Yizhen Liu

Liquid metal sponges for mechanically durable, all-soft, electrical conductors

Liquid metal sponges were developed by loading liquid metals (GaInSn) into elastomer sponges. The elasticity of 3D-interconnected networks and the fluidic nature of liquid metals led to the formation of all-soft structures for electrical conductors with high electrical conductivity and mechanical flexibility.

Liquid metal droplets with high elasticity, mobility and mechanical robustness

Non-stick, ultra-elastic liquid metal droplets were fabricated by coating polytetrafluoroethylene (PTFE) particles onto the surface of NaOH-treated liquid metal droplets. The liquid metal droplets consisted of a liquid metal core, a thin anti-oxidation layer to maintain the high surface tension of the liquid metal and a particle-interpenetrated shell to enhance the mobility of the droplet.

Hydrophilic Sponges for Leaf-Inspired Continuous Pumping of Liquids

A bio‐inspired, leaf‐like pumping strategy by mimicking the transpiration process through leaves is developed for autonomous and continuous liquid transport enabled by durable hydrophilic sponges. Without any external power sources, flows are continuously generated ascribed to the combination of capillary wicking and evaporation of water. To validate this method, durable hydrophilic polydimethylsiloxane sponges modified with polyvinyl alcohol via a “dip‐coat‐dry” method have been fabricated, which maintains hydrophilicity more than 2 months. The as‐made sponges are further applied to achieve stable laminar flow patterns, chemical gradients, and “stop‐flow” manipulation of the flow in microfluidic devices. More importantly, the ease‐of‐operation and excellent pumping capacity have also been verified with over 24 hs pumping and quasi‐stable high flow rates up to 15 µL min−1. The present strategy can be easily integrated to other miniaturized systems requiring pressure‐driven flow and should have potential applications, such as cell culture, micromixing, and continuous flow reaction.

Microfluidic Patterning of Metal Structures for Flexible Conductors by In Situ Polymer‐Assisted Electroless Deposition

A low‐cost, solution‐processed, versatile, microfluidic approach is developed for patterning structures of highly conductive metals (e.g., copper, silver, and nickel) on chemically modified flexible polyethylene terephthalate thin films by in situ polymer‐assisted electroless metal deposition. This method has significantly lowered the consumption of catalyst as well as the metal plating solution.

Organic sponge photocatalysis

The successfully developed polydimethylsiloxane (PDMS, a green and highly transparent polymer material) sponge photocatalyst can catalyze cross-dehydrogenative coupling (CDC) of tertiary amines and various nucleophiles with high efficiency and reusability under visible light irradiation. Through an easy-to-build continuous flow reactor, the sponge photocatalytic reaction can be facilely scaled up.

Directed Aromatic C–H Activation/Acetoxylation Catalyzed by Pd Nanoparticles Supported on Graphene Oxide

The first solid-supported directed aromatic C-H activation/acetoxylation has been successfully developed by using palladium nanoparticles supported on graphene oxide (PdNPs/GO) as a catalyst. The practicability of this method is demonstrated by simple preparation of catalyst, high catalytic efficiency, wide functional group tolerance, and easy scale up of the reaction. A hot filtration test and Hg(0) poisoning test indicate the heterogeneous nature of the catalytic active species.

Defect-free, high resolution patterning of liquid metals using reversibly sealed, reusable polydimethylsiloxane microchannels for flexible electronic applications

This paper describes a simple and reliable approach for high-resolution patterning of liquid metals onto elastomeric substrates and their applications in flexible and wearable electronics. In this method, the liquid metal eutectic gallium indium (EGaIn) alloy was first dispensed into an air plasma-treated polydimethylsiloxane (PDMS) substrate through a reversibly sealed PDMS microchannel. The liquid metal-filled substrate was then placed on a cold plate, where the liquid metal was solidified. Finally, defect-free patterns were obtained by directly peeling off the PDMS microchannel on a hot plate while the liquid metal started to melt. The as-made liquid metal patterns exhibited excellent electrical and mechanical performance. As a proof of concept, the as-made flexible patterns of liquid metals were applied as flexible electrical conductors, capacitive sensors, and touch keyboards.

High-absorption recyclable photothermal membranes used in a bionic system for high-efficiency solar desalination via enhanced localized heating

Desalination utilizing solar energy is an effective way to mitigate the crisis of water shortage, but its large-scale application in production has been largely limited by the low evaporation efficiency. Here, we report a plate thermal reduction (PTR) method for rapid preparation of plasmonic-active filter paper (PP) as the photothermal material with broadband solar absorption over 92%. By imitating the spontaneous water circulation mechanism of plants, we designed a high-efficiency bionic solar evaporation and desalination system. Air with excellent low thermal conductivity was used as the thermal insulation material. Because of the enhanced localized heating effect, the system features a high solar evaporation efficiency of up to 89% under 10 kW m−2. Furthermore, under natural sunlight, the bionic system has a drinkable freshwater production rate of 0.97 kg m−2 h−1 under about 0.9 kW m−2 with the highest evaporation efficiency of 79% for one day. With simple material preparation and efficient and stable performance, the bionic system is ideal for large-scale production to tackle energy, water resource and environmental issues.

Bioinspired, Mechano-Regulated Interfaces for Rationally Designed, Dynamically Controlled Collection of Oil Spills from Water

This study describes the fabrication of bioinspired mechano‐regulated interfaces (MRI) for the separation and collection of oil spills from water. The MRI consists of 3D‐interconnected, microporous structures of sponges made of ultrasoft elastomers (Ecoflex). To validate the MRI strategy, ecoflex sponges are first fabricated with a low‐cost sugar‐leaching method. This study then systematically investigates the absorption capacity (up to 1280% for chloroform) of the sponges to different oils and organic solvents. More importantly, the oil flux through the as‐made sponges is controlled by mechanical deformation, which increases up to ≈33‐fold by tensile strain applied to the sponge from 0 to 400%. On the basis of MRI, this study further demonstrates the application of ecoflex sponges in oil skimmers for selective collecting oil from water with high efficiency and durable recyclability. The as‐developed MRI strategy has opened a new path to allow rational design and dynamical control toward developing high performance devices for oil permeation and selective collection of oil spills from water.

Polydimethylsiloxane Sponge‐Supported Nanometer Gold: Highly Efficient Recyclable Catalyst for Cross‐Dehydrogenative Coupling in Water

Polydimethylsiloxane (PDMS, a stable hydrophobic polymer material) sponge-supported nanometer-sized gold can be used as a highly efficient recyclable catalyst for cross-dehydrogenative coupling of tertiary amines with various nucleophiles in water. This PDMS sponge nanometer gold catalyst can provide much better activity than the free nanometer gold in water. The reaction can be scaled up by using an easy-to-build continuous flow reactor. These results indicate the potential application of porous hydrophobic PDMS sponge material as a promising support for highly efficient recyclable catalysts in water.