Showing papers in "Journal of Micromechanics and Microengineering in 2001"

A review of focused ion beam applications in microsystem technology

Abstract: In this paper the possibilities of focused ion beam (FIB) applications in microsystem technology are reviewed. After an introduction to the technology and the operating principles of FIB, two classes of applications are described. First the subject of FIB for microsystem technology inspection, metrology and failure analysis is outlined. A procedure for cross sectioning on samples is presented, as well as some examples of how this technique can be applied to study processing results. The second part of the paper is on the use of FIB as a tool for maskless micromachining. Both subtractive (etching) and additive (deposition) techniques are discussed, as well as the combination of FIB implantation of silicon with subsequent wet etching. We will show the possibility to fabricate three-dimensional structures on a micrometre scale, and give examples of recent realizations thereof.

Mixing characteristics of T-type microfluidic mixers

Abstract: Computational fluid dynamics simulations are used to study the mixing characteristics of a microscale mixer for gaseous flow as a function of various operating and design parameters. The device is based on a T configuration and gases of different viscosities are employed. Simulations show that the mixing length increases with the fluid speed and is also influenced by the mixer aspect ratio. Altering the angle between the inlet channels does not significantly affect the mixing performance, whilst throttling the fluid considerably decreases the mixing length. The results are compared with Fourier number predictions and it is demonstrated that these can provide useful limits for a preliminary design.

Low temperature full wafer adhesive bonding

Abstract: We have systematically investigated the influence of different bonding parameters on void formation in a low-temperature adhesive bonding process. As a result of these studies we present guidelines ...

A fast prototyping process for fabrication of microfluidic systems on soda-lime glass

Abstract: This paper describes a fast, low-cost but reliable process for the fabrication of microfluidic systems on soda-lime glass substrates. Instead of using an expensive metal or polisilicon/nitride layer as an etch mask, a thin layer of AZ 4620 positive photoresist (PR) is used for buffered oxide etching (BOE) of soda-lime glass. A novel two-step baking process prolongs the survival time of the PR mask in the etchant, which avoids serious peeling problems of the PR. A new process to remove precipitated particles generated during the etching process is also reported in which the glass substrate is dipped into a 1 M hydrochloride solution. A microfluidic channel with a depth of 35.95±0.39 µm is formed after 40 min BOE in an ultrasonic bath. The resulting channel has a smooth profile with a surface roughness of less than 45.95±7.96 A. Glass chips with microfluidic channels are then bonded at 580 °C for 20 min to seal the channel while a slight pressure is applied. A new bonding process has been developed such that the whole process can be finished within 10 h. To our knowledge, this is the shortest processing time that has ever been reported. In the present study, an innovative microfluidic device, a `micro flow-through sampling chip', has been demonstrated using the fabrication method. Successful sampling and separation of Cy5-labelled bovine serum albumin (BSA) and anti-BSA has been achieved. This simple fabrication process is suitable for fast prototyping and mass production of microfluidic systems.

Microfluidic systems with on-line UV detection fabricated in photodefinable epoxy

Abstract: This paper describes a method for fabricating microfluidic devices in a photodefinable epoxy (SU-8). This technique is compatible with, and complementary to, conventional fabrication techniques. It allows microstructures formed in SU-8 to be bonded to produce sealed microfluidic channels. A micromixer fabricated entirely in SU-8, using this technique, for performing liquid-phase reactions is shown to be suitable for visible spectroscopy. This fabrication method also allows the incorporation of materials that are often difficult to integrate. By fabricating hybrid devices that incorporate quartz windows, we demonstrate that these devices are compatible with organic solvents and that in situ ultraviolet detection in a microfluidic system is possible.

Polymerization optimization of SU-8 photoresist and its applications in microfluidic systems and MEMS

Abstract: In this paper, SU-8 EPON-based photoresist (PR) polymerization optimization and its possible microfluidic and MEMS applications are reported. First, the optimization results of SU-8 under UV lithography are reported. The parameters which could have an influence on the lithography quality were chosen and optimized by a three-level, L9 orthogonal array of the Taguchi method. By optimization, the optimal parameter range and the weighted per cent of a parameter on the final results were determined. For SU-8-5 and SU-8-50, many microstructures with thicknesses of more than 100 and 500 µm and aspect ratios of more than 20 and 50 were obtained with high resolution. The optimization results show that the prebake time plays the key role in the quality, which is different from the previously published results. With the optimization results obtained, some possible applications of SU-8 were developed and demonstrated. These applications included using SU-8 as a structural material for a microfluidic system, as a micromold for electroplating, as a master for plastic hot-embossing, and even as a mask for some wet-etching processes.

