Nanosensors for structural monitoring in civil engineering

Transcription

1 Nanosensors for structural monitoring in civil engineering New insight on promising carbon nanotubes devices B. Lebental 1 F. Bourquin 1 E. Norman 2 C. S. Cojocaru 2 A. Ghis 3 1 Université Paris-EST, IFSTTAR, Paris, 75015, FRANCE 2 LPICM, Ecole Polytechnique, Palaiseau, 91128, France 3 CEA-LETI, Minatec Campus, Grenoble, 38000, FRANCE NDCM-XII 1/14

2 Nanotechnologies in the construction sector : why? Nanotechnologies : Already plenty of (niche) products Global market : 2500 B$ in 2015 Goal : finding large market opportunities Construction sector : More than 10 % of European GDP Toward green construction (and cost reduction) A new priority : improving structural service expectancy Market of nanotechnologies 1 Green roofing 2/14 1. Lux Research Inc., 2010

3 Concrete materials : degradations and durability Various degradation processes Corrosions, cracks, swelling... Origin : particules and gas transport within microporosity To control durability, one needs to monitor continuously microporosity Degradations caused by internal swelling 1 Concrete microporosity 3/14 1. Baroghel-Bouny, Tech. Ingénieur, 2005

4 Monitoring microporosity with nanosensors Current monitoring solutions : large sensors with mm resolution at best Challenge : to obtain pore by pore (µm) resolution Solution : Monitoring with 1 µm size nanosensors We consider two parameters varying during service life Pore size : 10 nm to 10 µm Humidity : 70 % to 100 % relative humidity (RH) determine gaseous/ionic transport parameters Durability 4/14

5 Carbon nanotubes based ultrasonic transducer Device concept : µ-cmut 1 : Vibrating membrane of aligned carbon nanotubes 1 µm size 10 times smaller than existing US transducers How does ultrasonic monitoring work at the microscale? How does one prototype a US microtransducer? 5/14 1. B. Lebental et al., 2008, Patents EN and EN

6 Device modelling Numerical identification of the quantities the µ-cmut might be sensitive to : Original elasto-acoustic problem in microfluidics 1 Development of an original numerical method 2 6/14 1. Beltman, J. Sound Vib., 227, , Lebental and Bourquin, J. Sound Vib., submitted 2009

7 Device modelling Numerical identification of the quantities the µ-cmut might be sensitive to : Original elasto-acoustic problem in microfluidics 1 Development of an original numerical method 2 6/14 1. Beltman, J. Sound Vib., 227, , Lebental and Bourquin, J. Sound Vib., submitted 2009

8 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, u f ) 1 A tp + div u f = 0 sur Ω Mass conservation t u f = 1 M grad p Re 2,r grad div u f + 2 Re r div e(u f ) sur Ω Momentum conservation g 1 d s + a p tt d s + r p yyyy d s = g 0 + n.σ(p, u f ).n sur Γ s Plate equation uy f = 0 and ux f = t d s sur Γ s Dirichlet boundary condition u f = 0 sur Γ f Dirichlet boundary condition d s (0) = d s (1) = y d s (0) = y d s (1) = 0 + C.I. Clamped plate boundary condition 7/14

9 Our sensor concept : a microsonar In air : large amplitude ; low sensitivity to geometry In water : low amplitude BUT High sensitivity to depth : f 1 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 8/14 1. Lebental et al., EJECE 2011, 4,

10 Prototyping our microsonar Aligned deposition of SWNT SWNT anchoring Membrane release 9/14

11 Applicative relevance Ultra-thin membranes good sensitivity to pore features Large amplitude of vibrations measured good transduction efficiency Good candidate for in-situ monitoring of pore size 10/14

12 Carbon nanotubes field-effect transistor Nanotube network as semi-conducting channel of a transistor Fabricated by low-density deposition of SWNT on an insulator atop gate electrode CNTFET known to be highly sensitive to humidity : a drawback for electronics, an opportunity to us CNTFET humidity sensor for micropores 11/14

13 Hysteresis sensitivity to humidity Electrical features reproducibly sensitive to humidity I on, I off, Hysteresis,... Attributed to adsorption on silicon and on metal Especially at high humidity Well suited for high RH environment such as concrete 12/14

14 Conclusions Fabrication and evaluation of two promising sensing elements Vibrating CNT membranes for ultrasonic micropore monitoring CNTFET for humidity measurements in micropores Two examples among various novel sensing opportunities Prospects : Integration into embeddable sensing units : smart aggregates Benchmarking in the target environment : project Sense-city a real-scale benchmarking facility to be available in the next few years for (your?) sensors dedicated to urban measurement : buildings, infrastructures, networks... 13/14

15 Acknowledgments Thank you for your attention! Thanks to all my coworkers! CEA-LETI, Minatec : Anne Ghis, Jean-Marc Fabbri, Nawres Sridi, Ariane Meguekam Sado, Philippe Renaux, Nicolas CHevalier, Elisabeth Delevoye, Jean-Christophe Gabriel LPICM, Ecole Polytechnique (+NanoCarb) : Evgeny Norman, Costel Cojoacaru, Louis Gorintin, Paolo Bondavalli IFSTTAR Paris (LCPC) : Frédéric Bourquin, Jean-Marie Caussignac 14/14