Remotely powered self-propelling particles and micropumps based on miniature diodes

Abstract

Microsensors and micromachines that are capable of self-propulsion through fluids could revolutionize many aspects of technology. Few principles to propel such devices and supply them with energy are known. Here, we show that various types of miniature semiconductor diodes floating in water act as self-propelling particles when powered by an external alternating electric field. The millimetre-sized diodes rectify the voltage induced between their electrodes. The resulting particle-localized electro-osmotic flow propels them in the direction of either the cathode or the anode, depending on their surface charge. These rudimentary self-propelling devices can emit light or respond to light and could be controlled by internal logic. Diodes embedded in the walls of microfluidic channels provide locally distributed pumping or mixing functions powered by a global external field. The combined application of a.c. and d.c. fields in such devices allows decoupling of the velocity of the particles and the liquid and could be used for on-chip separations.

Controlled surface-induced flows from the motion of self-assembled colloidal walkers

“…4A (solid blue curve). Notice the excellent agreement between the simulation and analytical equation that are essentially indistinguishable above z ¼ h. One can see from both of these curves that there is considerable fluid flow in the direction of chain motion, and that it closely resembles a plug flow profile above the rotors, similar to the case of electroosmosis (14,15,26). Also, notice that the value of the maximum velocity is ρ s ∼ νh 3 ∼ ρ s νðaNÞ 3 , implying that the flow can be strongly affected by changing the effective (or average) length of the chains, and thus can be modified by simply changing the strength of the magnetic field.…”

“…For example, scientists have been successful at creating a "forest" of magnetic rods that pulsate in a similar fashion as cilia when driven by using magnetic fields (13), diodes that rely on induced elecroosmosis to move nearby fluid (14,15), and even carpets of fixed bacteria that exploit the machinery already present in biology to create complex flows (16).…”

Design of a UV-responsive microactuator on a smart device for light-induced ON-OFF-ON motion

“…2,6 To address the power supply issue, two strategies have been developed. One is to apply an external field as the driving force, 7,8 which is limited by the specific properties of the materials and is strongly dependent on manual control. The other solution is to introduce an external material flow to provide chemical power, such as the decomposition of hydrogen peroxide 4,[9][10][11][12][13][14][15][16][17][18][19] or the reduction of protons by zinc 20,21 for bubble propulsion or other propelling mechanisms, the Marangoni effect caused by a surface tension gradient [22][23][24] or biomotors such as myosins, kinesins and dyneins via the hydrolysis of adenosine triphosphate.…”

On the self-propulsion of an -sphere micro-robot

“…Studies of micro-robots represent a flourishing modern research topic that strives to create a fundamental base for modern applications in medicine and technology, see Purcell (1977), Becker, Koelher & Ryder (2003), Najafi & Golestanian (2004), Dreyfus et al (2005), Chang et al (2007), Earl et al (2007), Alouges, DeSimone & Lefebvre (2008), Golestanian & Ajdari (2008, 2009, Leoni et al (2009), Alexander, Pooley & Yeomans (2009), Gilbert et al (2010) and Lauga (2011). The simplicity of the geometry represents the major advantage in studies of micro-robots (in contrast with the extreme complexity of self-swimming micro-organisms, e.g.…”