Micropatterns
of conductive polymers are key for various applications in the fields
of flexible electronics and sensing. A bottom-up method that allows
high-resolution printing without additives is still lacking. Here,
such a method is presented based on microprinting by the laser-induced
microbubble technique (LIMBT). Continuous micropatterning of polyaniline
(PANI) was achieved from a dispersion of the emeraldine base form
of PANI (EB-PANI) in n-methyl-2-pyrrolidone (NMP).
A focused laser beam is absorbed by the EB-PANI nanoparticles and
leads to formation of a microbubble, followed by convection currents,
which rapidly pin EB-PANI nanoparticles to the bubble/substrate interface.
Micro-Raman spectra confirmed that the printed patterns preserve the
molecular structure of EB-PANI. A simple transformation of the printed
lines to the conducting emeraldine salt form of PANI (ES-PANI) was
achieved by doping with various acid solutions. The hypothesized deposition
mechanism was verified, and the resulting structures were characterized
by microscopic methods. The microstructures displayed conductivities
of 3.8 × 10–1 S/cm upon HCl doping and 1.5
× 10–1 S/cm upon H2SO4 doping, on par with state-of-the-art patterning methods. High fidelity
control over the width of the printed lines down to ∼650 nm
was accomplished by varying the laser power and microscope stage velocity.
This straightforward bottom-up method using low-power lasers offers
an alternative to current microfabrication techniques.
Assembly of materials into microstructures under laser guidance is attracting wide attention. The ability to pattern various materials and form 2D and 3D structures with micron/sub‐micron resolution and less energy and material waste compared with standard top‐down methods make laser‐based printing promising for many applications, for example medical devices, sensors, and microelectronics. Assembly from liquids provides a smaller feature size than powders and has advantages over other states of matter in terms of relatively simple setup, easy handling, and recycling. However, the simplicity of the setup conceals a variety of underlying mechanisms, which cannot be identified simply according to the starting or resulting materials. This progress report surveys the various mechanisms according to the source of the material—preformed or locally synthesized. Within each category, methods are defined according to the driving force of material deposition. The advantages and limitations of each method are critically discussed, and the methods are compared, shedding light on future directions and developments required to advance this field.
Micro-patterning of a metal organic framework (MOF) from a solution of precursors is achieved by local laser heating, alleviating the need for pre-preparation and stabilization.
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