1. M. Meyyappan
NASA Ames Research Center
Moffett Field, CA 94035
email: m.meyyappan@nasa.gov
Acknowledgements: Jing Li, Y. Lu, Jessica Koehne, Cattien
Nguyen,
Jeong-Soo Lee

2. Innovation: Breaking Stereotype
Since 1960 ~
SiO2(solid)
Gate high-k(solid) Fluid
S D Gate Gas/liquid
S D
• Solid-state Gate Dielectric
• Insolating gate to drain
“The guys like us who work with the <Fluid Gate Dielectric>
stuff every day consider silicon • Stimuli responsive fluid
dioxide the greatest gift from • Exchangeable
God ”, John S. Suehle, NIST • Drop-on-demand

3. Structure:Nanogap Gate Dielectric FET
Gate oxide
D Removal D
S S
Independent Double-Gate FinFET Nanogap Double-Gate FinFET
• Flexible threshold voltage • Radioresponsive liquid
- radiation sensor
• Low-power application
• Chemical responsive liquid
- gas sensor
• Bio responsive treatment
- bio sensor

4. Prototype of Nanogap FET
Liquid
Sol-Gel
DNA
Protein
4

5. PMDS: Radioresponsive Liquid
CH3
Polydimethylsiloxane (PDMS) CH3 CH3
-ray |
| | -Si-O-
|
-Si-O- -Si-O- CH3
| |
CH3
+  3
CH

CH3
CH3 CH3 |
| |
-Si-O- & H2 (gas)
-Si-O- & -Si-O- |
| | -ray CH2
*n=20 ~ 40 CH2 CH4 
 
-ray CH3
Radiation response of PDMS |
-Si-O- & CH4 (gas)
• Si-C, Si-O, C-H bond break 
• Charged radical creation Bonding Energy
• Cross-linking Si-C : 360 (KJ/mol)
• H2, CH4 release C-H : 413 (KJ/mol)
Si-O : 452 (KJ/mol)

6. Gamma-ray Detection
Gamma-radiation (C60)
VG Liquid
Gate
Ga
Drain 2.0
Source
1.5
Gate
Threshold voltage, VT (V)
1.0
VD 0.5
n
0.0
p
-0.5
-1.0

7. Biosensor

8. Bacteria DNA Protein
Insulating
Dielectrics
(optional)
e- e- e-
Electrical
contact Si wafer
Directly interface solid-state electronics with DNAs, RNAs, proteins, and microbes
in a miniaturized multiplex chip for quick detection(Lock and Key approach)

9. Nanoscale electrodes create a dramatic improvement in signal
detection over traditional electrodes
Traditional Macro- or Nanoelectrode
Electrode Micro- Electrode Array
Insulator
Nano-
• Scale difference between macro- • CNT tips are at the scale close Electrode
/micro- electrodes and molecules is to biomolecules
tremendous
• Dramatically reduced
• Background noise on electrode background noise
surface is therefore significant • Multiple electrodes result in
• Significant amount of target magnified signal and desired
molecules required redundance for statistical reliability.
X X
Candidates: SWNTs, MWNTs, Vertical
CNFs or Vertical SiNWs Source: Jun Li

10. Embedded CNT Arrays after
r. e.
Metal Film c. e. planarization
Deposition
w.
e.
Catalyst EC
Deposition
Plasma CMP
CVD TEOS
CVD
300 mm
30 dies on a 4” Si wafer 200 mm

11. Troponin Detection for Heart Disease
i
0.20
0.15
(a) bare electrode
Current/10 -6 A
0.10
5.00
g
0.00
-5.00
f
e
(b) bare / anti–cTnI electrode
d
-0.10 c
b
-0.15 a
0.8 0.6 0.4 0.2 0.0 -0.2 -0.4
Potential (V vs. SCE) curve c–g represent 0.25, 0.5,
-120 ii 1.0, 5.0, and 10.0 ng ml-1
-100 human cTnI antigen binding
-80
to the bare electrode after
Zim (kΩ)
-60 g
f
immobilization with anti–cTnI
-40 e
d
c
antibody respectively.
-20
b
a
0
0 15 30 45 60 75 90
Zre (kΩ)

