MEMS2014 Conference Presentation Dominik Ziegler

1. ENCASED CANTILEVERS FOR LOW-NOISE FORCE
AND MASS SENSING IN LIQUIDS
Dominik Ziegler PhD
Material Science Division, Molecular Foundry, Lawrence Berkeley National Laboratory

2. High Resolution
Imaging of Mica
Encased Cantilevers
Fabrication
Quantitative Mass Sensor
Gentle Imaging of
Lipid Bilayers
Interferometric
Deflection Detection
Dominik Ziegler PhD
Material Science Division, Molecular Foundry, Lawrence Berkeley National Laboratory

3. VISCOUS DAMPING LIMITS RESOLUTION
Fn

4k BTk
0Qi
4k BTb
Force Noise  Smallest Measurable Force
ω0≈150 kHz
Q≈200
ω0≈50 kHz
Q≈4
Fn air≈15fN/√Hz
Fn water ≈200fN/√Hz
100 m long, 30 m wide

High forces deform soft samples and limits resolution

4. LET`S GO SCUBA DIVING!

5. FABRICATION OF ENCASED CANTILEVERS
-Length of levers can be tuned
-Tip’s sharpness is maintained

6. FABRICATION OF ENCASED CANTILEVERS
-Length of levers can be tuned
-Tip’s sharpness is maintained

7. ENCASED CANTILEVER IN AIR/WATER
air
water
fair=310.280kHz
fwater=309.71kHz
Qair=210
Qwater=133
Single clean resonance peak.
High Q and high frequency, performance as in air (Fn=12 fN/sqrt(Hz))
-Only small frequency shift (1%)  No Added Mass
-Viscous damping of tip (few um) and double sided squeeze film damping

8. GENTLE IMAGING OF LIPID BILAYERS
height of supported DPPC
bilayers on mica
softest possible imaging
amplitude modulation
“Hydra Levers” by AppNano
Encased silicon lever (Mikromasch NSC36)
L = 200 µm, k=0.084N/m f=17 kHz
l =110 µm, k = 0.95N/m, f=85kHz
Thicker measured height
 Less deformation by tip

9. HIGH-RESOLUTION IMAGING OF MICA IN LIQUID
0.5 nm
MICA lattice using amplitude modulation
300mM KCl, 10mM K2HPO4, 5 lines/s
Unmodified commercial instrument
Multimode, Bruker

10. OSCILLATORY HYDRATION FORCE
Amplitude[mV]
Amplitude [Å]
(WATER STRUCTURE ON MICA)
20
15
10
5
0
0
1
0
1
Phase [Deg]
Phase[Deg]
60
3
2
[nm]
2
3
0.5 nm
40
20
0
-20
[nm]
~4Å
Ultra-small amplitude
displacement of the last few water layers
single curve no averaging
Kobayashi, J. CHEM. PHYS. 138, 184704 (2013)

11. QUANTITATIVE MASS SENSING WITH ENCASED CANTILEVERS
Indirect measurement of mass over
surface stress (DC measurement)
0
Known location of added mass  quantitative mass sensor
2

12. QUANTITATIVE MASS SENSING WITH ENCASED CANTILEVERS
250 nm Gold Particles
mc = 22.88ng
ne =
1
1
= 4 » 0.23
(bi L)4 Ci
Rp = -14.8mHz/fg
Known location of added mass  quantitative mass sensor

13. QUANTITATIVE MASS SENSING WITH ENCASED CANTILEVERS
250 nm Gold Particles
mc = 22.88ng
ne =
1
1
= 4 » 0.23
(bi L)4 Ci
Rp = -14.8mHz/fg
Cantilever Based Mass Sensing
mavg= 168 ± 12 fg
TEM Based Estimation
mavg= 175 ± 68 fg
Theory Gold Sphere
m=157 fg

14. SMALLEST DETECTABLE MASS
Current Cantilever Design
l = 125m m
w = 30m m
h = 2.5m m
k 10 N m
0
220kHz
A =100nm
Q 317
dm = 0.1fg / Hz » 60MDa / Hz
Optimized for Mass Sensing
l = 25m m
k = 1700 N m
w = 5m m
h = 5m m
w 0 = 11.0MHz
A =100nm
Q = 4500
dm = 20zg / Hz » 12.5kDa / Hz
Single Very Small Protein
(~100 Carbon-12 Atoms)
~60 Gold Atoms
Each 0.32 zg

15. SMALLEST DETECTABLE MASS
Current Cantilever Design
l = 125m m
w = 30m m
h = 2.5m m
k 10 N m
0
220kHz
A =100nm
Q 317
dm = 0.1fg / Hz » 60MDa / Hz
Optimized for Mass Sensing
l = 25m m
k = 1700 N m
w = 5m m
h = 5m m
w 0 = 11.0MHz
A =100nm
Q = 4500
dm = 20zg / Hz » 12.5kDa / Hz
Single Very Small Protein
(~100 Carbon-12 Atoms)
~60 Gold Atoms
Each 0.32 zg

16. INTERFEROMETRIC READOUT
Destructive interference if path
length difference (δ) between two
beams is
Finesse F= δλ/Δλ
Detect intensity of reflected light
(Single photodiode, high BW 50MHz)
k=45N/m
f0=320kHz
F=δλ/Δλ
Finesse ~3
Position Noise ~6fm/√Hz! (@10.6mW,~770nm)

17. CONCLUSION
Encased cantilevers overcome the problem of
viscous damping in liquids
Compatible with commercial instruments
-Ultra-low force noise in liquids 12 fN/sqrt(Hz)
-Gentle and High-Resolution Imaging
-Water Hydration Layers
-Quantitative Mass Sensor 0.1 fg/sqrt(Hz)
-Interferometric Readout 6 fm/sqrt(Hz)

18. ACKNOWLEDGEMENTS
Paul D Ashby
Interferometric Readout
Adrian Nievergelt (EPFL, Switzerland)
Technical Support
Ed Wong, Virginia Altoe
Preparation of Lipid Bilayers
David Chmielewski (UC Berkeley)
Modeling of Squeeze Film Damping
Dara Badri (UC Berkeley)
Aram Klaassen (University of Twente, The Netherlands)
Frieder Muegele (University of Twente, The Netherlands)
John Sader (University of Melbourne, Australia)
National Science Foundation
Cyber-enabled Discovery and Innovation #CBET940417
www.foundry.lbl.gov
www.scubaprobe.com
US Department of Energy DOE
#DE-AC02-05CH11231
www.lbl.gov
For more information please contact Dominik Ziegler PhD, dziegler@lbl.gov, +1 510 599 4444