Nanosensors for structural monitoring in civil engineering · Nanosensors and civil enginnering Monitoring pore sizes with ultrasounds Monitoring pore humidity with CNTFET Concrete

Nanosensors and civil enginneringMonitoring pore sizes with ultrasounds

Monitoring pore humidity with CNTFET

Nanosensors for structural monitoring in civilengineering

New insight on promising carbon nanotubes devices

B. Lebental1 F. Bourquin1 E. Norman2 C. S. Cojocaru2

A. Ghis3

1Universite Paris-EST, IFSTTAR, Paris, 75015, FRANCE

2LPICM, Ecole Polytechnique, Palaiseau, 91128, France

3CEA-LETI, Minatec Campus, Grenoble, 38000, FRANCE

NDCM-XII

[email protected] Nanosensors in civil engineering1/14



Nanotechnologies in the construction sector : why ?

Nanotechnologies :

Already plenty of (niche)productsGlobal market : 2500 B$ in2015

⇒ Goal : finding large marketopportunities

Construction sector :

More than 10 % of EuropeanGDPToward ’green’ construction(and cost reduction)

⇒ A new priority : improvingstructural service expectancy

Market of nanotechnologies 1Green roofing

1. Lux Research Inc., 2010




Concrete materials : degradations and durability

1. Baroghel-Bouny, Tech. Ingenieur, 2005

[email protected] Nanosensors in civil engineering

Various degradation processes

Corrosions, cracks, swelling...Origin : particules and gas transport within microporosity

⇒ To control durability, one needs tomonitor continuously microporosity

Degradations caused by internal swelling 1

Concrete microporosity

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Monitoring microporosity with nanosensors

Current monitoring solutions : large sensors with mmresolution at best

⇒ Challenge : to obtain pore by pore (µm) resolution⇒ Solution : Monitoring with 1 µm size nanosensors

We consider two parameters varying during service lifePore size : 10 nm to 10 µmHumidity : 70 % to 100 % relative humidity (RH)

⇒ determine gaseous/ionic transport parameters ⇒ Durability




Carbon nanotubes based ultrasonic transducer

Device concept : µ-cMUT 1 :Vibrating membrane of aligned carbon nanotubes1 µm size ⇒ 10 times smaller than existing US transducers

⇒ How does ultrasonic monitoring work at the microscale ?

⇒ How does one prototype a US microtransducer ?

1. B. Lebental et al., 2008, Patents EN 08 57927 and EN 08 57928




Device modelling

Numerical identification of the quantities the µ-cMUT mightbe sensitive to :

Original elasto-acoustic problem in microfluidics 1

⇒ Development of an original numerical method 2

1. Beltman, J. Sound Vib., 227, 555-586, 1999

2. Lebental and Bourquin, J. Sound Vib., submitted 2009




Device modelling

Numerical identification of the quantities the µ-cMUT mightbe sensitive to :

Original elasto-acoustic problem in microfluidics 1

⇒ Development of an original numerical method 2

1. Beltman, J. Sound Vib., 227, 555-586, 1999

2. Lebental and Bourquin, J. Sound Vib., submitted 2009




Elasto-acoustic problem

2D non-adimensionnal fluid-structure problem (well-posed) :

Clamped plate in small displacement : d s

Convection-less, flow-less newtonian fluid : (p,uf )

1A∂tp + div uf = 0 sur Ω

Mass conservation∂tuf = − 1

M2 grad p + 1Re2,r

grad div uf + 2Rer

div e(uf ) sur Ω

Momentum conservation−g1d

s + ap∂ttds + rp∂yyyyd

s = g0 + n.σ(p,uf ).n sur Γs

Plate equationuf

y = 0 and ufx = ∂td

s sur Γs

Dirichlet boundary conditionuf = 0 sur Γf

Dirichlet boundary conditiond s(0) = d s(1) = ∂yd

s(0) = ∂yds(1) = 0 + C .I .

Clamped plate boundary condition




Our sensor concept : a microsonar

In air : large amplitude ; low sensitivity to geometry

In water : low amplitude BUTHigh sensitivity to depth : f1 ∝ l−1 1

Even with other variable parameters (width, rugosity...)

⇒ A microsonar : Measurement of water-filled pore depth

⇒ Monitoring of content and size of micropores

1. Lebental et al., EJECE 2011, 4, 649-662




Prototyping our microsonar


Aligned deposition of SWNT

SWNT anchoring

Membrane release

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Applicative relevance

Ultra-thin membranes ⇒ good sensitivity to pore features

Large amplitude of vibrations measured ⇒ good transductionefficiency

⇒ Good candidate for in-situ monitoring of pore size




Carbon nanotubes field-effect transistor

Nanotube network as semi-conducting channel of a transistorFabricated by low-density deposition of SWNT on an insulatoratop gate electrodeCNTFET known to be highly sensitive to humidity :a drawback for electronics, an opportunity to us

⇒ CNTFET humidity sensor for micropores




Hysteresis sensitivity to humidity


Electrical features reproducibly sensitive to humidity

Ion, Ioff , Hysteresis,...Attributed to adsorption on silicon and on metalEspecially at high humidity

⇒ Well suited for high RH environment such as concrete

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Conclusions

Fabrication and evaluation of two promising sensing elementsVibrating CNT membranes for ultrasonic micropore monitoringCNTFET for humidity measurements in micropores

⇒ Two examples among various novel sensing opportunitiesProspects :

Integration into embeddable sensing units : smart aggregatesBenchmarking in the target environment : project Sense-citya real-scale benchmarking facility to be available in the nextfew years for (your ?) sensors dedicated to urbanmeasurement : buildings, infrastructures, networks...




Acknowledgments

Thank you for your attention !

Thanks to all my coworkers !

CEA-LETI, Minatec : Anne Ghis, Jean-Marc Fabbri, NawresSridi, Ariane Meguekam Sado, Philippe Renaux, NicolasCHevalier, Elisabeth Delevoye, Jean-Christophe GabrielLPICM, Ecole Polytechnique (+NanoCarb) : Evgeny Norman,Costel Cojoacaru, Louis Gorintin, Paolo BondavalliIFSTTAR Paris (LCPC) : Frederic Bourquin, Jean-MarieCaussignac


Documents

Nanosensors for structural monitoring in civil engineering · Nanosensors and civil enginnering Monitoring pore sizes with ultrasounds Monitoring pore humidity with CNTFET Concrete