Controlled Microassembly and Transport of Nano- and Micro-components using Bacteria. Sylvain Martel

Transcription

1 Controlled Microassembly and Transport of Nano- and Micro-components using Bacteria Sylvain Martel NanoRobotics Laboratory Department of Computer and Software Engineering, and Institute of Biomedical Engineering École Polytechnique de Montréal (EPM) Montréal, Canada 1

2 Induced force versus selfpropelled microcarriers or microrobots (+ sensors) to manipulate and transport components

3 Self-assembled and self-reproducing computer-controlled biological bacterial microrobots vs. an hypothetical artificial microrobot Steering system (chain of magnetic nanoparticles) Weapons (encapsulated drug molecules Fuel line (proton flux) Collectors (nutrients or fuel intake from environment) Propulsion (flagella) providing a velocity between 100 and 150 body lengths per second Chemical to mechanical energy converter (near 100% efficiency) Various sensors (oxygen, chemical, light, etc ) ATPase molecular motors (design similar to modern engineered rotary motors with stator and rotor providing between 4.0 and 4.7 piconewtons of thrust)

4 SPECIFICATIONS MC-1 Magnetotactic Bacteria (MTB) - Specifications Diameter of the cell: 1 to 2 micrometers; Thrust propulsive force: 4.0 to 4.7 piconewtons (pn); Velocity: 200 to 300 micrometers per second; Chain of magnetic nanoparticles in the cell acting like a steering system that can be controlled by an external computer by inducing a directional torque from a weak (slightly higher than geomagnetic field) magnetic field. Integrated sensors (taxis) Self-replicating; Self-assembly for attaching nanocomponents

5 Propulsion Directional (Steering) Control The Magnetotactic Bacterium (MTB) 5

6 Steering System

7 Borrowing From Nature Nanorobotics Laboratory, EPM

8 The molecular motor embedded in flagellated bacteria measures less than 300 hydrogen atoms across. This rotary engine composed of proteins is powered by a flow of protons which makes it particularly attractive in implementations where the availability of electrical power is very limited or constrained. The shape of the bacterial flagellum acting like a propeller consists of a 20 nanometer (nm) -thick hollow tube. It has a helical shape with a sharp bend outside and next to the outer membrane. Put together, they form what looks like a hook where a shaft runs between the hook and the basal body. The shaft then passes through protein rings in the cell's membrane that act as bearings. Counter-clockwise rotations of a polar flagellum thrust the cell forward. Propulsion

9 Steering Directional Control The magnetite chain in magnetotactic bacteria acting like a compass needle can be rotated by a magnetic field because of the torque exerted on their magnetite particles. In other words, this chain of magnetosomes imparts to the MTB a magnetic moment that generates sufficient torque so that the bacteria can align themselves to magnetic field lines. This is referred to as magnetotaxis.

10 Directional Control Methods Taxis-based (Positive (toward) nor negative (away) Magnetotaxis Aerotaxis Chemotaxis Phototaxis Etc. Structural-based

11 Taxis-based Source of taxis (e.g. magnetotaxis) generated by an external controller Source of taxis (e.g. magnetotaxis) to indicate the direction of the target Bacterium Planned trajectory Trajectory Deterministic Assisted (semi-autonomous) Obstacles Target Trajectory (less deterministic) Environmental Source of attractant Embedded program: consumable source of attractant (e.g. oxygen) Programmed trajectory Hybrid bacterial microrobot Autonomous Trajectory Influenced by taxis 2 Influenced by taxis 1 Switched (time-multiplexed) multi-taxes Trajectory Simultaneous multi-taxes Influenced by taxis 1 and taxis 2

12 In blood 12

13 NanoRobotics Laboratory TRACKING a TE = 96 ms TE = 125 ms TE = 135 ms

14 14

15 Structural-based 4 capillary channels, one in each corner of a square channel 1 2 Channel Weak field Strong field Channel Strong field Fiber Swimming direction Capillary channels Magnetotactic bacteria

16 Structural-based An asymmetric structure can result in a spontaneous and unidirectional motion or rotation of fabricated objects immersed in an active bacterial bath; by integrating magnetic fields of various intensities within fluidic microstructures and constraining the swimming paths of the bacteria with thin fluidic layers (incl. around wires), directional controlled micro-transport systems requiring no electrical power can be implemented; magnetic field and structural geometries have been exploited to change the directional preferences of MTB and hence, increasing the level of directional control; restricted geometries and solid planar surfaces can also be exploited to influence the motion behavior of flagellated bacteria; the implementation of a solid surface can be used to force the bacteria to swim in circles, etc.

17 Swimming velocity and stop/resume control methods ph level can regulate genes for flagellar motility and as such, control can be done by modifying the property of the liquid medium; phototactic stop/resume is also possible; temperature influence motility; increase in the pitch angle of the MTB helical motion at higher magnetic fields; Other environmental approaches are also possible such as the addition of oxygen and arginine that can also play a role on bacterial motility; Structural approaches such as the proximity of a solid-liquid interface; modification or an exploitation of the viscosity of the environmental liquid medium; Porosity of the surface, etc. The knowledge about the causes of the variations in swimming velocity of bacteria to use them to implement novel motile biosensors or measurement/characterization devices.

18 Transporting objects of approx. 100 microns

19 SWARM - AGGREGATION Scaling force Dosage

20 Prototype platform with the generated 3D magnetic fields

21 A Swarm of 3000 flagellated bacteria B Swarm of 3000 flagellated bacteria pushing microrobot B towards microrobot A Direction of motion Microrobot A Microrobot B C D The swarm finally places the V- shaped microrobot B next to the V- shaped microrobot A to form a structure resembling the character M as in Microrobot. Microrobot B being rotated and pushed by the swarm towards microrobot A REF: Martel et al. ICRA 2009

22 Transporting objects of a few microns

23 Go straight for 2.5 sec.; 2. Then turn left 30 o ; 3. Continue for 1.5 sec.; 4. Then stop. 1 Ref.: Martel S., Tremblay C., Ngakeng S., and Langlois G., Controlled manipulation and actuation of micro-objects with magnetotactic bacteria, Applied Physics Letters, vol. 89, pp , 2006

24 Transporting nano-objects

25 Loading the bacteria with drug encapsulated in liposomes Field-emission scanning electron microscopy images of (left) architecture of unloaded MC-1 MTB and (right) the same strain with liposomes (170 nanometers (nm))

26 Bacteria microassembly and transport in microsystems

27 Transport, mixing, etc. Left - CMOS integrated circuit interacting with MC-1 cells as actuators for controlled manipulation tasks; Right CMOS integrated circuit for the fast detection of pathogens using magnetotactic bacteria as controlled displacement sensors