Table of contents

Printing technologies have undergone signficant development because they are an enabler in science and engineering research; they also have significant practical applications in manufacturing. Micro- and nano-printing techniques have found a number of applications in electronics, biotechnology, and material synthesis/patterning. In this review, we look at the important printing methods, including high precision traditional printing methods as well as recently emerging techniques. We also discuss the materials that are printable by these technologies, the challenges for future development, and the applications of micro- and nano-printing.

A novel concept of single-nozzle micro-dispensing device with multiple pressurizing chambers is proposed for high-throughput drug screening applications such as arraying new drug candidates with sub-nanoliter volume. The theoretical study with a simplified electrical circuit model of the fluidic system shows that the proposed model is effective to sustain jetting stability at high frequency due to an increase in the natural frequency of the fluidic system and high attenuation of the negative pressure wave in the fluidic system. The fabricated device was able to form uniform droplets at up to 7 kHz having 115 pL (1.15 × 10⁻¹⁰ L) in volume and 1.8 m s⁻¹ ∼ 2.5 m s⁻¹ in velocity.

In this study, we fabricated and fully characterized a new type of polystyrene (PS) cell-culture platform containing nanoengineered surfaces (NES), referred to as a nano Petri dish, which can be used at the transition stage of basic cell–NES interaction studies for clinical applications. Nano-injection molding in this study was used for the mass production of the nano Petri dish having nanopore arrays. The effects of processing parameters of the injection molding on the replication quality of the nanopore arrays were quantitatively evaluated by means of design of experiments based on the Taguchi method. This allowed efficient and reliable cell culture studies by providing large numbers of the same dishes, in addition to removing the fixation step of the NES plates inside the cell-culture container. Physical, chemical and mechanical properties of the NES, as well as cell behavior including attachment and proliferation of human osteosarcoma MG-63 cells on the NES, were then characterized, with and without the oxygen plasma surface treatment.

We report on the development of an electrospray (ES) microthruster that, by emitting fast nanodroplets, covers a wide range of specific impulse and thrust at high (>50%) propulsion efficiency. To achieve a useful thrust, many ES microthrusters must operate in parallel (multiplexing). The multiplexed electrospray microthruster (MES) is packaged in an alumina case that can operate at voltages up to ΔV = 7.56 kV and a reservoir pressure up to 5 bar. We compared nozzle arrays with 7, 37 and 91 capillaries (ID/OD = 10/30 µm). To ensure uniform flow through the various emitters, the hydraulic resistance was increased by filling the capillaries with 2.01 µm beads. The MES devices sprayed the ionic liquid ethylammonium nitrate. The 37-MES device covered a 2.6-fold range of specific impulse reaching 1870 s, and a 4.2-fold range of thrust up to 31.1 µN. The 91-MES device reached higher thrust, but it covered a narrower range. All devices operated stably for hours with modest current fluctuations. The beam cleared the electrodes, with no signs of erosion. The developed microthruster has already reached performances suitable for fine attitude control of microsatellites. Further scaling up by one order of magnitude would enable orbit change and station keeping for small satellites.

In this paper, we develop closed expressions for the equivalent bending and shear stiffness of beams with regular square perforations, and apply them to the problem of determining the resonance frequencies of slender, regularly perforated clamped–clamped beams, which are of interest in the development of MEMS resonant devices. We prove that, depending on the perforation size, the Euler–Bernoulli equation or the more complex shear equation needs to be used to obtain accurate values for these frequencies. Extensive finite element method simulations are used to validate the proposed model over the full practical range of possible hole sizes. An experimental verification of the model is also presented.

This paper investigates the enhanced sensitivity to external perturbations through mode localization in a coupled resonant MEMS transducer device. An energy-based framework is developed to analytically study energy localization in the MEMS device by using a novel, electrostatically-induced stiffness perturbation. Specifically, we analyze the mode localization associated with eigenvalue veering phenomenon, resulting from a symmetry-breaking perturbation in a coupled two-resonators MEMS device. The measured mode shape sensitivities are compared with predictions made by both a simplified analytical model and a more detailed Simulink model. The mode shape sensitivity to perturbations is shown to be an order of magnitude higher than that of resonant frequency shifting. The sensitivity can be further increased by decreasing the coupling strength between the two resonators, but with a reduced dynamic range of the external perturbations.

