Alan Schilowitz , Andy Riley, Dalia Yablon, Mark Disko ExxonMobil Research and Engineering Co. Corporate Strategic Research Laboratory Annandale, New Jersey Ultra-Sensitive Microsensors for Chemical Analysis

Why Microsensors ? High sensitivity Low power consumption Enables wireless Improved safety Redundancy Potential for large number of parallel sensors Portability Personal monitoring (e.g. badges) Small sample size

High sensitivity

Low power consumption

Enables wireless

Improved safety

Redundancy

Potential for large number of parallel sensors

Portability

Personal monitoring (e.g. badges)

Small sample size

How Many Cantilevers Can Fit on the Head of a Pin ? 2 mm Two Modes of Operation Dynamic Static

Two Modes of Operation

Dynamic

Static

Micro-Cantilevers Background Extension of Atomic Force Microscopy Some experiments carried out in Atomic Force Microscope head Ultrahigh sensitivity to mass change Use for chemical measurement pioneered by Thundat (ORNL) and Gerber (IBM Zurich) Applied to analysis of gas and aqueous solutions Cantilevers commercially available in variety of shapes and materials Range of resonant frequencies, spring constants, shapes Laser PSD Focusing Lens

Extension of Atomic Force Microscopy

Some experiments carried out in Atomic Force Microscope head

Ultrahigh sensitivity to mass change

Use for chemical measurement pioneered by Thundat (ORNL) and Gerber (IBM Zurich)

Applied to analysis of gas and aqueous solutions

Cantilevers commercially available in variety of shapes and materials

Range of resonant frequencies, spring constants, shapes

Dynamic Mode Increasing viscosity changes resonance spectrum Ultra sensitive to mass changes Cantilevers can be driven with piezo-electric crystal Mass build-up changes resonant frequency Viscosity change alters resonant frequency and width of spectrum Analysis in Dynamic Mode 0 2000 4000 6000 8000 10000 12000 Frequency (Hz) Amplitude Air Increasing Viscosity

Dynamic Mode

Increasing viscosity changes resonance spectrum

Ultra sensitive to mass changes

Cantilevers can be driven with piezo-electric crystal

Mass build-up changes resonant frequency

Viscosity change alters resonant frequency and width of spectrum

Cantilevers Respond to Viscous Damping High Q Low Q Increasing Viscosity Viscosity can also be measured by frequency change Less sensitive than Q Measurements can be made on micro liter samples

Viscosity can also be measured by frequency change

Less sensitive than Q

Measurements can be made on micro liter samples

Chemical Analysis in Static Mode Detection limit is in sub picogram range Selective adsorbant on one side only Untreated Cantilever Gold Coated Cantilever Detects Mercaptans Mercaptan Injection Static Mode - coated cantilevers respond to adsorption Detect deflection of cantilevers coated on one side

Detection limit is in sub picogram range

Static Mode - coated cantilevers respond to adsorption

Detect deflection of cantilevers coated on one side

Functionalized Cantilever Arrays for Aromatics Detection Self-Assembled Monolayers Impart Chemical Selectivity to Highly Sensitive Cantilever Transducers Self-Assembled Monolayer Candidates: SH Benzyl Mercaptan SH Naphthalenethiol SH OH Mercaptohexanol SH ( ) 6 Octadecanethiol

Cantilever Response To Aromatic Vapor Cantilevers exposed to aromatic vapor (parts per thousand) in laboratory air Treated cantilevers have unique response to aromatics S OH S S ( ) 6 S toluene xylene toluene xylene d. ODT - octadecanethiol c. MH - mercaptohexanol b. NT - naphthalenethiol a. BM – benzyl mercaptan toluene xylene toluene xylene

Cantilevers exposed to aromatic vapor (parts per thousand) in laboratory air

Treated cantilevers have unique response to aromatics

Summary Micro-Cantilever sensor applications Viscosity on micro-liter samples Potential for sub picogram chemical sensitivity Chemical specificity with Self Assembled Monolayers (SAM) Potential for applications where: Sample size is limited Large scale redundancy is desirable Low power consumption is necessary

Micro-Cantilever sensor applications

Viscosity on micro-liter samples

Potential for sub picogram chemical sensitivity

Chemical specificity with Self Assembled Monolayers (SAM)

Potential for applications where:

Sample size is limited

Large scale redundancy is desirable

Low power consumption is necessary

Medical Applications Light traces are before exposure to e-coli Dark traces are after exposure B. Illic et.al., Appl. Phys. Lett. 77 (3), 450 (2000) E-Coli Sensor Vibrational frequency reduced as cells bind to cantilever Frequency = W. Guanghua et.al., Nature Biotechnology 19 , 856 (2001) Prostate Specific Antigen (PSA) Sensor

Vibrational frequency reduced as cells bind to cantilever

Frequency =

References - Medical Applications Rapid and label-free nanomechanical detection of biomarker transcripts in human RNA Zhang, J.; Lang, HP.; Huber, F.; Bietsch, A.; Grange, W.; Certa, U.; McKendry, R . ; Guntherodt, HJ.; Hegner, M. & Gerber, Ch. Nature Nanotechnology , 1 , 214-220 (2006). Novel electrical detection of label-free disease marker proteins using piezoresistive self-sensing micro-cantilevers Wee KW, Kang GY, Park J, Kang JY, Yoon DS, Park JH, Kim TS Biosens Bioelectron 2005 Apr 15;20(10):1932-8 Array of Nano­Cantilevers as a Bio­Assay for Cancer Diagnosis Klein, K.M.; Jiantao Zheng; Gewirtz, A.; Sarma, D.S.; Rajalakshmi, S.; Sitaraman, K. Electronic Components and Technology Conference, 2005. Proceedings. 55th Volume , Issue , 31 May-3 June 2005 Page(s): 583 - 587 A Review of Microcantilevers for Sensing Applications Vashist, S.K., June 2007 www.azonano.com/details.asp?ArticleID=1927