A recent advancement in the study of drug development for cardiovascular diseases is based on measuring the
mechanical response of a single cardiomyocyte to various drug concentrations. This method requires delivering a
specific dose of the drug over a short period of time while measuring the forces exerted by a cell that is kept inside a
microchamber. However, the exact drug dosage is difficult to control for rapid variations in drug concentration, which
hinders the accuracy of the measurements. This paper reports a highly sensitive technique for accurate and real-time
measurement of minute variations in drug concentration. The fluid electrical conductivity is monitored using an array of
electrodes along a micro-channel that eventually leads to the microchamber where the cardiomyocyte is placed. The
microfluidic setup is fabricated through bonding of a moulded Polydimethylsiloxane (PDMS) layer to a glass substrate
with patterned gold electrodes. The real-time differential measurements let us measure the local drug concentration with
accuracies of better than 10pMol/mL. By using the data from all of the array electrodes, the profile of the drug plug as it
travels along the microchannel from the injection point to the cell location can be derived with high precision. The multidomain
numerical simulations of the microfluidic setup are in line with the measured experimental data. Our technique
can be easily integrated into many existing and new designs thus providing a robust approach for label-free measurement
of fluid properties in cell viability studies.
This paper presents a method for etching millimetre-deep trenches in commercial grade PMMA using deep-UV
at 254 nm. The method is based on consecutive cycles of irradiation and development of the exposed areas, respectively.
The exposure segment is performed using an inexpensive, in-house built irradiation box while the development part is
accomplished using an isopropyl alcohol (IPA):H2O developer. The method was tested and characterized by etching
various dimension square test structures in commercial grade, mirrored acrylic. The undercut of the sidewalls due to the
uncollimated nature of the irradiation light was dramatically alleviated by using a honeycomb metallic grid in between
the irradiation source and the acrylic substrate and by rotating the latter using a direct current (DC) motor-driven stage.
By using an extremely affordable set-up and non-toxic, environmentally friendly materials and substances, this process
represents an excellent alternative to microfabricating microfluidic devices in particular and high aspect ratio structures
in general using PMMA as substrate.
Classic photo gate APS uses a MOS capacitor that can capture incident illumination with a potential well created under
the photogate. The major drawback of such a technology is the absorption of shorter wavelength by the polysilicon gate
resulting in a higher sensitivity in the red visible spectrum than in the blue range. To reduce this we previously had
experimentally shown that a multifinger photo gate APS designs with 0.72Νm fingers implemented in the 0.18 μm
CMOS technology have a significant increase in sensitivity of 1.7 times the standard photo gate APS. Using advanced
2-dimensional device simulations had shown that the fringing fields form the these fingers would create a potential well
shape that approached that of the standard fully covered photo gate, but with large open areas which would have less
optical absorption. Reducing the gate widths resulted in higher efficiency of photo carriers generated in the larger open
areas while keeping the potential well shape desired. In this work, we use optical simulation package on the 2D device
simulation tools to simulate the multi finger photo gate designs with white light illumination. Sensitivity of the pixel is
calculated as the count of total number of photocarriers that are collected by the potential well for a given exposure
cycle. All the multifinger designs achieved a significant increase in efficiency with respect to the standard photogate
APS design, with the peak sensitivity of 550% by the 7finger design with a gate width of 0.25μm.
We present initial results on the fabrication and testing of micropatternable conductive nanocomposite polymer (C-NCP)
electrodes for tissue impedance measurements. We present these proof-of-concept results as a first step toward the
realization of our goal: an improved Electrical Impedance Scanning (EIS) system, whereby tissue can be scanned for
cancerous tissue and other anomalies using large arrays of highly flexible microfabricated electrodes. Previous
limitations of existing EIS system are addressed by applying polymer based microelectromechanical system (MEMS)
technology. In particular, we attempt to minimize mechanical skin contact issues through the use of highly compliant
elastomeric polymers, and increase the spatial resolution of measurements through the development of microelectrodes
that can be micropatterned into large, highly dense arrays. We accomplish these improvements through the development
of C-NCP electrodes that employ silver nanoparticle fillers in an elastomer polymer base that can be easily patterned
using conventional soft lithography techniques. These new electrodes are tested on conventional tissue phantoms that
mimic the electrical characteristics of human tissue. We characterize the conductivity of the electrodes (average
resistivity of 7x10-5 ohm-m +/- 14.3% at 60 wt-% of silver nanoparticles), and further employ the electrodes for
impedance characterization via Cole-Cole plots to show that measurements employing C-NCP electrodes are comparable
to those obtained with normal macroscopic metal electrodes. We also demonstrate anomaly detection using our highly
flexible Ag/AgCl C-NCP electrodes on a tissue phantom.
