magnetically- and bacteria-actuated mobile micro-robots · 2015. 10. 14. · micron scale mobile...
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© Metin Sitti, MPI/CMU
Magnetically- and Bacteria-Actuated Mobile Micro-Robots
Director, MPI for Intelligent Systems, Stuttgart, Germany
Professor, Carnegie Mellon University, Pittsburgh, USA
21 November 2014
© Metin Sitti, MPI/CMU
Outline
• Introduction
• Bacteria Propelled Swimming Micro-Robots • Magnetically Actuated Micro-Robots
• Conclusions
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© Metin Sitti, MPI/CMU
Small Scale Perception, Control and Action
An Amoeba during Phagocytosis
© Metin Sitti, MPI/CMU
Small Scale Biological Coordination and Swarming
S. Pratt, ASU Collective food retrieval by ant teams
H. Berg, Harvard Swarming of Salmonella typhimurium
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© Metin Sitti, MPI/CMU
Characteristics of Micro-Robots • Small scale physics and dynamics:
– Increased surface area to volume (S/V) ratio:
• Surface forces/drag/friction >> Inertial forces – Sticky & dissipative world!
• Fluidics: low Reynolds number (Re) – Inherently nonlinear, fast and stochastic dynamics – More sensitive to disturbances
S/V = 10-4 /mm Re = 108
0.4 body length/sec
S/V = 103 /mm Re = 10-4
30-50 body length/sec
1 µm
~2 m
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2−∝∝ L
L
L
V
S
• Limited everything on-board (actuation, power, computing, communication, sensing)
• New design, fabrication and control methods
© Metin Sitti, MPI/CMU 10 cm 1 cm 1 mm 100 µm 10 µm
Our Miniature Mobile Robot Portfolio
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Micron Scale Mobile Robots?
Challenge:
*M. Sitti, Nature 458, 1121, April 2009 (News & Views)
Miniaturization limitations on on-board power source & actuation*
© Metin Sitti, MPI/CMU On-Board Actuation Approach: Cell-Actuated (Self-Propelled)
Bio-Hybrid Micro-Robots • Harvesting the motility of cells to actuate micro-systems • Chemical energy inside the cell
Nature Comm. (2014)
Adv. Mat. (2014)
APL (2007), PNAS (2005), Biophys. J. (2004), …
R. Carlsen & M. Sitti, Small, on-line published (2014)
Nature Materials, 4 (2005)
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Selected Bio-Actuator: Serratia Marcescens Bacterium
• Speed: ~30 µm/s
• Sticks to surfaces with their cell body
• Chemotactic
Kwangshin Kim Science Photo Library Howard Berg
Harvard Univ.
© Metin Sitti, MPI/CMU
Attaching Bacteria to a 10 µm Polystyrene Bead
Blotting on the culture plate
B. Behkam and M. Sitti, Appl. Phys. Lett., 90, 23902 (2007)
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Bacteria Attachment Density Control
Attachment Time
Attachment Density
(Bacteria/µm2)
Sample Size
# of Bacteria on 10 µm bead
30 sec 0.17 1 54
1 min 0.35 ± 0.14 10 111 ± 45
5 min 0.47 ± 0.14 7 149 ± 44
10 µm 10 µm 10 µm
30 sec 1 min 5 min
Representative Images for different attachment times:
© Metin Sitti, MPI/CMU
Stochastic 3D Bead Translation & Rotation
MD : rotational drag on the bead FD : translational drag on the bead Fb : bacteria propulsive force
Motion parameters: • Flagella run and tumble rates • Flagella propulsion force & torque • Flagella hook flexibility & orientation • Bacteria number & surface distribution • Bead radius • Neighboring flagella microfluidic coupling? • Neighboring bacteria communication?
