Multi-walled microchannels: free-standing porous silicon membranes for use in µTAS

Electrochemically formed porous silicon (PS) can be released from the bulk silicon substrate by underetching at increased current density. Using this technique, two types of channels containing free-standing layers of PS were constructed, which were failed multi-walled microchannels (MW µCs). They can be used in devices like microsieves, microbatteries, and porous electrodes. Two types of MWµC were made: the 'conventional' version, consisting of two or more coaxially constructed microchannels separated by a suspended PS membrane, and the buried variety, where a PS membrane is suspended halfway in an etched cavity surrounded by silicon nitride walls. The latter is more robust. The pore size of the PS was measured using transmission electron microscopy and field emission gun scanning electron microscopy (FEGSEM) and found to be of the order of 7 n

Local deposition and patterning of catalytic thin films in microsystems

The local deposition of catalysts is desired in a wide range of catalytic microsystems (microreactors and sensors). In this study, we investigate technologies enabling deposition and patterning of catalyst thin films in a manner compatible with standard micromachining processes. We evaluate and compare deposition techniques based on a combination of a self-assembly, soft-lithography and conventional micromachining. Platinum (Pt) and palladium (Pd) were used as model catalysts, both as a sputtered thin film and as nanoparticles supported on γ-alumina. The thin films were characterized and tested in terms of their catalytic activity based on CO chemisorption measurements, stability and reproducibilit

A chemoemitter system mimicking chemical communication in insects

AbstractThe first chemoemitter based on the concept of infochemical communication is presented emphasizing details on the microfabrication and functionality of its elements, particularly the biomicroreactor and the evaporator. The functionality of the integrated chemoemitter has been evidenced in electrophysiological assays using antennae from Spodoptera littoralis males for pheromone detection and quantification

Additive manufacturing of 3D yttria-stabilized zirconia microarchitectures

The additive manufacturing (AM) of yttria-stabilized zirconia (YSZ) microarchitectures with sub-micrometer precision via two-photon lithography (TPL), utilizing custom photoresin containing zirconium and yttrium monomers is investigated. YSZ 3D microarchitectures can be formed at low temperatures (600 °C). The low-temperature phase stabilization of ZrO2 doped with Y2O3 demonstrates that doping ZrO2 with ≈ 10 mol% Y2O3 stabilizes the c-ZrO2 phase. The approach does not utilize YSZ particles as additives. Instead, the crystallization of the YSZ phase is initiated after printing, i.e., during thermal processing in the air at 600 °C – 1200 °C for one and two hours. The YSZ microarchitectures are characterized in detail. This includes understanding the role of defect chemistry, which has been overlooked in TPL-enabled micro-ceramics. Upon UV excitation, defect-related yellowish-green emission is observed from YSZ microarchitectures associated with intrinsic and extrinsic centers, correlated with the charge compensation due to Y3+ doping. The mechanical properties of the microarchitectures are assessed with manufactured micropillars. Micropillar compression yields the intrinsic mechanical strength of YSZ. The highest strength is observed for micropillars annealed at 600 °C, and this characteristic decreased with an increase in the annealing temperature. The deformation behavior gradually changes from ductile to brittle-like, correlating with the Hall–Petch strengthening mechanism.</p

Three-phase mass transfer in pillared micro channels

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