An inexpensive and rapid micro-fabrication process for producing PMMA microfluidic components has been presented.
Our proposed technique takes advantages of commercially available economical technologies such as the silk screen
printing and UV patterning of PMMA substrates to produce the microfluidic components. As a demonstration of our
proposed technique, we had utilized a homemade deep-UV source, λ=254nm, a silk screen mask made using a local
screen-printing shop and Isopropyl alcohol - water mixture (IPA-water) as developer to quickly define the microfluidic
patterns. The prototyped devices were successfully bonded, sealed, and the device functionality tested and demonstrated.
The screen printing based technique can produce microfluidic channels as small as 50 micrometers quite easily, making
this technique the most cost-effective, fairly high precision and at the same time an ultra economical plastic microfluidic
components fabrication process reported to date.
A 2-dimensional device simulation of Multi finger active pixel sensors is investigated for obtaining enhanced pixel
sensitivity. Photo gate APS use a MOS capacitor that can capture incident illumination with a potential well created
under the photo gate. The major drawback of such a technology is the absorption of shorter wavelength by the
polysilicon gate resulting in a higher sensitivity in the red visible spectrum than in the blue range. In our previous work
we implemented 0.18μm CMOS standard and multi fingered photo gate design where the enclosed detection area is
divided by 3, 5 and 7 fingers. The experimental results showed that fringing field created potential wells for the 3 and 5
finger photo gate designs have 1.7 times higher collection of photo carriers over the standard photo gate. The device
simulation showed that fringing fields from the edges of the poly gates created potential wells that fully covered the open
silicon areas allowing light conversion without the optical absorption in the poly silicon gates. Extending simulations to
0.5 μm, 0.25 μm and 0.18 μm multifinger poly gates showed that the fringing fields stayed the same width as the gates
shrunk, so that as the number of fingers increased the potential well in the open areas became more uniform. The device
sensitivity based on the potential well locations, and previous experimental results, suggested peak efficiencies for the
0.5 μm design as 7 fingers, 0.25 μm at 9 fingers and 0.18 μm at 11 fingers. Peak efficiency was projected to be 2.2 times
that of a standard photogate.
Photogate APS pixels use a MOS capacitor created potential well to capture photocarriers. However, optical
absorption of the poly-silicon gate reduces photon transmission. We investigate multi-fingered photogates with
openings in the gate to increase photon collection. 0.18 μm CMOS standard and multi-fingered photogates were
implemented where the enclosed detection area is divided by 1, 3 and 5 poly fingers. Preliminary response comparison
with standard photogates suggested the sensitivity of 1-finger pixels dropped ~22% implying open areas collected 62%
of the photocarriers. The sensitivity of 3 and 5 finger pixels increased ~33 - 49% over standard, with open area
collection ~170 - 290% more photocarriers due to fringing field created potential wells. These results indicated at least 66% of the incident light is absorbed by the poly-silicon gate. In spectral response multi-fingered pixels showed an increase in sensitivity in the red (631 nm) - yellow (587 nm) - green (571 nm) wavelengths but a relative decline in the blue (470 nm) possibly due to more absorption in the Silicon Nitride insulator layers. Some Silicon Nitride (SixNy) compositions have higher absorption coefficients in the Blue than poly-silicon and thus may dominate the absorption in these photogates structures. Extended analysis on the potential well formation in the multi-fingered photogates was perform using 2-D device simulation. Simulated multi-fingered photogates showed the strength of the fringing field increased as the open area spacing between poly-fingered decreases; with the 5-finger having a nearly uniform depleted region over the entire photogate area.
Poly(dimethylglutarimide) (PMGI) is a resist that is commonly used in bilayer and trilayer imaging applications. PMGI can be exposed using various radiation sources including deep UV. Currently, there are only two developers for PMGI reported in the literature: tetramethylammonium hydroxide and tetraethylammonium hydroxide. We introduce a new developer for PMGI, a mixture of isopropanol (IPA) and water. Samples were irradiated with deep UV at 254 nm. The IPA/water developer exhibits rapid dissolution of exposed PMGI, of many microns per minute. However, PMGI exhibits high absorption at 254 nm, so the development depth is limited. The depth limit, after a critical dose, increases linearly with the exposure dose.
