Manipulation
of gas bubbles in an aqueous ambient environment is
fundamental to both academic research and industrial settings. Present
bubble manipulation strategies mainly rely on buoyancy or Laplace
gradient forces arising from the sophisticated terrain of substrates.
However, these strategies suffer from limited manipulation flexibility
such as slow horizontal motion and unidirectional transport. In this
paper, a high performance manipulation strategy for gas bubbles is
proposed by utilizing ferrofluid-infused laser-ablated microstructured
surfaces (FLAMS). A typical gas bubble (<2 μL) can be accelerated
at >150 mm/s2 and reach an ultrafast velocity over 25
mm/s
on horizontal FLAMS. In addition, diverse powerful manipulation capabilities
are demonstrated including antibuoyancy motion, “freestyle
writing”, bubble programmable coalescence, three-dimensional
(3-D) controllable motion and high towing capacity of steering macroscopic
object (>500 own mass) on the air–water interface. This
strategy
shows terrain compatibility, programmable design, and fast response,
which will find potential applications in water treatment, electrochemistry,
and so on.
Droplet
manipulation is crucial for diverse applications ranging
from bioassay to medical diagnosis. Current magnetic-field-driven
manipulation strategies are mainly based on fixed or partially tunable
structures, which limits their flexibility and versatility. Here,
a reconfigurable magnetic liquid metal robot (MLMR) is proposed to
address these challenges. Diverse droplet manipulation behaviors including
steady transport, oscillatory transport, and release can be achieved
by the MLMR, and their underlying physical mechanisms are revealed.
Moreover, benefiting from the magnetic-field-induced active deformability
and temperature-induced phase transition characteristics, its droplet-loading
capacity and shape-locking/unlocking switching can be flexibly adjusted.
Because of the fluidity-based adaptive deformability, MLMR can manipulate
droplets in challenging confined environments. Significantly, MLMR
can accomplish cooperative manipulation of multiple droplets efficiently
through on-demand self-splitting and merging. The high-performance
droplet manipulation using the reconfigurable and multifunctional
MLMR unfolds new potential in microfluidics, biochemistry, and other
interdisciplinary fields.
Superhydrophobic/superhydrophilic surfaces (SBS/SLS) with excellent water repellency/adhesion are important in both academic research and industrial settings owing to their intriguing functions in tiny droplet and gas bubble manipulation. However, most manipulation strategies involving SBS/SLS are limited to their large-area fabrication or sophisticated morphology designs, which distinctly hinders their practical uses. In this paper, we design and fabricate superhydrophobic polydimethylsiloxane narrowing dual rails (SNDRs) beneath a superhydrophilic stainless steel sheet by one-step femtosecond laser ablation. Our SNDR tracks are capable of transporting gas bubbles in various volumes from wide end to narrow end spontaneously and unidirectionally underwater, even when they are bent. The mechanical analysis for diverse geometrical dual-rail configurations in bubble transportation performance is further discussed. Finally, we experimentally demonstrate the intriguing capability of lossless mixing of gas bubbles at a designed volume ratio on a multiple SNDR combination. This approach is facile and flexible, and will find broad potential applications such as intelligent bubble transport, mixing, and controllable chemical reactions in interfacial science and microfluidics.
High‐performance droplet transport is crucial for diverse applications including biomedical detection, chemical micro‐reaction, and droplet microfluidics. Despite extensive progress, traditional passive and active strategies are restricted to limited liquid types, small droplet volume ranges, and poor biocompatibilities. Moreover, more challenges occur for biological fluids due to large viscosity and low surface tension. Here, a vibration‐actuated omni‐droplets rectifier (VAODR) consisting of slippery ratchet arrays fabricated by femtosecond laser and vibration platforms is reported. Through the relative competition between the asymmetric adhesive resistance originating from the lubricant meniscus on the VAODR and the periodic inertial driving force originating from isotropic vibration, the fast (up to ≈60 mm s−1), programmable, and robust transport of droplets is achieved for a large volume range (0.05–2000 µL, Vmax/Vmin ≈ 40 000) and in various transport modes including transport of liquid slugs in tubes, programmable and sequential transport, and bidirectional transport. This VAODR is general to a high diversity of biological and medical fluids, and thus can be used for biomedical detection including ABO blood‐group tests and anticancer drugs screening. These strategies provide a complementary and promising platform for maneuvering omni‐droplets that are fundamental to biomedical applications and other high‐throughput omni‐droplet operation fields.
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