Comprehensive thermal modelling and characterization of an electro-thermal-compliant microactuator

Abstract: A comprehensive thermal model for an electro-thermal-compliant (ETC) microactuator is presented in this paper. The model accounts for all modes of heat dissipation and the temperature dependence of thermophysical and heat transfer properties. The thermal modelling technique underlying the microactuator model is general and can be used for the virtual testing of any ETC device over a wide range of temperatures (300-1500 K). The influence of physical size and thermal boundary conditions at the anchors, where the device is connected to the substrate, on the behaviour of an ETC microactuator is studied by finite element simulations based on the comprehensive thermal model. Simulations show that the performance ratio of the microactuator increased by two orders of magnitude when the characteristic length of the device was increased by one order of magnitude from 0.22 to 2.2 mm. Restricting heat loss to the substrate via the device anchors increased the actuator stroke by 66% and its energy efficiency by 400%, on average, over the temperature range of 300-1500 K. An important observation made is that the size of the device and thermal boundary conditions at the device anchor primarily control the stroke, operating temperature and performance ratio of the microactuator for a given electrical conductivity.

Deep wet etching of fused silica glass for hollow capillary optical leaky waveguides in microfluidic devices

Abstract: We report on a technology for the fabrication of hollow capillary optical leaky waveguides in fused silica glass. The fabrication process is based on lithography, wet chemical etching and aligned direct bonding. We have developed a single-layer photoresist soft mask which allows for channel etch depths up to 33 µm in fused silica glass. To our knowledge, such etch depths have never been achieved before in fused silica glass with single-layer soft etch masks. Aligned direct glass-glass bonding is used for the first time to obtain channels with almost circular profiles with diameters between 16 and 66 µm. Capillary optical leaky waveguides embedded into microfluidic devices can be used, for example, for capillary electrophoresis and hyper Rayleigh scattering.

A novel micro-machining method for the fabrication of thick-film SU-8 embedded micro-channels

Abstract: In this paper, a novel method to realize embedded micro-channels is presented. The presented technology is based on a direct write technique using proton beams to pattern thick-film SU-8. This proton micro-machining method allows the production of high aspect ratio and complex three-dimensional micro-structures in polymers with aspect ratios of over 100 and 20 using poly(methylmethacrylate) (PMMA) and SU-8 respectively. As the SU-8 is used as a structural material, its mechanical properties have to be characterized. For a start, the Young's modulus of the proton beam exposed SU-8 is determined using a stylus-type load-deflection method. The second part of this paper describes the underlying theory and method used by the author to determine the Young's modulus of the proton beam exposed SU-8. Measurements of the SU-8 micro-structures show that the Young's modulus is dependent on the proton beam exposure dose. An exposure dose of 9.5 nC mm-2 results in an average Young's modulus value of 4.254 GPa.

Mathematical modeling of drop mixing in a slit-type microchannel

Abstract: Fast solute mixing can be achieved in a microchannel by rapid unidirectional displacement of a discrete liquid drop. The recirculation streamlines created within the liquid during the drop’s motion cause the solute to interlayer across the channel depth, provided the interlayer diffusion of the solute is small. Uniform interlayering appears when the drop is displaced by more than three drop lengths in a slit-type microchannel, thereby reducing the solute diffusion distances to a fraction of the channel depth. By fabricating the microchannel to a depth of less than 50 µm even large molecules with a low diffusivity ( D< 10 −8 cm 2 s −1 ) can be mixed in seconds. The above strategy is shown by modeling the mixing of solutes present in a drop moving in a slit-type microchannel.

Fluidic microsystems based on printed circuit board technology

Abstract: In this paper, fluidic microsystems based on an alternative fabricating technology are described. This technology mainly utilizes the manufacturing principles of printed circuit boards (PCBs). Minimal lateral structure dimensions of approximately 100 µm und vertical dimensions of some 10 µm are feasible. By introducing thin polymeric foils (6-13 µm in thickness) into a stack of PCBs, movable parts forming active or passive valves, pumps or sensors can be produced. The first results concerning several fluidic components based on PCB technology are presented.