We are currently developing basic building blocks for creating digital logic units that are based on mechanical components. Transistors, which are semiconductor devices, rely on doping to change intrinsic semiconductor to extrinsic semiconductors. However, at low or high temperatures, that control is impossible as semiconductors revert to intrinsic behaviour. Also, semiconductors exhibit various complications under ionizing (radiation) environment.
We have fabricated logic units using micro-mechanical relays using MEMS technology. The logic units consist of a micro-mechanical relay with three electrical gates. The mechanical relay is fabricated with a cantilever over an airgap, and is operated by applying voltage to the gate. The applied voltage creates an electric force between the gate and a cantilever structure. The electrostatic force arches the cantilever into electrical contact. Since the operation does not depend on controlling the type of charge carriers, the proposed method does not suffer from the limitations shared by semiconductors. With different input combinations applied to the gates of the device, development of MEMS mechanical logic, leading to general digital circuits, is possible. Characterization of the devices is performed, which includes operation times, operation voltages, and maximum
currents. Design, fabrication and testing of these micro-mechanical logic elements will be presented in the paper.
Microsystems often require switches or mechanisms to provide two stable states. In answer to this need, we design a novel micromechanical bistable switch based on the locking mechanism commonly used in extension ladders. This switch was designed and fabricated through the multiuser MEMS processes (MUMPs). Actual performance of the switch was videotaped, analyzed, and compared with theory and simulation. This design was fully functional on the first design iteration, and can easily be extended to provide multiple stable states. We outline the design, simulation, and results from the testing of the microfabricated system.
We present an extension to the ray-transfer matrix method, which is often used to characterize optical systems. The main purpose of the extended method is to model micro-optical-bench systems that are usually manufactured using surface micromachining and other microfabrication technologies. Using a homogeneous coordinate system to extend standard ray-transfer matrices allows the matrix notation to account for manufacturing tolerances. As an example of this method's usefulness, we calculate the coupling losses in a surface micromachined fiber-optic switch.
The paper extends the work done using micro-fabricated hinges in surface micromachining to create fully 3D devices. These devices include free-space micro-optic systems and various sensors. While these applications are interesting, the assembly process is difficult. We present the basic theory and process necessary to perform the assembly using electrostatic interactions. The process is easy and reliable. We were able to lift early prototype mirrors with voltages as low as 35 volts.
We report the fabrication of a microfluidic biochip integrated with an acoustic wave sensor that can be used to characterize the contraction of single cardiac (heart) muscle cells. The work will lead to rapid analysis of single muscle cells in response to various drugs by determining changes in mass and viscoelastic properties during cell contraction and relaxation. The microfabricated device is a combination of a top cover plate which is a glass substrate containing etched channels and a bottom plate which is an AT-cut quartz crystal with excitation electrodes. The glass plate is micromachined with a network of channels and chambers, which is intended for delivery of fluids, selection and retention of single muscle cells. The bottom plate (quartz crystal) comprises all the patterned electrodes for acoustic wave launching and detection. The quartz plate is operated in the thickness-shear acoustic wave mode.
Currently available commercial endoscopic graspers do not have any built-in sensors. Thus, the surgeon does not have any tactile feed-back to manipulate tissues safely. This paper reports on the design, fabrication and testing of a semiconductor micro-strain gauge endoscopic tactile sensor. This sensor consists of two semiconductor micro-strain gauge sensors which are positioned at the back face of an endoscopic grasper. It can measure the magnitude and the position of the applied force with only two sensing elements. The amplification system for the strain gauge is also designed and fabricated. It is shown that when a force is applied to the endoscopic grasper, the magnitude of the applied force can be visually seen in an LED device. The position of the applied force is obtained by combining the output from two insulated strain gauges. We have shown that the grasper operates in a wet environment. It exhibits high force sensitivity, large dynamic range, and good linearity. The sensor is integrated with a commercial endoscopic tool. The advantages and disadvantages of the system are also discussed.
