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In an effort to directly manufacture devices with embedded complex and three‐dimensional (3D) micro‐channels on the order of microns to millimeters, issues associated with micro‐fabrication using current commercially available line‐scan stereolithography (SL) technology were investigated.

Practical issues associated with the successful fabrication of embedded micro‐channels were divided into software part preparation, part manufacture, and post‐cleaning with emphasis on channel geometry, size, and orientation for successful micro‐fabrication. Accurate representation of intended geometries was investigated during conversion from CAD to STL and STL to machine build file, and fabricated vertical and horizontal micro‐channels were inspected. Additional build issues investigated included accurate spatial registration of the build platform, building without base support, and Z‐stage position accuracy during the build.

For successful fabrication of micro‐channels using current technology, it is imperative to inspect the conversion process from CAD to STL and STL to machine build file. Inaccuracies in micro‐channel representation can arise at different stages of part preparation, although newer software versions appear to improve representation of micro‐geometries. Square channel cross‐sections are most easily sliced and vertical channels are most easily stacked together for layered manufacturing. While building, a means should be developed for building without base and internal supports, providing feedback on Z‐stage position, and having the capability for cleaning the micro‐channels.

This research demonstrates that commercial SL technology is capable of accurately fabricating embedded vertical square cross‐section micro‐channels on the order of 100 μm (with reasonable advancements to smaller scales on the order of 10 μm achievable). Additional practical limitations exist on other channel geometries and orientations. The research used a single resin and additional material resins should be explored for improved micro‐fabrication characteristics.

Practical issues associated with micro‐fabrication of embedded channels with appropriate solutions using available SL technology were provided. It is expected that these solutions will enable unique applications of micro‐channel fabrication for micro‐fluidic and other devices.

This work represents an original investigation of the capabilities of current line‐scan SL technology for fabricating embedded micro‐channels, and the solutions provide the means for applying this technology in micro‐fabrication.

The micro-vision system is designed for micro-fabrication. This system with force sensor controls micro-fabrication operation. The focus is calculated by one order moment. Gradient evaluation function and frequency domain evaluation function are combined as evaluation function in auto-focus technology. Image definition evaluation function based on gradient is adopted in large step. Image definition evaluation function based on frequency-domain is adopted in small step. Search strategy adopts threshold method and curve fitting method. Edge invariant moment is to recognize objects. The system can measure the distance of three dimensions between the cutting tool and the work-piece. Then the micro-fabrication operation is completed.

We report on micro fabrication methods used to integrate electronics into smart textiles. We have introduced a shadow mask fabrication method to pattern 2D thin film structures onto the 3D surface of yarn. We have demonstrated the fabrication of gold resistance temperature sensors (RTDs) onto 500 μm thick nylon yarn. The sensors are meander shaped and have lateral dimensions of 0.3 mm × 1 mm and the width and spacing of the meander is 20 μm. Two different fabrication methods are developed and evaluated: 1) a planar mask made of Kapton foil is patterned by dry etching and 2) a tube mask made of Kapton foil is patterned with a laser. Both methods have proven to be suitable for the fabrication of RTDs onto textile yarns. The fabricated sensors are measured in a climate chamber from 15 to 50°C. The temperature coefficient of the RTDs is 0.0026 ω/°C with a sensitivity of 0.74 ω/°C.

The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three‐dimensional (3D) micro‐parts with a previously developed dynamic mask projection microstereolithography (MSL) system. A common issue with stereolithography systems and especially important in MSL is uncontrolled penetration of the ultraviolet light source into the photocrosslinkable resin when fabricating down‐facing surfaces. To accurately fabricate complex 3D parts with down‐facing surfaces, a chemical light absorber, Tinuvin 327™ was mixed in different concentrations into an acrylate‐based photocurable resin, and the solutions were tested for cure depths and successful micro‐part fabrication.

Tinuvin 327 was selected as the light absorber based on its high absorption characteristics (∼0.4) at 365 nm (the filtered light wavelength used in the MSL system). Four concentrations of Tinuvin 327 in resin were used (0.00, 0.05, 0.10, and 0.15 percent (w/w)), and cure depth experiments were performed. To investigate the effects of different concentrations of Tinuvin 327 on complex 3D microstructure fabrication, several microstructures with overhanging features such as a fan and spring were fabricated.

Results showed that higher concentrations of Tinuvin 327 reduced penetration depths and thus cure depths. For the resin with 0.15 percent (w/w) of the Tinuvin 327, a cure depth of ∼30 μm was achieved as compared to ∼200 μm without the light absorber. The four resin solutions were used to fabricate complex 3D microstructures, and different concentrations of Tinuvin 327 at a given irradiance and exposure energy were required for successful fabrication depending on the geometry of the micro‐part (concentrations of 0.05 and 0.1 percent (w/w) provided the most accurate builds for the fan and spring, respectively).

Although two different concentrations of light absorber in solution were required to demonstrate successful fabrication for two different micro‐part geometries (a fan and spring), the experiments were performed using a single irradiance and exposure energy. A single solution with the light absorber could have possibly been used to fabricate these micro‐parts by varying irradiance and/or exposure energy, although the effects of varying these parameters on geometric accuracy, mechanical strength, overall manufacturing time, and other variables were not explored.

