Unraveling the Autonomous Motion of Polymer‐Based Catalytic Micromotors Under Chemical−Acoustic Hybrid Power

Abstract

Artificial nano‐ and microswimmers are promising as versatile nanorobots for applications in biomedicine, environmental chemistry, and materials science. Herein, a hybrid micromotor containing a conjugated polymer (poly(3,4‐ethylenedioxythiophene) (PEDOT), and a catalytic structure composed of platinum (Pt) synthesized using a template‐supported electrochemical deposition process is reported. The movement of this PEDOT/Pt micromotor is characterized under chemical power generated by hydrogen peroxide catalysis, and acoustic power generated by surface acoustic waves (SAWs). The acoustic radiation force acting between the bubbles, the secondary Bjerknes force, is shown to increase the micromotor speed. The movement of the micromotor is precisely controllable using the acoustic field, providing excellent response time and reproducibility over a wide dynamic range. A theoretical model is developed to understand and predict the micromotor propulsion under the hybrid chemical and acoustic power. Predicted micromotor speeds are in excellent agreement with experiment as a function of peroxide fuel concentration, SAW field strength, and SAW frequency. The model allows for design of micromotor geometries and acoustic field strengths to achieve desired speed with excellent on/off control.

Fluorescence Detection of miRNA-21 Using Au/Pt Bimetallic Tubular Micromotors Driven by Chemical and Surface Acoustic Wave Forces

“…The fabrication process of Au/Pt microtubes is shown in Scheme . Au/Pt micromotors were synthesized following the template electrodeposition process as described previously . A polycarbonate (PC) membrane, which contains cylindrical nanopores with a diameter of 200 nm, was used as a template (catalog no.…”

“…The acoustofluidic device consists of a SAW generator manufactured with a square glass capillary from a 128° rotated Y -cut X -propagation lithium niobate (LiNbO 3 ) substrate containing interdigital transducers (IDs) placed on it. The SAW devices were fabricated following the standard photolithography method reported previously . IDTs involving 60 pairs of electrodes were patterned on the substrate with a finger width of 10 μm and a delay path of an 8 mm length and a 2 mm width.…”

“…In the presence of standing SAW, secondary Bjerknes force acts on the bubble and causes an increase in the micromotor speed . The time-averaged secondary Bjerknes force acting on the bubble over one oscillation cycle (1/ f SAW ) is given by where f SAW , ρ, ε, and d 12 are the applied SAW frequency, solution density, displacement amplitude, and inter-bubble distance, respectively.…”

“…Artificial micro- and nanomotors have fascinating capability to move autonomously or under different external energy sources. These molecular machines play an important role in the development of medical applications including active drug delivery, fast detection of tumor markers, and payload transport into cells. − In comparison to conventional nanocarriers, the nano/micromotors offer several advantages for cell internalization, including enhanced adhesion, better penetration, and a shorter and controllable transporting time based on the propelling mechanism. − Early studies in the synthesis and application of nano/micromotors focused only on designs based on micromotor motions powered by magnetic, ultrasound, − and chemical propulsion mechanisms , and their combinations. , Chemical propulsion is fast motion, but fuels can have a toxic effect, which limits biological applications. Unlike chemical propulsion, acoustic propulsion especially offers a unique opportunity to use such microscale devices in biological applications because of its non-toxic fuel requirement, tunability, and prolonged operation time .…”

Reversible morphology-resolved chemotactic actuation and motion of Janus emulsion droplets

“…Utilizing these dynamics, a series of artificial soft-matter robots on the micro- or nanoscale powered by chemical fuels have been reported. Motion can be mediated by (photo-)catalytic reactions at their interface 11 , 12 , surface-encoded translation pathways 13 , by bacteria 14 , or via different physical stimuli, including light, sound, magnetic, or electric fields 15 – 19 .…”