In this article, a micromachining technique is described which is an improvement to our previous technique. It allows metallic sharp and self-aligned tips to be fabricated for use as a gas detector. The fabrication technique has important advantages which makes it applicable to a wide variety application, in particular gas detection. These include simplicity and a low manufacturing cost. These tips were designed and fabricated with standard IC microfabrication technologies. However, the major highlight and achievement is the use of a low-resolution mask to position sharp tips very close to a second electrode in a simple self-aligned process. The detector exhibits a linear sensitivity response. The minimum-measured sensitivity of the detector, for the selected sample gas (CH3COOH), is 14 ppm and this was accomplished at a modest operating voltage of only 5 V. The voltage versus measured current of the detector, reveals a exponential behavior which indicates the field ionization to be responsible for detection process.
In this work, we have developed a simple method to fabricate 3D microstructures which eliminates the use of photoresist as molding material. Our method of pattern transfer exploits the anisotropic etch of silicon using EDP or TMAH which allows fabrication of unique structures that would have not been possible by the photoresist-mold method. In this technology the etched silicon substrate itself is used as the mold for subsequent electroplating process to deposit metallic material such as gold, nickel, or iron-nickel alloy. These electroplated microstructures can be easily removed from the silicon mold by choosing an appropriate seed layer which gives poor adhesion to silicon or silicon dioxide substrate. Using this technology metallic microstructures with thicknesses of 300 micrometers has been fabricated to demonstrate the feasibility. We have also fabricated a sharp tip, pyramidal structures suitable for ionization detectors in an integrated micromachined gas chromatographic system.
A micromachined pressure sensor that is suitable for integrating on the tip of the grasper of an endoscopic surgical instrument is presented. Device operation to detect the pressure applied on the body tissues during endoscopic surgery is based on the change in the capacitance between a 5 micrometers thin boron doped silicon membrane and 1 micrometers thick Aluminium electrodes sputtered inside 15 micrometers deep cavities etched in glass. The design, structural optimization for obtaining high sensitivity and the fabrication process for the device are presented. The device has a peak sensitivity of 500 pFmm2/N. The range of the pressure sensor is from 0.01 N/mm2 up to 0.1 N/mm2 which is suitable for measuring the pressure on various tissues inside the body during endoscopic surgery. Since the device simulates the teeth like surface of the existing grasper it is possible to integrate the device on the tip of the grasper of the endoscopic surgical instrument.
KEYWORDS: Transducers, Sensors, Signal processing, Silicon, Magnetic sensors, Micromachining, System integration, Semiconducting wafers, Chemical fiber sensors, Optical sensors
In the paper we discuss possible solutions to problems pertaining the implementation of integrated transducer systems, based on examples of WSI image transducers, magnetic field sensors and tactile sensors arrays, as well as arrays of chemical sensors. We also present the issues common to large area transducer arrays, such as building-in redundancy into WSI transducer arrays, and frequency domain circuits for the future communication pathway in integrated transducer systems. Advantages of standard CMOS technology, enhanced with various post-fabrication processes such as silicon micromachining and laser linking, are also stressed.
We report on the performance of a flat-panel thermal display technology, prototype developed at NIST in collaboration with Simon Fraser University and Optical E. T. C., for dynamic thermal scene simulation (DTSS). The pixel elements of the display are composed of thermally-isolated resistive heaters. The main innovation is the fabrication method which uses commercial CMOS integrated circuit (IC) foundries. This method produces a low- manufacturing-cost, high-yield, thermal display technology. Circuits for drive and control are monolithically integrated on the display. The microheating element has a thermal time constant of a few milliseconds and a temperature range of operation from ambient to over 1000 degree(s)C. A 16 X 16 pixel array with a 0.2 mm pixel pitch is presented as a demonstration of the concept; however, the circuit design supports larger sizes (e.g., 256 X $256). This display technology is compatible with DTSS requirements for laboratory and fieldable built-in test/built-in test equipment (BIT/BITE) applications.
SC236: Polysilicon Surface Micromachine Technology and Devices
This course is designed to introduce newcomers to micromachining technology and concepts as well as those with a basic familiarity with integrated circuit manufacturing technology about the emerging field of Micro Electro Mechanical Systems (MEMS). Both manufacturing technologies for these devices and examples of sensor and actuator devices will be presented. The course focuses on polysilicon surface micromachining, but will also include a brief overview of other MEMS manufacturing technologies and devices.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.