Thermochemical decomposition of organic materials under heat-treatment in the absence of oxygen, known as the pyrolysis process, is often employed to convert micro and nano patterned polymers into carbon structures, which are subsequently used as device components. Pyrolysis is performed at ≥900 °C, which entails substrate materials with a high thermal stability that excludes flexible, polymeric substrates. We use optimized laser radiation to pattern graphitic carbon structures onto commercially available polyimide (Kapton) sheets in the micrometer to millimeter scale by inducing a localized, rapid pyrolysis, for the fabrication of flexible devices. Resulting laser carbon films are electrically conductive and exhibit a high-surface area with a hierarchical porosity distribution along their cross-section. The material is obtained using various combinations of laser parameters and pyrolysis environment (oxygen-containing and inert). Extensive characterization of laser carbon is performed to understand the correlation between the material properties and laser parameters, primarily fluence and power. A photothermal carbonization mechanism based on the plume formation is proposed. Further, laser carbon is used for the fabrication of enzymatic, pH-based urea sensors using two approaches: (i) direct urease enzyme immobilization onto carbon and (ii) electrodeposition of an intermediate chitosan layer prior to urease immobilization. This flexible sensor is tested for quantitative urea detection down to 10⁻⁴ M concentrations, while a qualitative, color-indicative test is performed on a folded sensor placed inside a tube to demonstrate its compatibility with catheters. Laser carbon is suitable for a variety of other flexible electronics and sensors, can be conveniently integrated with an external circuitry, heating elements, and with other microfabrication techniques such as fluidic platforms.

Low-cost enzyme-free glucose sensors with partial flexibility adaptable for wearable Internet of Things devices that can be envisioned as personalized point-of-care devices were produced by electroplating copper on locally carbonized flexible meta-polyaramid (Nomex) sheets using laser radiation. Freestanding films were annealed in nitrogen and nitrogen/air working environments, leading to the formation of Cu microspheroids and CuO urchins dispersed on the substrate film. The aggregation mechanism, crystallographic properties, surface chemistry, and electrochemical properties of the films were studied using scanning electron microscopy, X-ray diffractometry, transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. Cu microspheroids and CuO urchins attained activity for glucose detection and showed improvement of amperometric sensitivity to 0.25 and 0.32 mA cm^–2 mM^–1, respectively. The CuO urchin film retained its chemical composition after amperometric testing, and, by rinsing, allowed multiple repetitions with reproducible results. This study opens the possibility for the fabrication of durable composite biosensors with tailored shape, capable of implementation in flexible carriers, and microfluidic systems.

A method for the fabrication of flexible electrical circuits on polyaramid substrates is presented based on laser-induced carbonization followed by copper electroplating. Locally carbonized flexible sheets of polyaramid (Nomex), by laser radiation, create rough and highly porous microstructures that show a higher degree of graphitization than thermally carbonized Nomex sheets. The found recipe for laser-induced carbonization creates conductivities of up to ∼45 S cm^–1, thereby exceeding that observed for thermally pyrolyzed materials (∼38 S cm^–1) and laser carbon derived from Kapton using the same laser wavelength (∼35 S cm^–1). The electrical conductivity of the carbonized tracks was further improved by electroplating with copper. To demonstrate the electrical performance, fabricated circuits were tested and improvement of the sheet resistance was determined. Copper films exhibit antimicrobial activity and were used to fabricate customized flexible antibacterial coatings. The integration of laser carbonization and electroplating technologies in a polyaramid substrate points to the development of customized circuit designs for smart textiles operating in high-temperature environments.

To date, thermal nanoimprint lithography (NIL) for patterning hybrid perovskites has always involved an intricate etching step of a hard stamp material or its master. Here, we demonstrate for the first time the successful nanopatterning of a perovskite film by NIL with a low-cost polymeric stamp. The stamp consists of a dichromated gelatin grating structured by holographic lithography. The one-dimensional grating is imprinted into a perovskite film at 95 °C and 90 MPa for 10 min, resulting in a high quality second-order distributed feedback (DFB) laser. The laser exhibits an excellent performance with a threshold of 81 μJ/cm², a line width of 0.32 nm, and a pronounced linear polarization. This novel approach enables cost-effective fabrication of high-quality DFB lasers compatible with different perovskite compositions and photonic nanostructures for a wide range of applications.

This paper presents the results of a comprehensive study of the pull-in phenomenon in the hybrid levitation microactuator (HLMA), in which square-shaped proof masses (PMs) of different sizes, namely, length sides of 2.8 and 3.2 mm and thicknesses of 25 and 10 μm were electromagnetically levitated. The pull-in actuation of the square-shaped PMs was performed by the electrostatic force generated by the set of energized electrodes and acting on the bottom surface of the PMs along the vertical direction. The pull-in parameters, such as pull-in displacements and the corresponding applied pull-in voltages, were measured with the developed setup. The experimental measurements showed that the pull-in actuation is nonlinearly dependent on the size and mass of the PMs and a levitation height. In particular, it was found that PMs levitated within a height range from 140 to 170 μm can be stably displaced within a range of 30 μm. The results of measurements were extensively simulated with the developed analytical model by means of the quasi-FEM method. The direct comparison of the results of simulation and measurements showed a very good agreement between the theory and experiments.