We demonstrate a scalable and repeatable method to fabricate micro/nanotubes. Mask-based diffraction lithography was modeled, and the effects of key parameters including the wavelength of the illuminant light, the thickness of the photoresist, the diameter of the photomask pattern and the exposure dose during the process were simulated. Analysis of the results indicates that the optical intensity distributions in the photoresist form separated regions, which can be used to fabricate micro/nanotubes. Experiments were then carried out, and we achieved the production of silicon microtubes and tube-in-tube arrays. It can be found that the outer diameter of the microtubes decreases while the inner diameter increases with the increment of exposure time, consistent with the simulation results. Thus, the optical model is suitable for explaining experimental phenomena, guiding experiments and optimizing the fabrication process. The obtained silicon microtubes exhibit fine hydrophobic properties and provide a good matrix for integrating active nanomaterials, which can provide great potential in their application to energy storage devices, solar cells, sensors and catalysts.

During the demoulding stage of the hot embossing process, the force required to separate a polymer part from the mould should be minimized to avoid the generation of structural defects for the produced micro structures. However, the demoulding force is dependent on a number of process factors, which include the material properties, the demoulding temperature, the polymer pressure history and the design of the mould structures. In particular, these factors affect the chemical, physical and mechanical interactions between a polymer and the replication master during demoulding. The focus of the reported research is on the development and validation of an analytical model that takes into account the adhesion, friction and deformation phenomena to predict the required demoulding force in hot embossing under different processing conditions. The results indicate that the model predictions agree well with the experimental data obtained and confirm that the design of the mould affects the resulting demoulding force. In addition, the applied embossing load was observed to have a significant effect on demoulding. More specifically, the increase in pressure within the polymer raises the adhesion force while it also reduces the friction force due to the decrease in the thermal stress.

This paper presents a self-aligning ink by integrating an inkjet printing technique and heterostructures to fabricate a black matrix with a micrometer-scale tunable thickness. The black matrix is a grid-like structure used in color filters. Traditionally, a black matrix has been fabricated using photolithography techniques, the disadvantages of which are high material consumption, less fabrication flexibility, complex processing procedures, and high chemical pollution. Inkjet printing technology has garnered attention because of its low material costs, high fabrication flexibility, and reduced processing procedures and pollution. In this study, a fabricating process combining an inkjet printing technique with heterostructures to form stripe-arranged and delta-arranged thickness-tunable black matrices has been demonstrated. The deformation and self-aligning process of ink droplet impingement onto gutters are driven by designed heterogeneous surface properties. The minimum track width attained is 10 µm, which is competitive for color filter resolutions for thin-film transistor liquid crystal displays. The developed technology surmounts the bottlenecks of inkjet printing resolution, and saves more than 75% black material than modern photolithography.

A miniaturized two-dimensional forward optical scanner with a monolithically integrated glass microlens was developed for microendoscopic imaging applications. The fabricated device measures 2.26 × 1.97 × 0.62 mm³ in size and a through-silicon microlens with a diameter of 400 µm and numerical aperture of 0.37 has been successfully integrated within the silicon layer. An XY stage structure with lens shuttle and comb actuators was designed, and proprietary glass isolation blocks were utilized in mechanical and electric isolation of X- and Y-axis actuators. Resonant frequencies of the stage in X and Y directions were 3.238 and 2.198 kHz and quality factors were 168 and 69.1, respectively, at atmospheric pressure. Optical scanning test has been performed and scan angles of ±4.7° and ±4.9° were achieved for X and Y directions, respectively.

An intensive, energy-based analysis of the thermal reflow of thermoplastic polymer structures is presented. Poly (methyl methacrylate) (PMMA) was patterned by grayscale electron beam lithography. The obtained rectangular, micron-scale structures were transformed into lens-like structures by thermal reflow near the glass transition temperature of the original PMMA. Representative parameters obtained from these reflow experiments were used to model the reflow process by using a new, energy-based, finite element, soapfilm method using the free software Surface Evolver. The time-, temperature- and molecular-weight-dependent geometry evolution of the PMMA structures could be described by an apparent contact-angle-evolution time constant and a shape-evolution time constant. The developed model allows the prediction of intermediate geometries during the reflow process occurring between the initial and the final energy optimal geometry. The proposed model is independent from the explicit knowledge of material-specific parameters such as viscosity or glass transition temperature. Extensive experimental data for PMMA reflow is provided. Simulation examples are given for a contact-angle-dominated reflow which demonstrate a good agreement between model and experiment.

