODES

• Hybridization>sp2 but <sp3 –– More stable than graphite but less than diamond– Conductive and semi‐conductive– Stable in acid and base and at anodic potentials– Can be fabricated into porous gas electrodes

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Graphitic Carbon to Nanotube

• carbon nanotubes

• rolled graphene sheet•Grown on catalyst•LPCVD process•20 torr, 900C•harvested•purified

Graphitic carbon

Carbon Nanotube Electronic Structure

1D nanotube2D materials

Carbon Nanotube Electronic Structure

Counter electrode

Reference electrode

Working electrode

Porousmembrane

Catalyst/ working electrode

ElectrolyteO3

O2

e-

H+

WE: O3 + 2 H+ + 2 e- = O2 + H2O

CE: H2O = ½ O2 + 2H+ + 2 e--=

Ozone Amperometric Sensors

AGS performance with CNT Electro‐catalyst

CNT sensor response to varying concentrations 50 to 500 ppb. Linear regression R2 values is shown for 5 sensors.AGS is linear and HMOx is non-linear.

COMPARISON OF AGS & HMOxAGS is faster; HMOx has LDLt95 = 14 sec vs t95=132 secLDL = 140 ppb vs 0.57 ppb

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Compare selectivity:AGS has NO2 response, no RH or VOC response; 

HMOx has VOC and RH response but no NO2 response 

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HMOx has larger interference from VOCs & RH than AGS but AGS has larger interference from NO2 than HMOx

Sensor responses for O3 in H2O[simple porous Teflon barrier]

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Instruments: 1]wearable personal protection‐PO3;

2] DO3 – dissolved Ozone meter [not shown]3] Fixed‐site meter= sensor array [AGS+HMOx]with on‐board ozone calibration and zero filter.

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Pocket ozone!

KWJ/EcoSensor Division’s EZ‐10W Dissolved Ozone Monitor. This design would be basis for a low‐cost, lower‐end TTHM Monitor.  Dissolved ozone may be measured in the headspace abovethe water (on right); for TTHM, the sample bottle would be replaced with a module incorporating a membrane separator. 

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Left= chloropentafluorobenzene at 200ppb‐100 ppm; 

right= response time to TCE.L R

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Figure 6. (Left) R-Cl sensor response to chloropentafluorobenzene from 0.2 ppmv to 100 ppmv. (Right) Response to trichloroethylene with varying exposure time.

Important!    sensor is selective

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Figure 1: (Left) Response of the “R-Cl” sensor to hexane and carbon tetrachloride circa 1995.(note: the apparent response forhexane was due to a pneumatic error and slow response is due to test equipment not sensor). (Right): R-Cl sensor bead (amixture of lanthanum chloride and lanthanum oxide sintered in silica) mounted on a 2 cm diameter header.

Deployment in well–multi‐RCl sensors provide spatio‐temporal profiling.

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Well

Well Probe

Contamination 

Source

Plume

MEMS SENSORS MEMS recent work

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31

Can we design a MEMS structure to implement multiple chemistries and multiple classes of chemical sensors?

• Single process; Same physical design• Functional layer added as last step• One substrate made by the millions and used for 1000 different applications– Low power, Small size,  effective,  low cost, – reliable, specifically functionalized

• sensitive, selective, rapid response, stable, long‐lifetime.

Transient Measurement of Resistance of MEMS thermal element Sensor – collaboration with Prof. Hesketh, GIT

500 MHz OscilloscopeWith USB Port

SRS Signal Generator

Sensor

Rf = 100 ohm resistor

Ch1

Ch2

ground

3V

1uS

Channel 1 records voltage, and channel 2 records current

Sensor Resistancecalculated from:R(t) = [(V1(t)*Rf)/V2(t)]-Rf

Temperature vs resistance calibrated in separate experiment. Sensor in box purged with pure gas.

KWJ MEMS TCD sensor‐Mar 09[10‐100ns response time; power 0.6 nW/reading]

34

Sensor Output at 16 mA and 73.8 ºF[multiple T + Algorithm]

2500 ppm

500 ppm250 ppm1000 ppm

500 pp

5000 ppm4000 ppm2000 ppm3000 ppm

1000 ppm

2500 ppm500 ppm1000 ppm

 

35

Executive Summary 

Testing ConditionsCO2 Range1 0 ~ 5000 ppm

Relative Humidity (RH) Range 2

5% ~ 80% non-condensing

Heating Current3 12 mA 16 mA

Bridge Temperature 237 ºF 365 ºF

Results4

CO2 Sensitivity @ 73.8 ºF 12.8 μV / 100 ppm 26.3 μV / 100 ppm

CO2 Sensitivity @ 90.4 ºF 13.3 μV / 100 ppm 22.7 μV / 100 ppm

RH Sensitivity @ 73.8 ºF 50.2 μV / %RH (21 μV / 100 ppm) 101.8 μV / %RH (42.4 μV / 100 ppm)

