Investigating environmental processes,
especially those occurring
in soils, calls for innovative and multidisciplinary technologies
that can provide insights at the microscale. The heterogeneity, opacity,
and dynamics make the soil a “black box” where interactions
and processes are elusive. Recently, microfluidics has emerged as
a powerful research platform and experimental tool which can create
artificial soil micromodels, enabling exploring soil processes on
a chip. Micro/nanofabricated microfluidic devices can mimic some of
the key features of soil with highly controlled physical and chemical
microenvironments at the scale of pores, aggregates, and microbes.
The combination of various techniques makes microfluidics an integrated
approach for observation, reaction, analysis, and characterization.
In this review, we systematically summarize the emerging applications
of microfluidic soil platforms, from investigating soil interfacial
processes and soil microbial processes to soil analysis and high-throughput
screening. We highlight how innovative microfluidic devices are used
to provide new insights into soil processes, mechanisms, and effects
at the microscale, which contribute to an integrated interrogation
of the soil systems across different scales. Critical discussions
of the practical limitations of microfluidic soil platforms and perspectives
of future research directions are summarized. We envisage that microfluidics
will represent the technological advances toward microscopic, controllable,
and in situ soil research.
Joule heating is featured with an extremely high rising rate of temperature with hundreds of kelvin per second, which has shown superiorities of high efficiency and energy conservation in graphene fabrication. Herein, we design a dynamic joule heating system for continuous synthesis of graphene fibers with ultrashort high‐temperature (≈2000 °C), treating time (≈20 min), and low electric energy consumption (≈2000 kJ m−1). During the joule heating fabrication, the current flowing through the fibers can manipulate the configuration of graphene sheets, the basic component units of fiber, and induce their alignment. Theoretical simulations reveal that graphene sheets tend to rotate towards the current direction under the current induced electric field for the highest stability with the lowest electric free energy and zero rotation torque. Therefore, the electrical and mechanical performances of as‐fabricated graphene fibers can be further improved in comparison with thermally annealed graphene fibers without applying current.
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