12. WHY: Effective Clinical Technique
• DBS has been clinically effective in the treatment of
movement disorder
HOW: Four Interrelated Hypothesis
• Paradox of similar effects to lesioning of target structure is
explained by the following:
-Depolarization Blockage
-Synaptic Inhibition
-Synaptic Depression
-Stimulation Induced Modulation of Pathways
PROBLEMS: Indiscriminate Activation
• Stimulation indiscriminately affects all tissue around the
electrode (size: 1.27mm diameter with four 1.5mm contacts)
• Crude method without feedback
IMPROVEMENTS:
Targeted Activation to specific location down to sub mm scale
Obtain feedback information – such as neurotransmitter
levels
Medtronic

13. Discrimination of Dopamine, Serotonin and
Ascorbic Acid
a) Baseline-corrected DPV plots of individual
detection of 10 µM DA, 1 mM AA, and 10
µM 5-HT with a glassy carbon electrode
b) Background subtracted DPV plots of
individual detection of 10 µM DA, 1 mM AA,
and 10 µM 5-HT with a carbon nanofiber
electrode
c) Baseline-corrected DPV plots of a ternary
mixture of 10 uµM DA, 1 mM AA, and 10
µM 5-HT with a glassy carbon electrode
d) Baseline-corrected DPV plots of a ternary
mixture of 10 uµM DA, 1 mM AA, and 10
µM 5-HT with a carbon nanofiber electrode
e) Baseline-corrected DPV plots of a ternary
mixture of 1 mM AA, 10 µM DA, and 5-HT
(10 µM, 5 µM, 2.5 µM, 1 µM, 0.5 µM, 0.25
µM) with a carbon nanofiber electrode
f) Baseline-corrected DPV plots of a ternary
mixture of 1 mM AA, 10 µM 5-HT, and DA
(10 µM, 5 µM, 2.5 µM, 1 µM, 0.5 µM, 0.25
µM, 0.1 µM) with a carbon nanofiber
electrode

14. (a) and (b) : EIS spectra with an antibody probe
(c) and (d) : with an aptamer probe
(b) and (d) use control targets

15. Rct decreases after washing with elution buffer and returns to a similar value to the
aptamer functionalized chip, i.e. the ricin protein is washed away but the aptamer probe
remains bound to the VACNFs. Upon reintroduction to ricin, Rct increases to a value
similar to the original ricin-bound EIS curve. Thus, the aptamer retains its bioactivity and
is able to be regenerated, thus indicating the reusability of the aptamer based biosensor.

16. 300 mm
200 mm
Potential applications:
30 dies on a 4” Si wafer (1) Lab-on-a-chip applications
(2) Early cancer detection
The electronic chip needs to (3) Infectious disease detection
be integrated with (4) Environmental monitoring
microfluidics for sample (5) Pathogen detection

17. Chemical Sensor

19. • First, a single device has no value. We need a system consisting of:
- Sensor array (Electronic Nose, Pattern recognition…)
- Pre-concentrator ?
- Sample delivery, Microfan? Jet?
- Signal processing chip
- Readout unit (data acquisition, storage)
- Interface control I/O
- Integration of the above (Nano-Micro-Macro)
• Criteria for Selection/Performance
- Sensitivity (ppm to ppb as needed)
- Absolute discrimination
- Small package (size, mass)
- Low power consumption
- Rugged, reliable
- Preferably, a technology that is adaptable to different platforms
- Amenable for sensor network or sensor web when needed

20. • Compared to existing systems, potential exists to improve sensitivity
limits, and certainly size and power needs
• Why? Nanomaterials have a large surface area. Example: SWCNTs
have a surface area ~1600 m2/gm which translates to the size of a
football field for only 4 gm.
• Large surface area large adsorption rates for
gases and vapors changes some measurable
properties of the nanomaterial basis for
sensing
- Dielectric constant
- Capacitance
- Conductance
-
-
4 grams

21. • Easy production using simple microfabrication
• 2 Terminal current-voltage measurement
• Low energy barrier - Room temperature sensing
• Low power consumption: 50-100 µW/sensor
Processing Steps
1. Interdigited microscale
electrode device fabrication
2. Disperse purified nanotubes
in DMF (dimethyl
formamide)
3. Solution casting of CNTs
across the electrodes
Jing Li et al., Nano Lett., 3, 929 (2003)