Pure polyurethane and nanocomposite carbon black (CB) polyurethane solutions were deposited by spin-coating on a silicon substrate using gold as the adhesion layer and electrode. Different test structures were achieved for electrical and mechanical characterizations. The incorporation of CB nanoparticles in the polyurethane matrix has a significant influence on the dielectric permittivity of the material with an increase of about one third of its value. The Young's modulus of PU and nanocomposite PU films was determined by different characterization methods. Nanoindentation experiments have pointed out a Young's modulus gradient through the film thickness. By performing mechanical tests (tensile, bulge, point deflection) on freestanding films, an average Young's modulus value of about 30 MPa was found as well as a residual stress value of about 0.4 MPa. However, no influence of the presence of the nanoparticles was found. Finally, several MEMS actuators were realized and characterized. At their fundamental resonance frequency, the actuation of the nanocomposite membranes is more efficient than that of pure polyurethane. However, the time constant of the material seems to provide a major barrier for the development of high-frequency PU-based micro-actuators.

In this paper, the characterization of sliders for efficient force generation of an electrostatically controlled linear actuator (ECLIA) is investigated. The ECLIA consists of a piezoactuator (PZT), driving and holding electrodes, multiple sliders and a guide structure. The stepping motion of the sliders is driven by the PZT actuator via an electrostatic clutch mechanism. Thus, multiple sliders can achieve parallel, independent, precise motion, and a large stroke. Previous studies have indicated that the Si bulk slider and Si electrode created an air gap owing to the deformation of the Si electrode. Thus, the Si slider generated a low pushing force. In this study, we propose a fishbone structure mounted on a flexible slider to enhance the pushing force of the slider. The flexible slider, that can deform and fit into the Si electrode to reduce the air gap, results in highly efficient electrostatic-force generation. The fishbone structure improves the longitudinal stiffness of the flexible slider for high pushing-force generation. The results show that the pushing force created by the fishbone slider was three times greater than that of the conventional Si slider. The fishbone and flexible sliders exhibited a high performance for the ECLIA.

Measurement and modeling of gas flows in microelectromechanical systems (MEMS) scale channels are relevant to the fundamentals of rarefied gas dynamics (RGD) and the practical design of MEMS-based flow systems and micropumps. We describe techniques for building robust, leak-free, rectangular microchannels which are relevant to micro- and nanofluidic devices, while the channels themselves are useful for fundamental RGD studies. For the first time, we report the isothermal steady flow of helium (He) gas through these channels from the continuum to the free-molecular regime in the unprecedented Knudsen range of 0.03–1000. On the high end, our value is 20-fold larger than values previously reported by Ewart et al (2007 J. Fluid Mech.584 337–56). We accomplished this through a dual-tank accumulation technique which enabled the monitoring of very low flow rates, below 10⁻¹⁴ kg s⁻¹. The devices were prebaked under vacuum for 24 h at 100 °C in order to reduce outgassing and attain high Kn. We devised fabrication methods for controlled-depth micro-gap channels using silicon for both channel ceiling and floor, thereby allowing direct comparisons to models which utilize this simplifying assumption. We evaluated the results against a closed-form expression that accurately reproduces the continuum, slip, transition, and free-molecular regimes developed partly by using the direct simulation Monte Carlo method. The observed data were in good agreement with the expression. For Kn > ∼100, we observed minor deviations between modeled and experimental flow values. Our fabrication processes and experimental data are useful to fundamental RGD studies and future MEMS microflow devices with respect to extremely low-flow measurements, model validation, and predicting optimal designs.

Dual-mode flexible ZnO/polyimide surface acoustic wave (SAW)-based ultraviolet (UV) light sensors were fabricated and their performance was investigated. UV light sensing measurements showed that the responses of the dual wave modes of the sensors increase with the increase of light intensity and the frequency changes linearly with the change of light intensity. Under a 4.5 mW cm⁻² UV light illumination, the resonant frequency of the Rayleigh wave decreased up to ∼43 kHz, while that of the Lamb wave was approximately 76 kHz. The UV light sensitivities for the two resonant modes are 111.3 and 55.8 ppm (mW cm⁻²)^–1, respectively. The resonant frequency, phase angle and amplitude of the two resonant modes exhibited a good repeatability in responding to cyclic change of the UV light, and an excellent stability up to a long duration of UV light exposure. The dual-mode flexible SAW resonators are simple in structure, more accurate in detection, and can be fabricated at low cost are, therefore, very promising for application in flexible sensors and electronics.

