An Electrostatic Method for Manufacturing Liquid Marbles and Particle-Stabilized Aggregates

Abstract

We have developed a method for transferring particles from a powder bed to a liquid droplet using an electric field. This process has been used to create liquid marbles with characteristics not normally found in those formed by direct contact methods such as rolling. It has also been used to manufacture hydrophilic particle-liquid aggregates and more complex layered aggregates incorporating both hydrophobic and hydrophilic particles. This article briefly outlines the electrostatic aggregation method itself, the materials used and structures formed thus far, and explores the rich fundamental physics and chemistry underpinning the process as they are understood at present.

Formation of liquid marbles & aggregates: rolling and electrostatic formation using conductive hexagonal plates

“…Furthermore, it allows for the use of hydrophilic particles to form particle-stabilised aggregates, where the particles are internalised in the droplet resulting in a metastable structure. 25,26 Liquid marbles formed using this method are still able to retain all the applications and characteristics of traditional liquid marbles, whilst allowing for the possibility of scalability and formation of complex structures involving the internalisation of hydrophilic particles before encapsulation takes place with hydrophobic particles. 25,27 However, some of the limitations of this particular method are that the particles must overcome interparticle forces, such as cohesion and friction in order to be extracted to the pendent droplet, which may be aided by increased conductivity and particle size.…”

“…25,26 Liquid marbles formed using this method are still able to retain all the applications and characteristics of traditional liquid marbles, whilst allowing for the possibility of scalability and formation of complex structures involving the internalisation of hydrophilic particles before encapsulation takes place with hydrophobic particles. 25,27 However, some of the limitations of this particular method are that the particles must overcome interparticle forces, such as cohesion and friction in order to be extracted to the pendent droplet, which may be aided by increased conductivity and particle size. 22,23,28 To this end, the viability of relatively large conductive platelets, compared to those previously studied, 22,23,28 to stabilise a droplet will be investigated.…”

“…21,34 These newly synthesised coatings will be investigated with respect to their viability as liquid marble stabilisers using both the traditional rolling 1,4,21 and the contactless electrostatic method of liquid marble formation, during which their electrostatic transfer behaviour will be investigated. 22,23,25,28,35…”

Long‐Lived Liquid Marbles for Green Applications

“…[50] The occurrence of these hydrophilic aggregates within the formation of an LM has been reported in studies where electrostatic formation was employed, explaining how aggregates could be used to form LMs. [51,52] However, for individual hydrophilic particles, it is thermodynamically unfavorable for the particles to coat the droplets exterior, yet once a certain point of wetting is reached any increase would be energetically more expensive and thus remains in a metastable state. [53] Hydrophilic LMs are most commonly formed from either graphite, [17,54] or carbon black, [50,55] and fabricated in the same way as their hydrophobic counterparts.…”

Belousov–Zhabotinsky reaction in liquid marbles

“…This avoids surface contamination problems and allows fast displacement and easy manoeuvrability of the droplets. To prepare LMs, droplets of liquid are encapsulated in a powder coating by rolling the droplets on a powder bed or via an electrostatic method [74,75]. The powder coatings are typically hydrophobic powders such as polyethylene (PE) or polytetrafluoroethylene (PTFE), however hydrophilic powders have also been reported e.g.…”