This work systematically investigated 3D microstructure fabrication using different concentrations of a light absorber in solution, and demonstrated that different light absorption characteristics were required for different down‐facing micro‐features.

To establish an accurate and sensitive method to characterize the moisture content of a particular environment.

This paper proposes a relatively simple humidity sensor design consisting of electrodes on a suitable substrate coated with a polyimide material. The changes in relative humidity are denoted by a corresponding change in the polyimide material's electrical resistance profile. The design proposed in this work can be microfabricated and integrated with electronic circuitry. This sensor can be fabricated on alumina or silicon substrates. The electrode material can be made up of nickel, gold or aluminum and the thickness of the electrodes ranges typically between 0.2 and 0.3 μm. The sensor consists of an active sensing layer on top of a set of electrodes. The design of the electrodes can be configured for both resistive and capacitive sensing.

The polyimide material's ohmic resistance changes significantly with humidity variations. Changes in resistance as large as 4‐6 orders of magnitude are attainable over the entire operational humidity range.

As the sensitivity varies non‐linearly with the humidity, the measurement has to be carried out over a very wide range in order to calibrate the sensor. The sensitivity and output range of the sensor can be easily controlled by changing the electrode spacing or geometry.

The control of humidity is important in many applications ranging from bio‐medical to space exploration.

A simple, easy to fabricate and measure, and low cost resistive‐type humidity sensor was developed. The realized sensor is suitable for integrating with microfabrication. Hence, multiple sensors of varying sensitivities and output ranges could be integrated on the same chip. Over the last few years, newly emerging micro‐electro‐mechanical‐systems technology and micro‐fabrication techniques have gained popularity and importance in the miniaturization of a variety of sensors and actuators.

The purpose of this research is to develop an automatic optical inspection system for thin film transistor (TFT) liquid crystal display (LCD).

A new algorithm that accounts for the closing, opening, etching, dilating, and genetic method is used. It helps to calculate the location and rotation angle for transistor patterns precisely and quickly. The system can adjust inspection platform parameters according to viewed performance. The parameter adaptation occurs in parallel with running the genetic algorithm and imaging processing methods. The proposed method is compared with the algorithms that use artificial parameter sets.

This system ensures high quality in an LCD production line. This multipurpose image‐based measurement method uses unsophisticated and economical equipment, and it also detects defects in the micro‐fabrication process.

The experiment's results show that the proposed method offers advantages over other competing methods.

X‐ray lithography is an important technique in micro fabrication used to obtain structures and devices with a high aspect ratio. The X‐ray exposure takes place in a system composed of a mask and a photoresist deposited on a substrate (with a gap between mask and resist). Predictions of the temperature distribution in three dimensions in the different layers (mask, gap, photoresist and substrate) and of the potential temperature rise are essential for determining the effect of high flux X‐ray exposure on distortions in the photoresist due to thermal expansion. In this study, we develop a three‐dimensional numerical method for obtaining the temperature profile in an X‐ray irradiation process by using a hybrid finite element‐finite difference scheme for solving three‐dimensional parabolic equations on thin layers. A domain decomposition algorithm is then obtained based on a parallel Gaussian elimination for solving block tridiagonal linear systems. The method is illustrated by a numerical method.

One of the key components of the micro-sensors is MEMS micro-hotplate. The purpose of this paper is to introduce a platinum micro-hotplate with the proper geometry using the analytical model based on the heat transfer analysis to improve both heating efficiency and time constant.

This analytical model exhibits that suitable design for the micro-hotplate can be obtained by the appropriate selection of square heater (LH) and tether width (WTe). Based on this model and requirements of routine sample loading, the size of LH and WTe are chosen 200 and 15 μm, respectively. In addition, a simple micro-fabrication process is adopted to form the suspended micro-heater using bulk micromachining technology.

The experimental results show that the heating efficiency and heating and cooling time constants are 21.27 K/mW and 2.5 ms and 2.1 ms, respectively, for the temperature variation from 300 to 400 K in the fabricated micro-hotplates which are in closed agreement with the results obtained from the analytical model with errors within 5 per cent.

Our design based on the analytical model achieves a combination of fast time constant and high heating efficiency that are comparable or superior to the previously published platinum micro-hotplate.

X‐ray irradiation of photoresists, such as polymethylmethacrylate (PMMA), on a silicon substrate is an important technique in micro fabrication used to obtain structures and devices with a high aspect ratio. The process is composed of a mask and a photoresist deposited on a substrate (with a gap between mask and resist). Predictions of the temperature distribution in three dimensions in the different layers (mask, gap, photoresist and substrate) and of the potential temperature rise are essential for determining the effect of high flux X‐ray exposure on distortions in the photoresist due to thermal expansion. In this study, we develop a numerical method for obtaining the steady state temperature profile in an X‐ray irradiation process by using a preconditioned Richardson method for the Poisson equation in the micro‐scale. A domain decomposition algorithm is then obtained based on the parallel “divide and conquer” procedure for tridiagonal linear systems. Numerical results show that such a method is efficient.