On‐Demand Coalescence and Splitting of Liquid Marbles and Their Bioapplications

Abstract

Coalescence and splitting of liquid marbles (LMs) are critical for the mixture of precise amount precursors and removal of the wastes in the microliter range. Here, the coalescence and splitting of LMs are realized by a simple gravity‐driven impact method and the two processes are systematically investigated to obtain the optimal parameters. The formation, coalescence, and splitting of LMs can be realized on‐demand with a designed channel box. By selecting the functional channels on the device, gravity‐based fusion and splitting of LMs are performed to mix medium/drugs and remove spent culture medium in a precise manner, thus ensuring that the microenvironment of the cells is maintained under optimal conditions. The LM‐based 3D stem cell spheroids are demonstrated to possess an approximately threefold of cell viability compared with the conventional spheroid obtained from nonadhesive plates. Delivery of the cell spheroid to a hydrophilic surface results in the in situ respreading of cells and gradual formation of typical 2D cell morphology, which offers the possibility for such spheroid‐based stem cell delivery in regenerative medicine.

Liquid Metal–Based Soft Microfluidics

“…LM macrosized droplets, similar to water droplets, tend to achieve a spherical shape in air due to the tendency to minimize the surface energy. The wetting and dewetting of LM can be tuned by the adjustment of the surface energy and surface roughness of the wetted substrate . However, distinguished from a water droplet, the LM shows some unique features in both bulk and at its surface.…”

“…The wetting and dewetting of LM can be tuned by the adjustment of the surface energy and surface roughness of the wetted substrate. [47,[97][98][99] However, distinguished from a water droplet, the LM shows some unique features in both bulk and at its surface. The bulk material is made of metal, which imparts the LM excellent conductivity.…”

Bubble-Assisted Three-Dimensional Ensemble of Nanomotors for Improved Catalytic Performance

“…The generated bubbles, on the one hand, lowered the average volume density of the dynamic pattern. On the other hand, the generated bubble among the B-MCS ensembles dewet the particles surface to form the Cassie-Baxter wetting state (Wang et al., 2015, Wang et al., 2019a, Wang et al., 2019b, Lee and Kim, 2011, Cassie and Baxter, 1994, Jin et al., 2018) by converting the solid-liquid-solid interface into the solid-gas-solid interface and thus largely reduced the friction force between the nanocatalysts and the substrate. Likewise, on the other directions, the interface between the nanocatalysts and the solution was altered from the solid-liquid interface to solid-air-liquid interface, which also contributed to the spatial drag reduction.…”

Liquid Marbles in Liquid

“…Liquid marbles (LMs) are liquid droplets encapsulated by hydrophobic particles at the liquid–gas interface; this phenomena has recently drawn increasing interest due to their superior mobility, [ 1–4 ] elasticity, [ 5 ] and stability. [ 6,7 ] These beneficial characteristics have allowed LMs to be successfully applied as microreactors, [ 8–11 ] in microfluidic control, [ 12–15 ] gas sensing, and many other engineering areas. [ 16–19 ] Compared with the uncoated “naked” droplets, LMs can be manipulated as non‐sticky fluidic cells with significantly reduced surface friction and increased drop operability.…”

“…In addition, LMs with shells composed of multilayers of particles can be engineered for precise control of chemical dosing by allowing them to coalesce and disintegrate at specific interval. [ 7,33 ] The combination of simple manipulation, accurate control, and overarching benefits of microreactors give LMs promising advantages in both chemical analysis and biomedical applications.…”