Laser-direct writing has become an alternative method to fabricate flexible electronics, whereas the resistive nature of laser-scribed conductors may distort the radio-frequency characteristics of circuits for high-frequency applications. We demonstrate that the transmission characteristics of microstrip lines are insensitive to the resistance of laser-scripted conductors when the sheet resistance is not above 0.32 Ω/ . On the other hand, the transmission and reflection characteristics of the MS lines can be simply modified through the accommodation of the resistance of the conductors, because a laser can trigger the sintering and melting of laser produced silver nanostructures. This could provide an alternative way to fabricate radio frequency (RF) resistors and promote their applications to flexible radio-frequency devices and systems.

Microcrack is commonly seen as a defect in materials that affects the performance of flexible radio frequency (RF) devices. Here, we investigate the influence of microcracks on the RF characteristics of flexible microstrip by stretching flexible microstrip that is based on polydimethylsiloxane (PDMS) substrate and an Ag microparticles/PDMS (AgMP/PDMS) composite conductor. The RF characteristics of the microstrip were monitored with a variety of tensile displacements. An equivalent circuit model of the microstrip with microcracks was proposed to reveal the mechanisms. The fitting results matched the actual measurement well. In addition, the morphology of the microcracks was characterized by SEM and the direct-current (DC) resistance was monitored. The results show that the changes in equivalent circuit element parameters (R, L, C) are due to the change in the conductive pathways, which affect the transmission and reflection of the RF signals.

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Photothermal microactuators are often used as microswitches or microgrippers in micro-electromechanical systems, whereas it is difficult to fabricate three-dimensional microactuators with a high aspect ratio, since the gravity may lead to undesired deformations during printing processes. In this work, we reported a 3D printing / UV curing process flow in the support of a hydrogel to obtain a photothermal microactuator with a high-aspect-ratio polyline waveguiding structure. The waveguiding structure also served as the driving arm. The temperature parameter was investigated by the Finite Element Method while the experiment was carried out to study the temperature and displacement during the laser actuation. A demonstration showed the driving arm achieves a free-end displacement of 133.2 µm driven by 90 mW laser (46.1°C). This study helps obtain waveguiding photothermal microactuators with integrated and more complex multi-dimensional structures.