Hook
V. Arabagi, B. Behkam, E. Cheung, & M. Sitti, J. Appl. Phys. 109, 114702 (2011)
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3D Motion Tracking from 2D Images using Light Diffraction
Calibration images
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Different 3D Motion Patterns Near vs. Away From the Surface
Away from the glass slide Near the surface
5 micron beads
M. Edwards, R. Wright, & M. Sitti, Appl. Phys. Lett. 102(14), 143701 (2013)
Spiral motion of single bacterium attached beads away from surface: Bacterium torque/force measurement
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Steering Control using Chemotaxis?
Chemoattractant (L-aspartate) Diffusion
Bacteria attached beads moving towards chemical attractant gradients?
© Metin Sitti, MPI/CMU
Uniform Chemical Gradient Generation
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Chemotactic Behavior of Unpatterned Beads
10 µm bead, 2.5x speed
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2D Motion Trajectories No Chemoattractant Chemoattractant
Vmean = 1.8 ± 0.8 µm/s Vmean = 3.3 ± 1.3 µm/s
D. Kim et al. Biomedical Microdevices 14(6), 1009 (2012)
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Active Steering Control using Remote Magnetic Fields
R. W. Carlsen, M. R. Edwards, J. Zhuang, C. Pacoret, & M. Sitti, Lab Chip 14(19), 3850 (2014)
© Metin Sitti, MPI/CMU
Bacteria Propelled Swimming Micro-Robotic Swarms for Future Medical Applications?
Bacteria
Physical platform •! Environment sensing
•! Bacterial actuation
•!Chemotactic/magnetotactic control
Statistical physics computational model
•!Emergence and dynamics of dense networks of bacteria propelled micro-robotic swarms
•!Characterization of collective and competitive behavior
Targeted region
Micro-robotic swarm
Single micro-robot within a swarm
Dense networks of micro-robotic swarms
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Off-Board Approach: External Actuation
Electrostatics Donald et al.,
Dartmouth College, USA (2005)
Scratch-drive
Nelson et al. (2009) Fischer, et al. (2009)!ETHZ Bacterial propulsion
Magnetics
Thermal Sul et al., U. North
Carolina, USA (2006)
Laser excitation 20 µm
100 µm
Yamakazi et al., Tohoku University, Japan (2001)3) Rotational swimmer
Nelson et al., ETHZ (2007) Inertial resonant drive
© Metin Sitti, MPI/CMU
Why Magnetics?
• Versatile and Robust – No specialized surfaces
(vs. Electrostatic) – Long range – No specialized environments
(vs. dirt & humidity) – No line of sight (vs. Optical)
• Favorable to micron scale – High (forces &) torques
Abbott et al., IEEE RAM 14 (2007)
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© Metin Sitti, MPI/CMU Proposed Micro-Robot Motion Principle:
Rotational Stick-Slip Motion • Robot body
– Permanent magnet – Arbitrary geometry
• Pulsed magnetic fields – Torque-based asymmetric
rocking inducing stick-slip – Less than 1 mT sufficient
• Works on complex surfaces • Operates in liquid/air/vacuum
– < 60 mm/s in air – < 40 mm/s in water
C. Pawashe, S. Floyd, and M. Sitti, I. J. Robotics Research 28(8), 1077 (2009)
Mag-µBot
Horizontal coil (x)
Bottom coil (z)
z
x
© Metin Sitti, MPI/CMU
Experimental Setup
Permanent magnet micro-robot
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© Metin Sitti, MPI/CMU
Modeling Mag-µBot Behavior in 2-D • Forces
– Ty: Magnetic torques (1s of µN) – Dy: Damping torque (1s of µN) – Ff: Friction Force (100s of nN) – N: Normal Force (100s of nN) – Fadh: Adhesion (100s of nN) – mg: Weight (100s of nN) – Fx, Fz: Magnetic forces (10s of nN) – Lx, Lz: Damping force (1s of nN)
• Objective – Create a dynamic simulation – Predict robot behavior – Predict robot velocity
Side-‐View Free Body Diagram
Painlevé Paradox (1895)
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Contact Manipulation in Liquids
