Light controlled 3D micromotors powered by bacteria

Abstract

Self-propelled bacteria can be integrated into synthetic micromachines and act as biological propellers. So far, proposed designs suffer from low reproducibility, large noise levels or lack of tunability. Here we demonstrate that fast, reliable and tunable bio-hybrid micromotors can be obtained by the self-assembly of synthetic structures with genetically engineered biological propellers. The synthetic components consist of 3D interconnected structures having a rotating unit that can capture individual bacteria into an array of microchambers so that cells contribute maximally to the applied torque. Bacterial cells are smooth swimmers expressing a light-driven proton pump that allows to optically control their swimming speed. Using a spatial light modulator, we can address individual motors with tunable light intensities allowing the dynamic control of their rotational speeds. Applying a real-time feedback control loop, we can also command a set of micromotors to rotate in unison with a prescribed angular speed.

Magnetotactic bacteria in a droplet self-assemble into a rotary motor

“…When the magnetic field is rapidly reversed, the MTB that are accumulated at the right of the NP and at the left of the SP can suddenly rotate to align along the new magnetic field, without any restriction from the droplet boundary. After this, they cross the droplet roughly along the y-direction, producing a transient convective circulation with positive values of Ω d (corresponding to CW direction) measured just after the magnetic field reversal (see Recently, considerable efforts have been undertaken to harness the microscopic activity of living or synthetic agents like bacteria [21,44], eukaryotic cells [45], Janus colloids [9] or micro-robots [46,47], in order to extract macroscopic work from microscopic mechanical structures. Here, we show a remarkable example of living biological entities self-assembling into a rotary motor actuated by a controlled, external aligning field.…”

Strategies for Optical Trapping in Biological Samples: Aiming at Microrobotic Surgeons

“…Light‐controllable microparticles can either have predefined shapes (e.g., microtools 3D‐printed in commercial negative photoresists such as IP‐L, IP‐G, Femtobond 4B, SCR‐701, NOA63 and SU‐8, or fabricated in SiO 2 through a double liftoff photolithographic process) or they can be based on light‐responsive materials (e.g., light‐sensitive polymers or liquid crystal elastomers …”

“…Light-controllable microparticles can either have predefined shapes (e.g., microtools 3D-printed in commercial negative photoresists such as IP-L, [228] IP-G, [229] Femtobond 4B, [230] SCR-701, [231] NOA63 [232] and SU-8, [233,234] or fabricated in SiO 2 through a double liftoff photolithographic process [235] ) or they can be based on light-responsive materials (e.g., light-sensitive polymers [236] or liquid crystal elastomers. [237] ) Shape-changing microtools based on light-sensitive materials are responsive to light, but not amenable to optical trapping and manipulation, so they will not be further discussed here.…”

Diffusiophoretic design of self-spinning microgears from colloidal microswimmers

“…The design of structures made from microswimmers is however missing 14,15 , highlighting the lack of simple design rules in dissipative self-assembly 25,26 . Templated assembly has been used to tackle this issue and guide assembly, by using boundaries to direct swimmers 27,28 , resulting in rectified motion [27][28][29][30][31] and exploited to actuate asymmetric microgears 32,33 . However, it relies on preliminary microfabrication and show limited flexibility or control on the assembly.…”