A tungsten-carbide (W-C) superconductor/normal metal/superconductor (SNS) Josephson junction has been fabricated using focused-ion-beam chemical vapour deposition (FIB-CVD). Under certain process conditions, the component ratio has been tuned from W: C: Ga = 26%: 66%: 8% in the superconducting wires to W: C: Ga = 14%: 79%: 7% in the metallic junction. The critical current density at 2.5 K in the SNS Josephson junction is 1/3 of that in W-C superconducting nanowire. Also, a Fraunhofer-like oscillation of critical current in the junction with four periods is observed. FIB-CVD opens avenues for novel functional superconducting nanodevices.

A control system using a low-drift power-feedback signal was implemented applying thermal waves, giving a sensor output independent of resistance drift and thermo-electric offset voltages on interface wires. Kelvin-contact sensing and power control is used on heater resistors, thereby inhibiting the influence of heater resistance drift. The thermal waves are detected with a sensing resistor using a lock-in amplifier and are mutually cancel­led by a thermal-wave balancing controller. Offset due to thermal gradient across the chip and resistor drift are eliminated by the lock-in amplifier and power controller, and therefore do not influence the sensor output signal. A microchannel thermal-wave balancing flow sensor with integrated Al resistors has successfully been fabricated. The thermal flow sensor is capable of measuring water flow rates with nl ⋅ min⁻¹ precision, up to about 500 nl ⋅ min⁻¹ full scale. Measurement results are in good agreement with a dynamic model of the flow sensor. Drift measurements show the sensor output signal to be compensated for resistance drift and thermal gradient across the chip.

Nature's functional surfaces are typically hierarchical multiscale structures. There are several techniques for producing such artificial structures on polymers but their mass production is not straightforward. We present here a simple and versatile method for manufacturing hierarchical multiscale polymer surface patterns. The microroughening technique permits the single-step production of multilevel three-dimensional surface architectures in a mechanically durable nickel mold. The molding technique is suitable for area-controlled fabrication of structures with various geometrical shapes on smooth and curved surfaces. The mold structures were transferred to polypropylene surfaces by means of injection molding. The fabricated surface structures were characterized by using a filtered power spectral density method which facilitated a quantitative study of the roughness distributions at different length scales of structure periodicities. Analysis showed that the microroughening technique is an appropriate tool for controlled production of surface roughness at a micro-nanometer scale. Roughness distribution values can be used for predicting surface structure-related properties such as wetting, and the distributions can also be simulated without an experimental preparation process. The work presents a suitable approach for mass production of hierarchical polymer surfaces at different length scales and provides a new route for designing surface structures with tunable wetting properties.

We report a vertically-aligned carbon nanotube (CNT) forest on polydimethylsiloxane (PDMS) sheet as a novel widely stretchable and bendable anti-wetting super-lyophobic surface for naturally oxidized gallium-based liquid metals. The vertically-aligned CNT has inherent chemical inertness and a hierarchical texture combining micro/nanoscale roughness; these two characters render the developed sheet as a super-lyophobic substrate against gallium-based liquid metals. The vertically-aligned CNT forest was first grown on Si substrate and then transferred onto a PDMS sheet by imprinting. It was found that the transferred CNT on the PDMS sheet maintained its vertically-aligned nature as well as hierarchical micro/nano surface morphology. It was found that the static contact angles of the gallium-based liquid metal droplet on the CNT on Si and on the CNT on PDMS were both greater than 155° and the contact angle hysteresis on the CNT on Si was 4° and that on the transferred CNT on PDMS was 19°. These measurement results showed that the surface retains a super-lyophobic property before and after the CNT transfer onto PDMS. We tested the CNT on PDMS sheet for its mechanical flexibility using stretching (50% and 100%) and bending (curvature of 0.1 and 0.4 mm⁻¹). We carried out a bouncing test and a rolling test on the stretched/bent CNT on the PDMS sheet and the results confirmed that the flexible sheet maintains anti-wetting characteristics under bending or stretching conditions.

