In recent years, metal nanowiring for circuitry and electronic interconnection has attracted much attention due to the growing requirements of highly integrated microcircuits, and is of benefit to the miniaturization of device features. [1] Generally, ultraviolet photolithography, which was considered a typical processing route for metal wiring, has already greatly contributed to integrated circuits. [2] However, the lithographic route shows strong demands on the surface flatness of each layer in the multilevel chip architectures. To meet the processing nature of lithography, a global planarization of interlayer metals by chemical-mechanical polishing is therefore needed to reduce the interval between the metal layer and the photomask, and to guarantee exposure resolution when wires reach the sub-300 nm scale. Two-photon absorption (TPA) has also been tried for the fabrication of metal microstructures by using suitable salt solutions as the metal source and photosensitive molecules as the photoinitiator. [3][4][5] However, these studies aimed at refined planar periodic gratings or dot arrays [6] for plasmonic wave coupling or three-dimensional (3D) mold making, which more or less ignore the conductivity of these precise metal structures. For example, by using surfactants as particle-growth inhibitor, delicate 3D structures with a smooth surface were achieved, [7] whereas the conductivity of these metal microstructures was significantly debased due to the residual organic components.To the best of our knowledge, both the photolithography and TPA micro/nanoprocessing conducted so far have focused on fabrication on flat substrates. [8][9][10] These methods cannot meet the increasing demands of circuitry and electronic connections on nonplanar substrates in microelectromechanical systems (MEMS), [1] lab on a chip (LoC), [11] and other intelligent microsystems. Taking LoC as an example, if an appropriate microheater could be embedded on the immediate base inside a microfluidic channel instead of sitting several hundreds of micrometers apart on the rear of the substrate, as is usually done with Peltier thermoelectric elements, [12] integrated resistive heaters, [13][14][15][16][17] and Joule heating of ionic liquids, [18] then local temperature regulation of fluids with higher precision, quicker response, and smarter switching at the exact point of care may be realized due to the effectively reduced thermal inertia. Such a capability is particularly desired for temperature regulation of miniaturized LoC systems that involve repeated thermal cycling, such as DNA amplification by the polymerase chain reaction (PCR), which comprises three sequential steps of denaturation (95 8C), annealing (55 8C), and extension (72 8C). [12] Nevertheless, convenient introduction of a local heating circuit inside a ready channel is almost inaccessible for lithography and other currently available micro/nanofabrication methods. Therefore, there is an urgent need for flexible micro/nanoprocessing technologies for metal nanowiring on nonplan...

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Performances of the metal-to-metal contact radio frequency (RF) MEMS switches largely rely on the contacts. A novel contact employing the microspring structure is demonstrated in this paper. The microspring contact can achieve a stable contact at lower actuation voltage, alleviating mechanical wear on the contacts, and can effectively increase the fabrication tolerance. An in-line Pt–Au microspring contact switch was fabricated and characterized. To evaluate the improvement in performance, the results were compared with those of the Au–Au solid contact switch without a microspring design. The highest current handled by the Pt–Au microspring contact was 150 mA per contact, whereas only 20 mA was handled by the Au–Au solid contact. The insertion loss of the Pt–Au microspring contact switch was –0.2 dB at 20 GHz, which was comparable with that of the Au–Au solid contact switch. The isolation of the Pt–Au microspring contact switch was –22 dB at 20 GHz, and that of the Au–Au solid contact switch was –18 dB. With the Pt–Au microspring contact, the switch exceeds its power handling ability and reliability with comparable RF performances.