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A low-cost method of fabrication of high aspect ratio nano-channels by thermal nano-imprinting and Parylene deposition is proposed. SU-8 photoresist nano-channels were first manufactured by thermal nano-imprinting, and Parylene deposition was carried out to reduce the width of the nano-channels and increase the aspect ratio. During the process, the side walls of the SU-8 nano-channels were covered with the Parylene film, reducing the width of the nano-channels, and the depth of the channels increased due to the thickness of the Parylene film deposited on the surface of the SU-8 nano-channels, more so than that at the bottom. The influence of Parylene mass on the size of nano-channels was studied by theoretical analysis and experiments, and the deposition pressure of Parylene was optimized. The final high aspect ratio nano-channels are 46 nm in width and 746 nm in depth, of which the aspect ratio is 16. This simple and efficient method paves the way for the production of high aspect ratio nano-channels. [ABSTRACT FROM AUTHOR]

For a structure to show radiative cooling property, it must have first, high reflectivity of above 90% in the wavelength range of 0.3 to 3 μm, and second, high emissivity for the wavelengths ranging from 8 to 13 μm, namely atmospheric transparency window. Being inspired by the architecture of microwave absorbers used extensively for antenna measurements, we proposed a novel microstructure with near unity emissivity that can be further developed for radiative cooling. To this end, we designed and analyzed a V-grooved multilayer periodic microstructure capable of perfectly emitting in the aforementioned wavelength range. Further, SU-8 is selected as the material of the proposed microstructure. SU-8 is the commonly used material in photolithographic based microfabrication and it is shown, for the first time, that its bulk optical properties are appropriate for radiative cooling purposes. The numerical simulations of the emissivity were performed through a semi-analytical computational technique known as Transmission-Line Formulation (TLF) which enables us to accurately and efficiently calculate electromagnetic radiations reflected from or transmitted through a multilayer structures composed of periodic layers of absorbing materials. It was demonstrated through the simulations that the average emissivity of the proposed microstructure can even exceed 99% in the wavelength range desired for radiative cooling.

To solve the problem of shaping nonspecialized polymers, new generation micro- and nanoelectronic technologies are used, for example, nanoimprint lithography. A special case of nanoimprint lithography is soft lithography, which involves the formation of a topology using a soft master mold fabricated by a hard mold imprint. Therefore, the study of hard molds self-manufacturing possibility is an urgent task to fabricate a new generation printed circuit boards with optoelectronic buses made of nonspecialized polymer materials. In order to rationalize the cost of purchasing an expensive soft lithography hard mold, an original technological process for hard mold fabrication based on an SU-8 photoresist is developed and implemented. During the development of the proposed technological process, the reason for the formation of a negative slope (T-topping) of the walls of the soft lithography hard mold is determined. In order to eliminate the negative slope, a series of UV cutoff filters for optical radiation wavelengths less than 350 nm is developed and manufactured. According to the experimental measurements data of the i-line mercury lamp UV radiation intensity of the EVG620 NIL automated alignment and exposure unit, the dependences of the UV radiation intensity attenuation on the developed UV light filter functional layer thickness are plotted for 365 and 400 nm optical wavelengths. The effectiveness of the use of the developed UV filters is proved by eliminating the negative slope during the technological process of manufacturing a test topology of the soft lithography hard mold. Soft lithography will make it possible in the future to create printed circuit boards with a built-in optoelectronic data bus in the form of an array of polymer planar optical waveguides and optical input-output elements. [ABSTRACT FROM AUTHOR]

• Introduce a novel fabrication method to design optical cavity with SU-8 photoresist. • The optical cavity can localize wave around 1269.3 nm, and the Q factor in the cavity is comparatively higher. • The smaller thickness of SU-8, the higher quality factor Q value can be obtained. • Experiment showed that a high quality factor of Q = 8200 could be obtained. How to control electromagnetic wave effectively is the key to the realization of applicable filters in many optics technologies. In our work, a SU-8 photoresist micro-disk is written onto a photonic crystal waveguide to control electromagnetic wave. Corresponding simulation and experiment shows that, the quality Q increases as the thickness of SU-8 smaller. When the thickness exceeds 400 nm, the change of thickness has little influence on electromagnetic waves. Besides, the increase of the radius of disc-shaped SU-8 can also increase the Q value. By optimizing the simulation and experimental data, we can successfully create a SU-8 photoresist micro-disk cavity with the thickness of 5 µm and height of 20 nm, the quality factor of Q can reach 8200. However, longer exposure time and more stable experimental equipment is needed if we want to get a larger radius. The method in our work by using SU-8 photoresist micro-disk on photonic crystals to control electromagnetic wave is more practical and flexible, which can provide new significance for research into optical filter. [ABSTRACT FROM AUTHOR]

This paper investigates the fabrication accuracy of the W-band SU-8 photoresist micromachined 4th order waveguide bandpass filters (BPF). The designed filter based on cylindrical resonators is excited in TM010 mode. It is ideally suitable for the layered SU-8 micromachining process as the height of the resonator is much smaller than one wavelength, the electromagnetic fields remain unchanged in the thickness direction. The filter is composed of three silver-coated SU-8 layers based on a double-layer overlay process. Excellent manufacturing tolerances can be controlled within 4 μm in the thickness direction, around 10 μm in double-layer stacking accuracy, and an average of 1° in vertical angle deviation. Various challenges encountered in the SU-8 process are investigated while corresponding general solutions are proposed for machining high-precision devices. The measured results show a return loss of 12.4 dB and a minimum insertion loss of 0.8 dB, which are in agreement with the simulated one. Stress and deformation analysis are also conducted to confirm the maximum pressure that the filter can withstand and maintain good transmission performance. [ABSTRACT FROM AUTHOR]

