Photo- and Thermoresponsive Liquid Marbles Based on Fatty Acid as Phase Change Material Coated by Polypyrrole: From Design to Applications

Abstract

Responsive liquid marbles (LMs), which can change their shape, stability, and motion by the application of stimuli, attract a growing interest due to their wide range of applications. Our approach to design photo- and thermoresponsive LMs is based on the use of micrometer-sized fatty acid (FA) particles as phase change material covered with polypyrrole (PPy) overlayers with photothermal property. The core–shell particles were synthesized by aqueous chemical oxidative seeded dispersion polymerization. First, we investigated the effect of the alkyl chain length of FA on the resulting FA/PPy core–shell particles by characterizing their size and its distribution, shape, morphology, chemical composition, and photothermal behavior. Then LMs were fabricated by rolling water droplets on the dried FA/PPy particle powder bed and their light and temperature dual stimuli-responsive nature was studied as a function of the FA alkyl chain length. For all FAs studied, LMs disrupted in a domino manner by light irradiation as the first trigger: the temperature of the FA/PPy particles on the LM surface increased by light irradiation, followed by phase change of FA core of the particles from solid to liquid, resulting in disruption of the LM and release of the encapsulated water. The disruption time was closely correlated to the melting point of FA linked to the alkyl chain length and light irradiation power, and it could be controlled and tuned easily between quasi instantaneous and approximately 10 s. Finally, we showed potential applications of the LMs as a carrier for controlled delivery and release of substances and a sensor.

pH-Responsive Liquid Marbles Stabilized with Chitosan-Stearic Acid-Conjugated Particles

“…This was not particularly surprising, considering that only the surfaces of the CS particles were modified by SA and the SA loading amounts were too low to be detected in the FT-IR studies. 64,65 Elemental microanalyses offered information about the extent of SA modification. The modification degree was determined from the C/N mass ratio (Table 1) because the SA component increased the mass of carbon compared with nitrogen.…”

“…Due to the ease of chemical modifications with the amino groups in CS, various derivatives have been synthesized − for a range of applications, such as bioreactors, photonic materials, photocatalysts, flocculants, antimicrobials, − emulsifiers, nematode control, food packing, and drug delivery carriers . SA is a natural fatty acid widely used as a biocompatible and biodegradable hydrophobizer for solid substrates. − Due to its versatility, abundance, and low cost, SA is a particularly attractive material among fatty acids . In this study, we first synthesized CS-SA-conjugated particles by direct solvent-free thermal amidation between CS and SA.…”

Nonspherical Epoxy Resin Polymer Particles Synthesized via Solvent-Free Polyaddition Reactions

“…Liquid droplets stabilized in air by adsorption of hydrophobic solid particles on the droplet surface are called liquid marbles (LMs). − Since the LMs are covered by solid particles, the liquid can be treated as a soft solid. Recently, LMs have attracted increasing interest because of their potential for use as miniature reactors, ,− sensors, − microcentrifuges, microfluidics, collision-based computing devices, and material carriers. − Various solid particles, including lycopodium, silica particles, polytetrafluoroethylene (PTFE) particles, and polystyrene particles, have been used as stabilizers for LMs. Most of the stabilizers are spherical or have ill-defined shapes, and their ill-defined aggregates are often adsorbed on the droplet surfaces as LM stabilizers.…”

Universality of Scaling Laws Governing Contact and Spreading Time Spans of Bouncing Liquid Marbles and its Physical Origin

“…Our work is devoted to the study of the bouncing of liquid marbles, first introduced in the pioneering paper by Quéré et al. − Liquid marbles (LMs) are droplets coated with colloidal particles enabling separation of the liquid within from the solid substrate by an air layer. − This separation gives rise to the high mobility of liquid marbles, thus representing an alternative to the lotus-like-inspired superhydrophobicity . Properties and applications of liquid marbles were studied intensively in the last decade. − Several biological applications of liquid marbles were reported. , In particular, the use of liquid marbles as microfluidic devices and micromixers was demonstrated. , Various techniques enabling fabrication of liquid marbles including noncontact and electrostatic manufacturing were described. , It should be mentioned that liquid marbles are separated from the solid substrate with air cushions, thus resembling the wetting regime inherent for superhydrophobic surfaces. − , Our present paper is focused on universal laws describing bouncing liquid marbles on solid substrates.…”