Thin film devices can be of significance for manufacturing, energy conversion systems, solid state electronics, wireless applications, etc. However, these thin film sensors/devices are normally fabricated on rigid silicon substrates, thus neither flexible nor transferrable for engineering applications. This paper reports an innovative approach to transfer polyimide (PI) embedded thin film devices, which were fabricated on glass, to thin metal foils. Thin film thermocouples (TFTCs) were fabricated on a thin PI film, which was spin coated and cured on a glass substrate. Another layer of PI film was then spin coated again on TFTC/PI and cured to obtain the embedded TFTCs. Assisted by oxygen plasma surface coarsening of the PI film on the glass substrate, the PI embedded TFTC was successfully transferred from the glass substrate to a flexible copper foil. To demonstrate the functionality of the flexible embedded thin film sensors, they were transferred to the sonotrode tip of an ultrasonic metal welding machine for in situ process monitoring. The dynamic temperatures near the sonotrode tip were effectively measured under various ultrasonic vibration amplitudes. This technique of transferring polymer embedded electronic devices onto metal foils yield great potentials for numerous engineering applications.

Ultraviolet-assisted three-dimensional (3D) printing (UV-3DP) was used to manufacture photopolymer-based microdevices with 3D self-supported and freeform features. The UV-3DP technique consists of the robotized deposition of extruded filaments, which are rapidly photopolymerized under UV illumination during the deposition process. This paper systematically studies the processing parameters of the UV-3DP technique using two photo-curable polymers and their associated nanocomposite materials. The main processing parameters including materials' rheological behavior, deposition speed and extrusion pressure, and UV illumination conditions were thoroughly investigated. A processing map was then defined in order to help choosing the proper parameters for the UV-3DP of microstructures with various geometries. Compared to self-supported features, the accurate fabrication of 3D freeform structures was found to take place in a narrower processing region since a higher rigidity of the extruded filament was required for structural stability. Finally, various 3D self-supported and freeform microstructures with high potential in micro electromechanical systems, micro-systems and organic electronics were fabricated to show the capability of the technique.

A low-cost filler (salt) water-dissolved method is developed to produce large-area and flexible super-hydrophobic surfaces by using poly(dimethylsiloxane) (PDMS) material. Five levels of salt grain sizes are used to examine the filler size effect on fabricating the super-hydrophobic surfaces and on the hydrophobic mechanism involved. The results show that the surfaces fabricated using grain sizes of 53–74 and 74–104 µm exhibit the lotus effect (cell adhesion (CA) > 150° and self-adhesion (SA) < 10°); whereas those using grain sizes of 0–25 µm and above 104 µm reveal the petal effect (CA > 150° and high adhesion even upside-down). The super-hydrophobic characteristic is achieved mainly by the large micro rib-like structures, small micro rock-like bumps, and textures on the bump due to the fillers.

This paper describes the development of a novel technology that can form a dense and complex pattern on a polymer tube without thermal damage. We have developed an etching mask and equipment capable of processing the tubular material. We named this technology cylindrical RIE (reactive ion etching). In order to evaluate the fundamental processing characteristics of this technology, etching rate, side etching ratio and etching uniformities along the tube axis and circumferential directions are evaluated. As a result, a vertical wall caused by anisotropic etching could be observed, and the average etching rate was 1.0 µm min⁻¹ and the average side etching ratio was 0.027. The maximum differences between etching rate along the axis and circumferential directions were 0.25 and 0.12 µm min⁻¹, respectively. The cross-section of the etched through-groove (slit) processed in a PP (polypropylene) tube having wall thickness of 200 µm was evaluated. By the bowing phenomenon, pattern width decreased most at the middle of the thickness of the tube wall, and average width errors at the middle of the thickness was 22.4 µm. To demonstrate the usefulness of the cylindrical RIE, a stent made of PP tube was fabricated. It was possible to fabricate a stent with an outer diameter of 4.4 mm, length of 19 mm, main strut width of 300 µm, and connecting strut width of 80 µm.