RH Sensitivity @ 90.4 ºF 88.4 μV / %RH (17 μV / 100 ppm) 224.0 μV / %RH (43.9 μV / 100 ppm)

Noise 6 μV 21 μV

1. Customer requested 500 ppm to 2000 ppm2. Range limitation imposed by testing equipment. Sensor can operated from 0 to 100% RH non-condensing.3. Constant current provided by Dial-a-Source Model DAS 45 from General Resistance Instrument4. Sensor voltage output recorded by an Agilent 34970A Data Acquisition/Switch Unit

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37

Executive Summary (II)• Sensor signal shows a near linear relationship to CO2 and RH• CO2 and RH sensitivity vary depending on heating current (i.e. bridge temperature)• Measuring at 2 different heating currents allows for solving for CO2 and RH (or absolute 

humidity) • Sensitivity (CO2 and RH) and noise both increase with heating current, but noise increases at 

a faster pace• CO2 sensitivity shows little dependency on ambient temperature• RH sensitivity shows significant dependency on ambient temperature; This can be partially 

explained by the fact that sensor measures absolute humidity (not temperature dependent) while it is calibrated against relative humidity (temperature dependent)

MEMS will need to evolve new processes and materials capability if it is to play an important role in Chem‐Bio Sensors

KWJ SENSOR Production clean room

"The significant problems we face cannot be solved at the same level of thinking we were at when we created them."‐ A. Einstein

1821

2007

Metrology Expertise[KWJ characterizes sensor/instrument responses]

• Applications– Characterization– Validation– Benchmarking– Calibration– Tiered testing

• Capability– Facilities

• Clean room• SSTUF • Sensor production/cal• Instrument design/cal

– CSA, UL, CE, …

– Expertise• Analytical chemistry• Engineering• Sensor science

– Equipment• P’stat, spectrometers• Collaboration‐ICSSE…

Shared Sensor Testing User Facility

MEMS Gas Sensors

Conclusions• The CNT provides a robust, rapid, reversible electro‐catalyst and enables a practical nano‐sensor for O3

• Analytical characteristics of AGS are complementary to the HMOx and sensors can form synergistic array with performance similar to a UV spectrometer.– HMOx  LDL=0.1 ppb & AGS linear to > 200 ppm – Few false alarms: AGS faster, HMOx <<NO2 interference– Autocalibration and auto zero functions

• allow long time low maintenance use. 

• Expanded to HC and THMs in water.• MEMS SENSORS – superfast, low power, low cost,  sensitive, autocal, auto‐compensate.

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THANK YOU  from Joseph R. Stetter, KWJ, Newark CA and IIT, Chicago, IL USA

• Chemical‐/Bio‐/Gas‐Sensors– Ozone, CO, H2S, O2, CH4, combustible HCs,H2, …

• Instruments – In‐line , fixed, or Wearable• Applications engineering

– Sensor Systems– Nano‐enabled and MEMS sensors– Lower Power/Cost/Size 

• Nano‐Materials Research/Development• Sensor Characterization and Metrology • www.kwjengineering.com• www.ecosensors.com• www.detectcarbonmonoxide.com

What Can We Measure for You?

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KWJ ‐Markets Served

Markets Served:MedicalEnergy – “Green” AlternativesIndustrialHealth and SafetyConsumerFirst Responder –Fire, Police, ArsonHomeland Security, SurveillanceSensors – HVAC, IAQ, IndustryR&D – New Products• Custom products• New Capability

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Wearable protection from KWJ’s Pocket CO

• 0‐100% CH4 analyzer

• Vapor recovery stack gas combustibles monitoring

• Flare gas monitor for CH4‐mix to stack [20‐40% CH4]

• Remote, fixed‐site and portable H2S and toxics monitor– Sample draw detector assembly for CH4, O2, CO or H2S

• Mobile Combustible Gas Detection system for tank farms– Monitor and alarm during repairs, cleaning, painting operations

• Wearable/portable “POCKET” gas detector/monitor/dosimeters– Fire, police, first responder, building inspector, pilots, scuba, …– SATA under hood CO detection, …

• Complete line of OZONE in air and OZONE in water monitors

• R&D for military, government and industrial clients.

KWJ Gas Detection Products (continued)Instruments and Sensors: Low Cost / High Performance

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