Powder-blasting technology as an alternative tool for microfabrication of capillary electrophoresis chips with integrated conductivity sensors

Abstract: The fabrication and characterization of a microfluidic device for capillary electrophoresis applications is presented. The device consists of a glass chip which contains a single separation channel as well as an integrated conductivity detection cell. In contrast to most microfluidic glass devices the channels are not wet etched in HF but machined by the newly developed micro powder-blasting technique which allows the creation of microstructures below 100 µm, and additionally makes parallel hole machining at very low costs outside the cleanroom environment possible [1, 2]. The integration of the conductivity detector was achieved by leading two thin-film metal electrodes inside the separation channel. For rapid sample injection the chip is mounted inside an autosampler-based capillary electrophoresis platform. The detection electrodes for conductivity detection are read out by lock-in amplifier electronics. First measurements show the successful separation of various ions in the sub-millimeter range.

Fabrication of microchannels using polycarbonates as sacrificial materials

Abstract: The use of polycarbonates as thermally decomposable, sacrificial materials for the formation of microchannels is presented. Polycarbonates decompose in the temperature range of 200-300 °C. Two polycarbonates, polyethylene carbonate and polypropylene carbonate, have been used to fabricate microchannels in three different types of encapsulants: an inorganic glass (silicon dioxide), a thermoplastic polymer (Avatrel dielectric polymer) and a thermoset polymer (bisbenzoycyclobutene Cyclotene 3022-57). This paper presents the details of the fabrication process, a thermogravimetric analysis of the sacrificial materials, and the kinetic parameters for the decomposition process. The presence of oxygen or water was found to impact on the decomposition of the sacrificial material. This paper demonstrates the feasibility of forming buried air-cavities in a variety of encapsulants at a modest temperature, thus enabling the use of a wide range of dielectric materials with different thermal stabilities and properties.

Wafer-to-wafer bonding of nonplanarized MEMS surfaces using solder

Abstract: The fabrication and reliability of a solder wafer-to-wafer bonding process is discussed. Using a solder reflow process allows vacuum packaging to be accomplished with unplanarized complementary metal-oxide semiconductor (CMOS) surface topography. This capability enables standard CMOS processes, and integrated microelectromechanical systems devices to be packaged at the chip-level. Alloy variations give this process the ability to bond at lower temperatures than most alternatives. Factors affecting hermeticity, shorts, Q values, shifting cavity pressure, wafer saw cleanliness and corrosion resistance will be covered.

Advanced photoresist technologies for microsystems

Abstract: A growing interest in the development of high aspect ratio photoresists for micromachining microsystems (MST) products has resulted in the availability of a number of commercially available photoresist products. This paper describes in detail the applications of three such resists, namely EPON SU-8, Clariant AZ 4562 and the Shipley electroplated photoresist ED2100. Applications such as etch hard masks, micromoulds, severe topography coatings for metal interconnects and photoplastic mouldings are discussed, and novel examples are presented of where these resists are currently used in both telecomm and microfluidic markets. In particular, the versatility of the photoplastic negative resist EPON SU-8, which is used in a number of MST prototypes, is demonstrated. Future trends in resist technologies for MST are discussed.

Bubble-based micropump for electrically conducting liquids

Abstract: This paper describes a novel pumping device without mechanical moving parts based on the periodic generation and collapse of a single vapour bubble in a channel. The channel shape is such that it creates an asymmetry in the surface tension forces, which results in a pumping effect. The principle can be implemented over a broad range of channel sizes and repetition frequencies. For illustration purposes, a particular implementation is described here where the working fluid is a salt solution in water, the channel diameters are of the order of 1 mm and the repetition frequency is between 1-10 Hz. In these conditions, the device develops a head of a few centimetres of water with typical flow rates in the range of 100 µl per minute. It appears possible to increase both head and flow rate by adjusting geometrical parameters and operating conditions. A simple modification of the design would render the same principle also applicable to the pumping of non-conducting liquids.

Anisotropic etching of {100} and {110} planes in (100) silicon

Abstract: Anisotropic etching of (100) silicon using KOH with 45° alignment to the primary 110 wafer flat was investigated. It was shown that in KOH solution with isopropyl alcohol added, high KOH concentration and temperature caused the selection of {100} instead of {110} walls, allowing reliable fabrication of {100} walls with improved surface smoothness due to the isopropyl alcohol. TMAOH solutions with methanol and isopropyl alcohol were also found to produce both types of wall, with excellent surface smoothness for the {110} walls. A new maskless etching technique was developed for corner compensation of structures bounded by {110} walls.