The production of nanostructured plastic items by injection molding with ridges down to 400 nm in width, which is the smallest line width replicated from nanostructured steel shims, is presented. Here we detail a micro-fabrication method where electron beam lithography, nano-imprint lithography and ion beam etching are combined to nanostructure the planar surface of a steel wafer. Injection molded plastic parts with enhanced surface properties, like anti-reflective, superhydrophobic and structural colors can be achieved by micro- and nanostructuring the surface of the steel molds. We investigate the minimum line width that can be realized by our fabrication method and the influence of etching angle on the structure profile during the ion beam etching process. Trenches down to 400 nm in width have been successfully fabricated into a 316 type electro-polished steel wafer. Afterward a plastic replica has been produced by injection molding with good structure transfer fidelity. Thus we have demonstrated that by utilizing well-established fabrication techniques, nanostructured steel shims that are used in injection molding, a technique that allows low cost mass fabrication of plastic items, are produced.

Mechanically flexible interconnects (MFIs) with highly scalable pitch (from 150 to 50 µm) and large vertical gap (65 µm) are reported for the first time in this paper. The wafer-level batch fabrication of the reported MFIs is enabled by photolithography on a highly non-uniform surface (65 µm high sacrificial domes) covered with a spray-coated photoresist. Based on finite element method simulations and experimental data, the mechanical compliance and resistance of the fabricated MFIs are reported.

A device including a pair of top electrodes and a local gate in the bottom of an SU-8 trench was fabricated on a glass substrate for dielectrophoresis assembly and electrical characterization of suspended nanomaterials. The three terminals were made of gold electrodes and electrically isolated from each other by an air gap. Compared to the widely used global back-gate silicon device, the parasitic capacitance between the three terminals was significantly reduced and an individual gate was assigned to each device. In addition, the spacing from the bottom-gate to either the source or drain was larger than twice the source-drain gap, which guaranteed that the electric field between the source and drain in the dielectrophoresis assembly was not distinguished by the bottom-gate. To prove the feasibility and versatility of the device, a suspended carbon nanotube and graphene film were assembled by dielectrophoresis and characterized successfully. Accordingly, the proposed device holds promise for the electrical characterization of suspended nanomaterials, especially in a high frequency resonator or transistor configuration.

Ever since the appearance of nanomaterials and nanotechnologies, they have been used in almost every type of microbattery except for nuclear ones. Here we present a radioisotope betavoltaic (BV) microbattery based on a single-walled carbon nanotube (SWCNT) film that acts as a carrier separator. SWCNT film also provides a shortcut for carrier transportation. The energy conversion efficiency of a BV microbattery can reach up to 0.15% after the subtraction of the energy loss of beta particles in air and SWCNT film, proving that the SWCNT film-silicon heterojunction presents a promising configuration suitable for use in radioisotope BV microbatteries. Tracing the particle route, we achieved a charge collection rate of 59.9%, indicating that our device could potentially achieve higher performance. Primary strategies to improve the performance of the BV microbattery are discussed.

Multilayer soft lithography has become a powerful tool in analytical chemistry, biochemistry, material and life sciences, and medical research. Complex fluidic micro-circuits require reliable components that integrate easily into microchips. We introduce two novel approaches to master mold fabrication for constructing in-line micro-valves using SU-8. Our fabrication techniques enable robust and versatile integration of many lab-on-a-chip functions including filters, mixers, pumps, stream focusing and cell-culture chambers, with in-line valves. SU-8 created more robust valve master molds than the conventional positive photoresists used in multilayer soft lithography, but maintained the advantages of biocompatibility and rapid prototyping. As an example, we used valve master molds made of SU-8 to fabricate PDMS chips capable of precisely controlling beads or cells in solution.

Here we present facile microfabrication processes, referred to as print-to-pattern dry film photoresist (DFP) lithography, that utilize the combined advantages of wax printing and DFP to produce micropatterned substrates with high resolution over a large surface area in a non-cleanroom setting. The print-to-pattern methods can be performed in an out-of-cleanroom environment making microfabrication much more accessible to minimally equipped laboratories. Two different approaches employing either wax photomasks or wax etchmasks from a solid ink desktop printer have been demonstrated that allow the DFP to be processed in a negative tone or positive tone fashion, respectively, with resolutions of 100 µm. The effect of wax melting on resolution and as a bonding material was also characterized. In addition, solid ink printers have the capacity to pattern large areas with high resolution, which was demonstrated by stacking DFP layers in a 50 mm × 50 mm woven pattern with 1 mm features. By using an office printer to generate the masking patterns, the mask designs can be easily altered in a graphic user interface to enable rapid prototyping.