Electrokinetic and optical control of bacterial microrobots

Steager, Edward B.; Sakar, Mahmut Selman; Kim, Dal Hyung; Kumar, Vijay; Pappas, George J.; Kim, Min Jun

doi:10.1088/0960-1317/21/3/035001

Cited by 126 publications

(90 citation statements)

References 39 publications

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“…Recently, there has been a growing interest in using autonomous, micro and nano motile entities, ranging from protein motors to motile cells, to shuttle cargo and produce work [21][22][23][24][25][26][27][28][29][30][31][32][33][34]. For example, motile bacteria have been demonstrated to move objects [21][22][23][24][25] and rotate 'gears' [26].…”

Section: Resultsmentioning

confidence: 99%

Terrain following and applications:Caenorhabditis elegansswims along the floor using a bump and undulate strategy

Yuan

Raizen

et al. 2016

J. R. Soc. Interface.

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Nematodes such as Caenorhabditis elegans are heavier than water. When submerged in water, they settle to the bottom surface. Observations reveal that the animals do not lie flat on the bottom surface, but remain substantially suspended above the surface through continuous collisions with the surface, while maintaining their swimming gaits. Consequently, the swimming animals follow the bottom surface topography. When the bottom surface is inclined, the animals swim up or down along the incline. As the magnitude of the gravitational force can be easily estimated, this behaviour provides a convenient means to estimate the animal's propulsive thrust. The animals' tendency to follow the surface topography provides a means to control the swimmers' trajectories and direction of motion, which we demonstrate with a saw tooth-like ratchet that biases the animals to swim in a selected direction. The animals can also serve as surface topography probes since their residence time as a function of position provides information on surface features. Finally, we take advantage of surface following to construct a simple motility-based sorter that can sort animals based on genotype and state of health. IntroductionMotility assays for nematodes, such as Caenorhabditis elegans, often monitor, from above, the motion of animals suspended in aqueous solutions. In most cases, the animals are observed to swim. Caenorhabditis elegans is, however, heavier than water [1] and sediments to the bottom. Although nematodes' sedimentation per se has not been investigated extensively, nematologists have known for a long time that nematodes sediment in a gravitational field and have taken advantage of this phenomenon to isolate animals (i.e. in the Baermann funnel method) [2]. Nematode settling is also used extensively in various assay preparations [3].That gravitational forces play a significant role in nematodes' hydrodynamics is hardly surprising. To demonstrate that gravitational forces impact nematodes' swimming trajectories, we carry out a simple scaling analysis. Fluid mechanicians define the gravity parameter G ¼ ðr a À r l Þ=r l Â ga 2 =nU, representing the ratio of the gravitational body force ðr a À r l Þga 2 L and the viscous force mUaL=a. In the above, r a and r l are, respectively, the density of the animal and the suspending liquid, L is the length of the animal, g is gravitational acceleration, a is the animal's radius, m is the suspending liquid's viscosity, v ¼ m/r l , and U is the animal's velocity. When an adult C. elegans is suspended in water, ðr a À r l Þ=r l 0:07 [1]. Adult C. elegans has a radius a 40 mm and length L 1 mm. The liquid kinematic viscosity n 10 26 m 2 s 21 and the adult animal's velocity U 200 mm s 21. G is of order 1, indicating that gravitational forces are as important as propulsive forces and significantly impact the animal's swimming trajectory.What happens to the animal once it settles to the bottom? One might naively assume that the animal lies flat on the bottom surface. If this were the case, the anima...

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Section: Resultsmentioning

confidence: 99%

Terrain following and applications:Caenorhabditis elegansswims along the floor using a bump and undulate strategy

Yuan

Raizen

et al. 2016

J. R. Soc. Interface.

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“…For this purpose, several researchers have developed new adhesion methods for anisotropically attaching the bacteria on the microstructures considering the directionality [14], which is the main issue of the research in bacteriaattached microrobot. While one can attach the bacteria during the fabrication of the target object [15], the bacteria can be harmed due to the toxic fabrication process and it is recommended to attach the bacteria after the objects are completely assembled. Behkam et al demonstrated S. marcescens flagellated chemotactic bacteria as bio-actuator for the propulsion of polystyrene microbeads by oxygen plasma treatment.…”

Section: Introductionmentioning

confidence: 99%

Laminar flow assisted anisotropic bacteria absorption for chemotaxis delivery of bacteria-attached microparticle

Huh

Son

et al. 2016

Micro and Nano Syst Lett

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The concepts of microrobots has been drawn significant attentions recently since its unprecedented applicability in nanotechnology and biomedical field. Bacteria attached microparticles presented in this work are one of pioneering microrobot technology for self-propulsion or producing kinetic energy from ambient for their motions. Microfluidic device, especially utilizing laminar flow characteristics, were employed for anisotropic attachment of Salmonella typhimurium flagellated chemotactic bacteria to 30 um × 30 um and 50 um × 50 um microparticles that made of biodegradable polymer. Any toxic chemicals or harmful treatments were excluded during the attachment process and it finished within 100 s for the anisotropic attachment. The attachments were directly confirmed by fluorescent intensity changes and SEM visualization. Chemotaxis motions were tracked using aspartate and the maximum velocity of the bacteria-attached microrobot was measured to be ~5 um/s which is comparable to prior state of art technologies. This reusable and scalable method could play a key role in chemotaxis delivery of functional microparticles such as drug delivery system.

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“…The motive forces in bacteria-based actuators can be generated by several variations of stimuli-induced movements (or taxes), including aerotaxis (taxis to oxygen), chemotaxis (taxis to a carbon source), magnetotaxis (taxis to magnetic field), and phototaxis (taxis to light) [16][17][18]. In particular, magneto-aerotatic bacteria have a potential for targeting the cancer cells due to the controllable movements with an external magnetic field [19].…”

Section: Introductionmentioning

confidence: 99%

Motility Control of Bacteria-Actuated Biodegradable Polymeric Microstructures by Selective Adhesion Methods

2014

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Certain bacteria have motility and can be made non-toxic, and using them for drug delivery has been proposed. For example, using bacteria with flagella motion in multiple spin actuators in drug delivery microrobots has been suggested. This paper investigates various adhesion enhancement methods for attaching bacteria on preferred surfaces of cubic polymeric microstructures to achieve the directional control of motion. Serratia marcescens which has an excellent swimming behavior and 50-μm sized cubic structures made of biodegradable poly-capro-lactone (PCL) are used. Three treatment methods are investigated and compared to the untreated control case. The first method is retarding bacterial attachments by coating certain surfaces with bovine serum albumin (BSA) which makes those surfaces anti-adherent to bacteria. The second and third methods are roughening the surfaces with X-ray irradiation and plasma respectively to purposely increase bacterial attachments on the roughened surfaces. The measured motilities of bacteria-tethered PCL microactuators are 1.40 μm/s for the BSA coating method, 0.82 μm/s for the X-ray irradiation, and 3.89 μm/s for the plasma treatment method. Therefore, among the methods investigated in the paper the plasma treatment method achieves the highest directionality control of bacteria motility. OPEN ACCESSMicromachines 2014, 5 1288

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Electrokinetic and optical control of bacterial microrobots

Cited by 126 publications

References 39 publications

Terrain following and applications:Caenorhabditis elegansswims along the floor using a bump and undulate strategy

Terrain following and applications:Caenorhabditis elegansswims along the floor using a bump and undulate strategy

Laminar flow assisted anisotropic bacteria absorption for chemotaxis delivery of bacteria-attached microparticle

Motility Control of Bacteria-Actuated Biodegradable Polymeric Microstructures by Selective Adhesion Methods

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