22. • Test conditions:
Flow rate: 400 ml/min
Temperature: 23 oC
Purge & carrier gas: N2 , Air
• Measure response to various
concentrations, plot
conductance
change vs. concentration
• Sensor recovery can be
speeded up
by exposing to UV light, heating
Detection limit for NO2 is 4 ppb. or

23. • Use of a sensor array (32-256
sensors)
• Variations among sensors
- physical differences
- coating
- doping
- nanowires Operation:
1. The relative change of current or
resistance is correlated to the
concentration of analyte.
2. Array device “learns” the response
pattern in the training mode.
3. Unknowns are then classified in the
identification mode.
4. Sensor can be “refreshed” using UV
LED, heating or purging

24. Analyte Sensitivity/Detection Limit
CH4 1 ppm in air
Hydrazine 10 ppb tested by KSC
NO2 4.6 ppb in air
NH3 0.5 ppm in air
SO2 25 ppm in air
HCl 5 ppm in air
Formaldehyde 10 ppb in air tested by JPL
Acetone 10 ppm in air
Benzene 20 ppm in air
Cl2 0.5 ppm in air
HCN 10 ppm in N2
Malathion Open bottle in air
Diazinon Open bottle in air
Toluene 1 ppm in air
Nitrotoluene 256 ppb in N2
H2O2 3.7 ppm in air
DMMP 100 ppb in air

25. 2nd
1st expos
expos ure
ure
3rd 4th
exposure
exposure
• Pristine, Rh-loaded and PEI-
Gaps
functionalized SWCNT: all give fast Fingers
response ~18 seconds
• Recovery time ~1 min
• Detection limit: 10-20 ppb

26. H2O2
• Fast sensor response: 6 seconds
• Detection limit: 25 ppm
Mechanisms?
polyethyleneimine (PEI)-functionalized •Electron donation from an
SWCNTs oxidizer like H2O2 decreases the
• Headspace test: sensor exposed to conductivity of the inherently p-
open bottles of H2O2, water, and type SWCNTs in air
methanol
•PEI-functionalized SWCNTs have
• Substantial difference in responses been shown to be n-type. Their
conductivity increases after
• Adequate to construct e-nose with exposure to H2O2
32-sensor elements

27. A 32-channel sensor chip (1cm x 1cm)
with different nanostructured materials
for chemical sensing
5”
NASA Ames chemical sensor module was
on a secondary payload of a Navy
satellite (Midstar-1) that was launched
via Atlas V on March 9, 2007. The nanosensor module (5”x 5”x 1.5”) contains
a chip of 32 sensors, a data acquisition
board, sampling system, and a tank with
20ppm NO2 in N2.

28. 1. Temperature
data
2. Humidity data
3. Pressure data
4. Altitude data
9. Chemical ID
Sensor state and concentration
5. Sensor state
Pump condition
8. Pump state
Pump location 7. Sensor settings
6. App information

31. • Some diseases have specific markers which show up in
excess concentration in the breath of sick people relative
to normal population.
Examples: Acetone in diabetes patients
NO in asthma patients
•In these cases, simple chemical sensors (gas/vapor sensing) with
pattern recognition can be valuable.

32. Room Temperature Sensing of Acetone
• ZnO nanoparticles show a good response to 1-50 ppm at room temperature
• Humidity effects are important and have been investigated
• ZnO NP is a useful candidate to include in the sensor array for providing reliable
patterns

33. • Emerging of nano will NOT eclipse micro or MEMS
• Indeed, in many cases (but not all), nano-based products would need
MEMS to achieve desirable performance goals. This means,
hierarchical
Nano - Micro - Macro Integration
• Nanotechnology, if it succeeds in the market place, will breathe new life
and renewed vigor into the MEMS (research, applications,
infrastructure, fabs, products, market, companies, profit…..)
• We have discussed some examples, in terms of chemical
and bio sensors , where the “heart and soul” of the system
is
a nanomaterial, or some nano phenomena and the system
itself needs a seamless integration to micro/macro for a
technically feasible and commercially viable product.