Micromachined structures for thermal measurements of fluid and flow parameters

Abstract: In this paper thermal sensor-actuator structures are proposed that can be used to measure various fluid parameters such as thermal conductivity, flow velocity, heat capacity, kinematic viscosity and pressure. All structures are designed in such a way that they can be realized in the same fabrication process and therefore they can be easily combined in a single device. All structures are based on the principle of thermal measurements: resistive structures are used for both heating and temperature measurements. For accurate measurements the temperature coefficient of resistance (TCR) must be well known. Therefore, a special structure, which can be used for auto-calibration, was designed to measure the TCR. A first device containing structures for the combined measurement of flow velocity, thermal conductivity and TCR has been fabricated. Measurements show promising results.

Patterning, electroplating and removal of SU-8 moulds by excimer laser micromachining

Abstract: The ablation characteristics of the SU-8 photoresist (spun on Si wafers) under 248 KrF excimer pulsed laser radiation have been studied The variation of etch rate with fluence has been investigated in the range 005-301 J cm-2 The threshold fluence for ablation of SU-8 is measured to be about 005 J cm-2 The etch rate of SU-8 is found to be higher than that of polyimide (previously reported) under similar conditions We have investigated the effects of different prebake temperatures (90, 110, 120 and 200 °C) on ablation characteristics, which are found to be similar for all temperatures The effect of increasing the number of laser shots (from 10 to 10 000) has been examined at different fluences in order to understand the etch-rate variation near the `end of film' stage of ablation The results of our analysis using scanning electron microscopy, profilometry and optical microscopy reveal the very smooth morphology of the etched surfaces with no significant debris, no noticeable damage to underlying silicon and the gradual build-up of a carbonaceous film outside and around the etch pits We find SU-8 very suitable for excimer ablation lithography and have demonstrated this by patterning a gear structure in an SU-8 resist layer with an aspect ratio of 45 For the first time, we have shown that the laser micromachining technique has the potential to cleanly remove SU-8 after electroplating a microstructure with copper

Microfabrication of thermoelectric generators on flexible foil substrates as a power source for autonomous microsystems

Abstract: A flexible thermoelectric generator with overall dimensions of 16×20×0.05 mm has been fabricated using a unique low-cost procedure as part of our ongoing research efforts on developing economical and reliable energy sources for autonomous microsystems. The generator consists of a multiplicity of micro Sb-Bi thermocouple strips embedded in a 50 µm thick flexible epoxy film and is capable of generating a voltage of 0.25 V at a temperature difference of 30 K. Its fabrication involves only a few steps, such as foil lithography, electroplating, embedding and wet chemical etching. The exposure of aqueous photoresist on flexible foil substrates is carried out using a specially constructed mask aligner by Karl Suss GmbH. The thermocouple strips, with a cross section of 40×10 µm and a length of 20 mm, are electroplated galvanostatically from their associated acidic electrolytes into the patterned AZ 111XFS template on a 50 µm thick copper foil. After a top-over embedment of the electroplated structures with an epoxy film, the original copper substrate is removed completely by wet chemical etching, leaving the generator module to be embedded in the epoxy film. This process is proven to be cost-effective, easily manageable and highly reliable. It is now being applied to our current fabrication of more efficient thermoelectric generators based on n- and p-type Bi2Te3 compound materials.

Room-temperature wafer bonding of Si to LiNbO3, LiTaO3 and Gd3Ga5O12 by Ar-beam surface activation

Abstract: A room-temperature wafer bonding method using surface activation by Ar-beam sputter etching were applied to the bonding between dissimilar materials. LiNbO3, LiTaO3 and Gd3Ga5O12 wafers were successfully bonded to Si wafers without any heat treatment. This method is free from the various problems caused by the large thermal expansion mismatch between these materials during heat treatment in the conventional wafer bonding processes. The bond prepared by the Ar-beam treatment is so strong that fracture from inside the bulk materials is observed after the tensile test. The results of the bonding of Si wafers to both 128° Y-cut and Z-cut LiNbO3 wafers indicate that the influence of the crystal orientation on the bonding strength is negligible in this method. This method provides a very low damage bonding process for various material combinations regardless of any thermal expansion mismatch or crystal lattice mismatch.