A low-cost method of fabrication of high aspect ratio nano-channels by thermal nano-imprinting and Parylene deposition is proposed. SU-8 photoresist nano-channels were first manufactured by thermal nano-imprinting, and Parylene deposition was carried out to reduce the width of the nano-channels and increase the aspect ratio. During the process, the side walls of the SU-8 nano-channels were covered with the Parylene film, reducing the width of the nano-channels, and the depth of the channels increased due to the thickness of the Parylene film deposited on the surface of the SU-8 nano-channels, more so than that at the bottom. The influence of Parylene mass on the size of nano-channels was studied by theoretical analysis and experiments, and the deposition pressure of Parylene was optimized. The final high aspect ratio nano-channels are 46 nm in width and 746 nm in depth, of which the aspect ratio is 16. This simple and efficient method paves the way for the production of high aspect ratio nano-channels.

This paper investigates the fabrication accuracy of the W-band SU-8 photoresist micromachined 4th order waveguide bandpass filters (BPF). The designed filter based on cylindrical resonators is excited in TM010 mode. It is ideally suitable for the layered SU-8 micromachining process as the height of the resonator is much smaller than one wavelength, the electromagnetic fields remain unchanged in the thickness direction. The filter is composed of three silver-coated SU-8 layers based on a double-layer overlay process. Excellent manufacturing tolerances can be controlled within 4 μm in the thickness direction, around 10 μm in double-layer stacking accuracy, and an average of 1° in vertical angle deviation. Various challenges encountered in the SU-8 process are investigated while corresponding general solutions are proposed for machining high-precision devices. The measured results show a return loss of 12.4 dB and a minimum insertion loss of 0.8 dB, which are in agreement with the simulated one. Stress and deformation analysis are also conducted to confirm the maximum pressure that the filter can withstand and maintain good transmission performance.

We demonstrate GaAs thermophotovoltaic (TPV) devices with a patterned dielectric back contact (PDBC) architecture, featuring a dielectric spacer between the semiconductor and back metal contact over most of the back surface for high reflectance, and metal point contacts over a smaller area for electrical conduction. In the TPV application, high sub-bandgap reflectance is needed to reflect unused sub-bandgap photons to the thermal emitter to minimize energy losses in this portion of the thermal spectrum. We explore different PDBC fabrication processes with SU-8 and SiO 2 dielectric spacer layers to maximize sub-bandgap reflectance while minimizing series resistance to increase TPV conversion efficiency. We successfully demonstrate GaAs SU-8 PDBC TPV devices with 2200 °C blackbody-weighted sub-bandgap reflectance of 94.9% and 96.5% with and without a front metal grid, respectively. This is 0.7% and 2.3% (absolute) higher than the mean sub-bandgap reflectance of 94.2% for GaAs baseline TPV devices with 100% Au back contact with front metal grid. Lower sub-bandgap reflectance in TPV devices with front grids indicates the front grid induces light scattering leading to additional parasitic absorption in the TPV device. We also show that for higher contact coverage fractions, the PDBC reflectance cannot in general be treated by a linear interpolation using simple 1D transfer matrix method modeling and should be treated instead as a diffraction grating by solving Maxwell's equations in 3D. • We explore different patterned dielectric back contact (PDBC) fabrication processes with SU-8 and SiO 2 for TPV cells. • Sub-bandgap reflectance over 96% demonstrated using dielectric-metal point contact rear mirror structure, a gain of >1%. • PDBC structures should be modeled as a 3-dimensional diffraction grating by solving Maxwell's equations. • Front grids increase diffuse reflectance thus increasing absorption in the device. [ABSTRACT FROM AUTHOR]

• Graphene functionalized microelectrode array chip was fabricated by an in situ modification method easily on carbonized SU-8 photoresist. • The in situ generated graphene modified microelectrode array (GC-MEA) showed stronger impedance signals due to the higher bacterial load and preferable microenvironment. • It was verified the impedimetric sensor present high specificity towards bacterial biofilms. • The GC-MEA was found to be effective for developing a drug screening platform in dealing with detrimental biofilms. Microbial films, formed by the microorganisms to adapt to their living environment, are closely related to the drug resistance and persistent infection of certain diseases such as gingivitis. Impedimetric biosensors could provide an effective means to study the biofilm formation and screening antibiofilm drugs, their performance is closely dependent on the interface materials used thereon. Here, we report a sensitive biosensor platform for this purpose by integration of graphene with carbon microelectrode arrays (C-MEA). A C-MEA was obtained on a silicon substrate through photolithography and subsequent pyrolysis. Characterized by scanning electron microscopy (SEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electrochemical, we verified that the C-MEAs could evolve into an electrochemically in situ graphene-modified form, GC-MEAs. Using GC-MEA, the growth of biofilm of S. mutans was successfully monitored. Compared to C-MEAs and conventional macrosized counterparts, significant impedance signal amplification and wider detectable frequency range were achieved on the GC-MEAs. Besides, we demonstrated the impedance sensing technology presents high specificity towards the interface-stacked biofilm. The increase in impedimetric signal on the GC-MEAs was 1.4∼2.1 times stronger than that of the C-MEAs and 12.2–13.9 times that of the macrosized electrodes with biofilm growth at a detection frequency of 10.0 kHz. In the last part, the destruction of biofilms grown on the GC-MEAs by using cetylpyridinium chloride was readily monitored by the GC-MEAs senor. In general, graphene-based microelectrode arrays show promise for developing high-throughput drug screening platforms for dealing with detrimental biofilms. [Display omitted] [ABSTRACT FROM AUTHOR]