E lectrical & M echanical characteristics of DNA bundles revealed by S ilicon N anotweezers

Lyon, France June 12, 2007 | Christophe Yamahata

Electrical & Mechanical characteristics of

DNA bundles revealed by

Silicon Nanotweezers

C. Yamahata, T. Takekawa,

M. Kumemura, M. Hosogi, G. Hashiguchi,

D. Collard & Hiroyuki Fujita

The University of TokyoInstitute of Industrial Science

Kagawa UniversityFaculty of Engineering


Electrical & Mechanical characteristics of DNA bundlesrevealed by Silicon Nanotweezers

Scope of the research

Working principle & Microfabrication of the Silicon Nanotweezers

DNA trapping by dielectrophoresis

Electrical & Mechanical characterization of DNA bundles

Conclusion & Outlook





Biophysical tools used for molecular manipulation

• Optical tweezers • Magnetic tweezers • AFM probes

* D. Collard et al., IEEJ Trans 2: 262–271, 2007















and

• Silicon nanotweezers



Working principle& Microfabrication

of the Silicon Nanotweezers

• Working principle• Microfabrication technology


Working principle of the Silicon Nanotweezers

External dimensions:4.5 mm × 5.5 mm

SOI wafer The different elements are:

• Electrically insulated• Mechanically locked with each other





Differential capacitive sensor



Differential capacitive sensor

MS3110 Universal Capacitive Readout™ (Irvine sensors, CA, USA)


Working principle& Microfabrication

of the Silicon Nanotweezers

• Working principle• Microfabrication technology


(1) Si3N4 deposition (LPCVD) + patterning(2) Silicon etching (RIE)(3) SiO2 oxidation (LOCOS)(3) SiO2 oxidation (LOCOS) + Si3N4 removal(4) KOH anisotropic etching of Silicon <111> facets

Microfabrication technology

(5) HF removal of buried oxide

Si

Si3N4

SiO2

(6) Backside etching by deep-RIE (with Al mask)

SOI wafer

• (100)-Si layer: 25 µm

• Oxide layer: 2 µm

• Handling wafer: 380 µm



Si

Si3N4

SiO2

(1)

(2)

(3)

(4)

(5)

(6)

SOI wafer

• (100)-Si layer: 25 µm

• Oxide layer: 2 µm

• Handling wafer: 380 µm




DNA trappingby dielectrophoresis


DNA trapping by dielectrophoresis (DEP)

Droplet:• λ-DNA: 12 nmol/L• DI water: 5 µL

Dielectrophoresis (DEP): 30 sec @ 1 MHz, 40 Vpp (20 µm gap)


λ-DNA bundle20 µm gapdiameter ~ 380 nm

DNA trapping by dielectrophoresis (DEP)


Electrical & Mechanical characterization

of DNA bundles

• Electrical characterization• Mechanical characterization


Humidity generator

Ambient air Pump

Gas washing

bottle

Mixer

Temperature and humidity sensor

Glove box

Faraday cage

Keithley 6487 Picoammeter / Voltage Source

chassis

desiccant

saturator

Electrical characterization of DNA bundles

Experimental setup



~ 20 GΩ

~ 5 TΩ

Measurements for different DNA bundles diametersQuasi-ohmic behavior

Measurements on “wet” DNA bundles

(various diameters)

T = 25 °C rh ~ 55% humidity


Measurements on “wet” DNA bundles

(various diameters)

Conductivity bundle section


Measurements for different DNA bundles diametersEffect of DNA bundle diameter



Effect of humidityExponential dependence with relative humidity

Transient current recording for a 5V step.

Data recorded at 21 °C (1°C overall fluctuation) for different humidity levels (rh 0.2% for each curve)



Effect of humidityExponential dependence with relative humidity

Data extracted from previous measurements (5V step) after 60 sec. (rh was decreased from 75% to 45% in 6 hours)


Electrical & Mechanical characterization

of DNA bundles

• Electrical characterization• Mechanical characterization


Mechanical characterization of DNA bundles

Displacement: ~ 3 µm Cmax 200 fF

Sensitivity: 2 V/pF 150 mV/µm

Error: ε <1 mV

5 nm resolution

Characterization of empty tweezersMeasurements performed with the MS3110 Universal Capacitive Readout™


Sensitivity of the capacitive sensor enables the measurement of few nN forces

(single DNA ~ 80 pN)

Bundle stretching can be observed

Mechanical characterization of DNA bundles

Measurements after DNA bundle trappingMeasurements performed with the MS3110 Universal Capacitive Readout™





• Efficient trapping of DNA by dielectrophoresis

• Extensive electrical characterization of DNA bundles

• Displacement: 2-3 µm range / few nm resolution

• Force: few nN sensitivity

High potential for biophysical characterization of long macromolecules. e.g.: DNA bundle, microtubules, actin filament, etc.

A new type of biophysical tool has been proposed:


Acknowledgments


Swiss National Science Foundation (SNSF)

Japan Society for the Promotion of Science (JSPS)

Japan Science and Technology Corporation (JST)

Centre National de la Recherche Scientifique (CNRS)

Acknowledgments


Thank you for your attention.Thank you for your attention.

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