Micromachined pre-focused M×N flow switches for continuous multi-sample injection

Abstract: In this paper we present a novel microfluidic chip capable of continuous multi-sample switching and injection for bio-analytical applications. The innovative device integrates two important microfluidic phenomena, including hydrodynamic focusing and valveless flow switching inside multi-ported microchannels. The multiple samples can be pre-focused to narrow streams and can then be continuously injected into desired outlet ports. In this study, a theoretical model based on the `flow-rate-ratio' method is first proposed to predict the performance of the microfluidic device. Then, a simple but reliable one-mask micromachining process is developed to fabricate the pre-focused M×N flow switch on a quartz substrate. The multi-sample switching and injection is then verified experimentally with the use of microscopic visualization of water sheath flows and dye-containing sample flows. The experimental data indicate that the multi-sample flows can be hydrodynamically pre-focused and then guided into the desired outlet ports precisely based on relative sheath and sample flow rates. The data predicted by the proposed theoretical model are highly consistent with the experimental results. It is also noted that the `pre-focusing' function added prior to multi-sample flow switching is crucial for precise sample injection. The novel microfluidic chip has great potential for high-throughput chemical analysis, cell fusion, fraction collection, fast sample mixing and many other applications in the field of micro-total-analysis systems.

Micro-to-macro fluidic interconnectors with an integrated polymer sealant

Abstract: This paper presents the design, fabrication and testing results of inserting a polymer sealant (Mylar) into a micro-to-macro fluidic interconnection. Two processes, discrete and integrated Mylar sealant, have been developed by means of post-fabrication after the mircofluidic components such as micro-channels and micro-chambers are constructed. The integrated process utilizes microfabrication techniques such that batch processing is feasible and the sealant dimensions can be precisely controlled. The discrete process takes advantage of easy and simple processing and is compatible with most microfluidic systems without any extra wafer-level micromachining process. In both processes, macroscale capillary tubes with a diameter of 320 µm have been successfully connected to microscale channels with the help of the Mylar. Both leakage and pull-out tests are conducted and successfully demonstrate the functionality of the interconnectors. The leakage test shows that no leakage is observed up to 190 kPa and the pull-out test proves 100% survival rate under a pulling force of 2 N. (Some figures in this article are in colour only in the electronic version)

An optimized micromachined convective accelerometer with no proof mass

Abstract: Miniaturization, low cost and high performance of accelerometers have been the topic of extensive research. A kind of convective micromachined accelerometer without proof mass is described in this paper. It consists of a microheater and two temperature sensors which measure the temperature difference between two sides of the microheater caused by the effect of acceleration on free convection. The optimization consideration is conducted before fabrication; some key factors, heater size and power, cavity size, distance between the heater and the sensor and the working medium, are considered. The test for the optimized device shows that the linearity error is smaller than 0.35% under tilt conditions of natural gravity and smaller than 2% under acceleration to 10 g (g = 9.81 m s-2). A sensitivity of 600 µV g-1 is measured for operating power of 87 mW, the response frequency is about 75 Hz and the corresponding noise equivalent acceleration is approximately 1 mg Hz-1/2 at 25 Hz. The dependence of the sensitivity on the heating power is a nearly linear function and the resolution increases with heating power increasing.

Soft and rigid two-level microfluidic networks for patterning surfaces

Abstract: We describe the microfabrication and use of elastomeric and rigid two-level microfluidic networks (?FNs), made of poly(dimethylsiloxane) (PDMS) or Si, for patterning surfaces. The first level corresponds to microchannels and the second to via holes through the ?FNs serving as filling and venting ports. ?FNs in PDMS are manufactured using a `sandwich' replication from a microfabricated four?inch mold structured with SU-8 photoresist, which is planarized by mechanical polishing. ?FNs in Si are microfabricated using deep reactive ion etching. Both types of ?FNs can be positioned onto a substrate, creating sealed microchannels, filled with different liquids, flushed, removed and reused. These two-level ?FNs allow us to access the ports from the rear, minimize interchannel crosstalk, and are economic of solutions. The channels are made wettable so that the liquids can flow spontaneously into the conduits, but stop at the venting ports. The sealing of the conduits usually requires that either the ?FN or the substrate be soft. A strategy for using hard two-level ?FNs, in Si, for patterning hard substrates is presented: despite voids in-between the ?FN and the substrate, a water-based solution can be guided by hydrophilic microchannels over a hydrophobic surface. Adjusting the wetting properties of the various surfaces is key to preventing undesired spreading of solutions. We illustrate our concepts by micromolding colored photocurable polymers on glass and patterning proteins as lines on a polystyrene surface.}