4 mm 350 µm micro-robot
underwater, 1x realtime
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Autonomous Two-Particle Assembly
C. Pawashe, E. Diller, S. Floyd, and M. Sitti, IEEE Trans. on Robotics 28(2), 467 (2012)
u Vision-based control
u Iterative learning of the pushing distance
• Star-bot on glass in
silicone oil (20 cSt) • 210 µm polymer
sphere • 7.5 µm error tolerance • 2x video speed
© Metin Sitti, MPI/CMU
Fabrication and micro-robotic manipulation of cell-encapsulating hydrogels
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Cell Laden Micro-Gel Assembly 1 mm
1 mm
(a) (b) (c) (d)
(e) (f) (g) (h)
(i) (j)
S. Tasoglu, E. Diller, S. Guven, M. Sitti & U. Demirci, Nature Communications 5 (2014)
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Versatility of Micro-robotic Assembly
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Three-Dimensional Micro-robotic Assembly
© Metin Sitti, MPI/CMU
Spatially Coded Constructs for
Tissue Culturing
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3-D Assembly using Untethered Micro-Grippers
E. Diller and M. Sitti, Advanced Functional Materials 24, 4397 (2014)
© Metin Sitti, MPI/CMU
Non-Contact Manipulation
• Fluid boundary layers generated by moving micro-robot – Drag force applied to micro-objects from fluid (Reynolds number < 1)
50 µm polystyrene sphere silicone oil (20 cSt)
C. Pawashe, S. Floyd, and M. Sitti, IEEE Trans. Robotics 25(6), 1332 (2009)
Finite element modeling of fluid flow for a translating star-bot
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Rolling Locomotion and Particle Transport
Z. Ye, E. Diller & M. Sitti, J. Appl. Phys.
112, 064912 (2012)
© Metin Sitti, MPI/CMU
Non-Contact Cell Transport
Z. Ye & M. Sitti, Lab on a Chip, 14(13), 2177 (2014)
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Non-Contact Motile Cell Transport
© Metin Sitti, MPI/CMU
3D Locomotion: Microswimmers
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Rotational Swimmer using Flexible Flagella } Flexible straight tail + Magnetic body à
Rotational propulsion } Simple to fabricate with many flagella
} Body rotation à Passive bending of tails } Multi-flagella à Extra propulsion
M
Ω
Z. Ye, S. Regnier, and M. Sitti, IEEE Trans. on Robotics 30(1), 3 (2014)
© Metin Sitti, MPI/CMU
Flexible Body Undulation based Soft Microswimmer
m(x)
B
B
B
(a)
(b)
(c)
(d)
(e)camera
coils
workspace
x
y
z
E. Diller, J. Zhuang, G. Z. Lum, M. R. Edwards, & M. Sitti, Applied Physics Letters 104, 174101 (2014)
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Multi-Robot Control
© Metin Sitti, MPI/CMU
Micron Scale Multi-Robot Control
• Fundamental problem: How to address each micro-robot locally using global magnetic fields?
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© Metin Sitti, MPI/CMU Addressing Micro-Robot Teams
Remotely using Novel Magnetic Composites
E. Diller, S. Miyashita, M. Sitti, RSC Advances 2(9), 3850 (2012)
Five spinning micro-robots that could control the fluid flow locally
• No specialized surfaces • In any fluid or air • Many magnetic states • Works also in 3-D • Scalable
© Metin Sitti, MPI/CMU
Self-Organizing Magnetic Micro-Modules
S. Miyashita, E. Diller, & M. Sitti, Int. J. Rob. Res. 32(5), 591 (2013)
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© Metin Sitti, MPI/CMU
Summary
• Bio-hybrid (bacteria-propelled) micro-robots – Chemotactic/pH and remote magnetic steering – Many future challenges towards a clinical use, but the smallest micro-
robotic devices so far
• Magnetic micro-robots – Sub-mm devices possible – Current bioengineering applications – Will be exploring their clinical use (< 1 mm access capability?)
• Potential applications – Medical diagnosis, therapy, and local drug delivery – Single cell manipulation and surgery – Desktop micro-manufacturing