The laser-induced microbubble technique (LIMBT) has recently been developed for micro-patterning of various materials. In this method, a laser beam is focused on a dispersion of nanoparticles leading to the formation of a microbubble due to laser heating. Convection currents around the microbubble carry nanoparticles so that they become pinned to the bubble/substrate interface. The major limitation of this technique is that for most materials, a noncontinuous deposition is formed. We show that continuous patterns can be formed by preventing the microbubble from being pinned to the deposited material. This is done by modulating the laser so that the construction and destruction of the microbubble are controlled. When the method is applied to a dispersion of Ag nanoparticles, continuous electrically conductive lines are formed. Furthermore, the line width is narrower than that achieved by the standard nonmodulated LIMBT. This approach can be applied to the direct-write fabrication of micron-size conductive patterns in electronic devices without the use of photolithography.

Laser‐induced photothermal reaction of metal ions is a promising one‐step method for production of conductive micropatterns for electronic devices and sensors. However, the mechanism that governs the process in which thermally activated materials are deposited on a substrate is not clear. Here, light is shed on the mechanism through systematic analysis of photothermal reaction products forming iron oxide and silver at different interfaces. Examination of the nanostructure of deposits on a substrate using high‐resolution transmission electron microscopy and selected area diffraction pattern analysis reveals a combination of both amorphous and crystalline moieties. It is found that focusing the laser inside the solution leads to exclusive formation of crystalline products, while focusing at the liquid/air interface leads to formation of amorphous products due to kinetic considerations. Ring‐shaped microstructures observed on the substrate indicate that microbubbles are involved in the deposition. The findings suggest that crystalline nanoparticles formed in solution are pinned to the base of the microbubbles. These stationary deposits absorb the laser light, resulting in extensive local heating, which leads to a fast thermal‐reaction of the metal ions that are added as amorphous nanostructures. The presence of both crystalline and amorphous nanostructures therefore results from two different mechanisms.

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.