Ultra-fine machining tool/molds by LIGA technology

Abstract: Machining tools based on the excimer laser and x-ray lithography to make ultra-fine machining tool/molds are described in this paper. The lower high-aspect ratio resist molds are fabricated using the KrF excimer laser. The higher aspect-ratio resist molds are made using x-ray lithography. Both low and high aspect-ratio resist molds are then converted into metallic structures using electroforming. The NiCo/SiC microcomposite electroforming with low internal stress (~0 kg mm-2) and high hardness (>Hv500) shows its feasibility as mold materials. An example of 2 mm thick integrated circuit (IC) packaging leadframe patterns using x-ray micromachining is illustrated to prove its feasible application. On the technical side, micro-structures with a high aspect ratio of 30 were developed using a graphite membrane based x-ray mask.

Fabrication of microsieves with sub-micron pore size by laser interference lithography

Abstract: Laser interference lithography is a low-cost method for the exposure of large surfaces with regular patterns. Using this method, microsieves with a pore size of 65 nm and a pitch of 200 nm have been fabricated. The pores are formed by inverting a square array of photoresist posts with a chromium lift-off process and by subsequent reactive-ion etching using the chromium as an etch mask. The method has wider process latitude than direct formation of holes in the resist layer and the chromium mask allows for etching of pores with vertical sidewalls.

Tunable Fabry-Pérot cavities fabricated from PECVD silicon nitride employing zinc sulphide as the sacrificial layer

Abstract: The construction of self-supporting and suspended structures is one of the fundamental challenges of microelectromechanical systems (MEMS). Many technologies have been developed for the fabrication of such structures, which can be categorized into bulk or surface micromachining. Generally surface micromachining techniques rely on a high-temperature deposition process such as low pressure chemical vapour deposition to produce high-quality films. Plasma enhanced chemical vapour deposition (PECVD) can be used to deposit films at temperatures less than 300??C. PECVD of silicon nitride has not been used extensively in MEMS structures due to the material limitations created via the deposition technique, primarily controllability of the intrinsic stress and etch selectivity of the deposited film. We show here that PECVD silicon nitride can be used successfully in MEMS structures, and that the intrinsic stress is controllable through variations in the PECVD deposition parameters. A MEMS-based Fabry-P?rot cavity has been fabricated using PECVD silicon nitride as the membrane layer with ZnS as the sacrificial material. Devices with an initial 1??m cavity length typically provide a displacement of 240?nm across a 380??m membrane span for an applied bias of only 1.6?V.

Fabrication and test of thermal vertical bimorph actuators for movement in the wafer plane

Abstract: We have fabricated thermal actuators based on vertical bimorphs, which consist of silicon beams side-coated with aluminium. When they are heated by an electrical current they bend like a bimetal and produce movement in the wafer plane. The fabrication process is based on silicon-on-insulator substrates and uses standard silicon micromachining techniques combined with a special aluminium sidewall deposition process. The displacement has been measured as a function of the input power and the results have been compared with an FEA-simulation.

Electroporation microchips for in vitro gene transfection

Abstract: A detailed study of a novel electroporation (EP) microchip for in vitro gene transfection has been conducted. Electroporation is a technique with which DNA molecules can be delivered into cells in a chamber using high electric field pulses. Compared to a commercial electroporator, the EP microchip can attain the necessary electric field for the electroporation process but takes advantage of a much lower required voltage. The EP microchip overcomes the potential risk of using a high voltage, which is the drawback of current electroporation technology. Furthermore, the advantages of this EP microchip are the use of a very small amount of cells and genes, a very low applied voltage, a simple power supply and a much simpler cell preparation process. Any of these advantages are better than, or cannot be found in, a commercial electroporator. The EP microchip, consisting of a defined cell culture cavity region with thin-film electrodes made of titanium and gold, was fabricated on a glass slide using microfabrication technologies, which include evaporation, photolithography and wet-etching methods. Two different cell lines, Huh-7 and 293T, were used to demonstrate the transfection. The experimental results show that the EP microchip can successfully deliver green fluorescent protein genes into both cell lines. This work demonstrates that this EP microchip can provide in vitro gene transfection with a very small amount of cells and plasmids, requiring a much lower applied voltage and a simpler process than current commercial equipment. This EP microchip will have many useful applications in gene therapy.