In this paper, we demonstrate the fabrication and characterization of bistable piezoelectric plates with a precisely tuned residual stress to achieve buckling-induced bistability. The plate consist of a multilayered structure, with a piezoelectric aluminum nitride layer sandwiched between top and bottom electrode layers. The stress in the aluminum nitride thin film is tuned by adjusting the DC magnetron sputtering parameters, including sputtering pressure, gas flow rates, target-substrate distance, and substrate bias voltage to introduce the compressive stress needed to induce plate buckling. Experimental results demonstrate that reducing sputtering pressure while controlling nitrogen flow, with no argon admixture, and applying a substrate bias voltage above 10 V enables compressive stress in the aluminum nitride layer within the desired range of -800 to -600 MPa, resulting in bistable plates. The bistability of the fabricated plates is evaluated by analyzing their potential energy profiles under applied external perpendicular forces, using a bulge test setup, where uniform air pressure is applied to the plate surface. The plates exhibit a characteristic hysteresis loop in their load–deflection response, with transitions between buckled-down and buckled-up states at approximately 10 mbar and -30 mbar, respectively. The initial buckling amplitude of the fabricated plates, within the optimized stress range, is measured to be 5-7 μ m, with a total displacement of 10-12 μ m when switching between both states. Furthermore, in each stable state, the plates exhibit an additional displacement of approximately 5 μ m when subjected to a relative air pressure of ∼ 1 bar. • Stress tuning in AlN layers enables bistability in piezoelectric plates. • Compressive stress in AlN induced via sputtering parameter control. • Experimental load–deflection reveals bistability with buckling amplitudes of ∼ 7 μ m. • Residual stress and asymmetry estimated from experimental potential energy profile.

Masking of thin films and bulk materials is traditionally applied for the transfer of micron patterns into the functional material according to the requirements of the application. For optical purposes, lithographically produced micron patterns are transferred by plasma/ion etching, which is a traditional technology in microelectronics and other micron technologies. However, pattern transfer by atmospheric pressure plasma etching can help to save time and cost for a future sustainable production. Therefore, the pattern transfer of lithographic resist masks into fused silica using atmospheric pressure reactive plasma jets (APPJ) was studied as a new approach of micropatterning. First the etch rates of the potential masking materials, e.g. photoresists, as well as of fused silica as substrate are studied in dependence on the APPJ etching parameters, in particular on the gas composition (O 2 /CF 4 ) and the dwell time of the APPJ tool's footprint. Typical etch rates of the masking materials are in the range of 140 to 370 nm·s −1 whereas the fused silica has a rate of 25 to 80 nm·s −1 . The surface morphology of masking materials changes during etching and features additional nanoscale roughness and waviness. The surface roughness of the etched masking materials and the fused silica are 2 to 5 nm rms and 1.5 nm rms for etch depths of ~3000 nm and ~ 600 nm, respectively. Finally, the pattern transfer by APPJ of a diffraction grating with a period of 15 μm, depth of 230 nm and a roughness below 2 nm rms into fused silica was demonstrated. • Lithographic pattern transfer by APPJ etching is demonstrated for the first time. • Roughness of 5 nm at etching depth of 3 μm for polymers and 2 nm at 600 nm for SiO 2. • Pattern transfer of a diffraction grating into fused silica by APPJ etching shown. • Selectivity of SiO 2 /Resist is adjustable by the APPJ gas composition.

In this study, a method for depositing and patterning the thermosensitive polymer poly(N-isopropylacrylamide) on SiO2 surfaces is presented for potential use in nano-sized microfluidic channels. Two approaches based on nanolithographic processes are shown for this purpose. In both cases, a self-assembling monolayer consisting of (3-aminopropyl)-dimethylethoxysilane was bound to the hydroxyl group of the substrate surface and subsequently functionalized with the polymerization initiator α-bromoisobutyryl bromide. In the first approach the silane monolayer itself was patterned using a photoresist and a lift-off process, followed by the selective deposition of the initiator, which starts a substrate-induced atom transfer radical polymerization for the growth of polymer on the silane monolayer. In the second approach, the lift-off takes place after the polymerization on the substrate surface. The result of this study shows the successful application of the process steps for the nano-dimensioned grafting of poly(N-isopropylacrylamide) onto SiO2 substrates. The reaction time of the silane monolayer with the polymerization initiator and the composition of the reaction solution used were found to have the greatest influence of the processes. AFM and XPS analysis of the functionalized surfaces revealed patterned growth of both the self-assembling monolayer and the polymer structures.