In this paper we report a simple and effective method that renders direct imprinting of sub-micron structures onto PMMA resist coated on large area and curved substrates using the PDMS mold on a closed chamber. Nitrogen gas was employed to generate a uniform pressure. The patterns of the soft mold could be replicated with high quality over an entire 12 in. resist-coated area. The process was further successfully applied to the imprinting of a curved substrate.

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With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 µW and 12.5 µW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems.Currently, most vibrational energy harvesters (VEHs) are usually designed as resonance systems for higher power output. However, one of the main problems for VEHs with the resonant behavior is the narrow operating bandwidth. Thus, when operated under irregular mechanical vibration sources with low and variable frequencies, most VEHs yield very low and irregular output power, which lowers their practical application possibilities.To solve the problem of narrow bandwidth, many researchers have demonstrated some broadband harvesters by applying multimodal harvesting technique [17][18][19][20][21][22][23]. Multimodal energy harvesters are considered more efficient in matching multiple frequencies to better utilize kinetic energy. Sari et al. [17], Liu et al. [18], and Qi et al. [19] reported the use of multiple cantilevers or a cantilever array as one solution to increase the bandwidth. However, this type of energy harvester has the disadvantage of being bulky and complex in structure, thus overshadowing its advantages in broadband behavior. Another multimodal system was developed with multiple bending modes in a continuous beam, rather than using arrays of cantilevers configuration [20][21][22][23]. Ou et al. presented a broadband energy harvester with a two-mass cantilever beam structure [20]. Due to the addition of an extra mass, two useful working modes can be obtained. Arafa et al. developed a two-degree-of-freedom (2DOF) cantilever-based piezoelectric generator which used the proof mass as a dynamic amplifier [21]. However, the multimodal harvester only increases the number of peak amplitudes, and the bandwidth of each peak is relatively narrow, which still causes a sharp drop in power generation when the excitation...

A gasbag pressure (GBP) mechanism has been developed for patterning submicron patterns onto large concave substrate. The GBP mechanism consists of a pressure gasbag and a vacuum chamber system. It provides gradual contact, uniform pressure, and intact contact for imprinting patterns in the soft mold onto a concave substrate. The patterns on the soft mold can be successfully replicated over an entire photoresist-coated concave substrate. The accuracy of replication has been experimentally evaluated.

Articles you may be interested inMechanical characterization of a piezo-operated thermal imprint system J. Vac. Sci. Technol. B 29, 06FC13 (2011); 10.1116/1.3656048 Micro-and nanopatterned polymethylmethacrylate layers on plastic poly(ethylene terephthalate) substrates by modified roller-reversal imprint process J. Vac. Sci. Technol. B 28, 921 (2010); 10.1116/1.3474984 Sub-200 nm gap electrodes by soft UV nanoimprint lithography using polydimethylsiloxane mold without external pressure J. Vac. Sci. Technol. B 28, 82 (2010); 10.1116/1.3273535Direct UV-imprint lithography using conductive nanofiller-dispersed UV-curable resin This article reports a novel hydrostatic pressure mechanism for soft UV imprinting. With this mechanism, the pressure distribution over the whole substrate is uniform. In addition, the nonuniform deformation of the soft mold during the imprinting process can be avoided. The mechanism employs a gasbag inside a closed chamber, which upon inflation compresses the whole polydimethylsiloxane ͑PDMS͒ mold/substrate stack not only from the surface but also from all the sides. The microstructures on the PDMS mold are then replicated onto photoresist-coated substrates. The result shows that the soft UV imprinting using a hydrostatic pressure mechanism can provide uniform pressure for imprinting. It also provides the hydrostatic pressure state on the stack so that micropatterns can be replicated with high fidelity from soft mold to photoresist on substrates. The accuracy of replication, even at the edge, has been experimentally verified.