Surface micromachined electrostatically actuated micro peristaltic pump

An electrostatically actuated micro peristaltic pump is reported. The micro pump is entirely surface micromachined using a multilayer parylene technology. Taking advantage of the multilayer technology, the micro pump design enables the pumped fluid to be isolated from the electric field. Electrostatic actuation of the parylene membrane using both DC and AC voltages was demonstrated and applied to fluid pumping based on a 3-phase peristaltic sequence. A maximum flow rate of 1.7 nL min^–1 and an estimated pumping pressure of 1.6 kPa were achieved at 20 Hz phase frequency. A dynamic analysis was also performed with a lumped-parameter model for the peristaltic pump. The analysis results allow a quantitative understanding of the peristaltic pumping operation, and correctly predict the trends exhibited by the experimental data. The small footprint of the micro pump is well suited for large-scale integration of microfluidics. Moreover, because the same platform technology has also been used to fabricate other devices (e.g. valves, electrospray ionization nozzles, filters and flow sensors), the integration of these different devices can potentially lead to versatile and functional micro total analysis systems (µTAS)

Design and Experimental Analysis of Ventilated Walls and "Ice House" Roofs Applications in Warm Climates

This paper contains the findings of experimental research conducted to determine the effectiveness of ventilated walls and "ice house" roof applications in hot-humid climates. Ventilated wall and "ice house" roof is the type of construction which consists of interposing an additional wall or roof skin between the standard building envelope and the exterior environment. The new skin is separated from the building envelope by an air space, which is usually vented to the ambient environment. The primary objective of such construction is to eliminate or drastically reduce the effects of solar loading on the building envelope. The information presented in this paper can enable the designer to have a better understanding of how buildings might function at various times of the day and the season. Recommendations on applications of new buildings and retrofit of existing structures are presented here as well

IT and Productivity in Developed and Developing Countries

Previous research at the cross-national level has found that IT investment is associated with significant productivity gains for developed countries but not for developing countries. Notwithstanding the lack of evidence of productivity gains, developing countries have increased their investment in IT dramatically. Given all of this investment, there is a need for research to study whether the investment has begun to pay off in greater productivity for developing countries. In this study, we employ production function analysis on new data on IT investment and productivity for 49 countries from 1985-2004, and compare the results from 1994-2004 with the earlier years (1985-1993) that were covered by Dewan and Kraemer (2000). The goal is to find out whether developing countries have been able to achieve significant productivity gains from IT investment in the more recent period as they have increased their IT capital stocks and gained experience with the use of IT. We also incorporate a set of complementary factors missing from previous studies, including telecommunications investment and prices, human resources, and foreign direct investment, to determine whether these factors have an impact on the relationship of IT to productivity. We find that for developing countries, there was no significant effect for IT capital for the 1985-1993 sample, but the relationship is positive and significant for the 1994-2004 sample. On the other hand, for developed countries, IT capital is significant across all time periods. Non-IT capital stock and labor hours also are positive and significant across all samples and time periods as expected. We also find developing countries with higher levels of tertiary education and lower telecommunication prices achieve greater productivity gains. To our knowledge, this is the first empirical research to find productivity impacts from IT investments in developing countries. The finding that developing countries only began to realize payoffs from IT investment in more recent years suggests that there may be some critical level of IT capital stock, or some minimum level of accumulated experience (human capital) required before such gains become evident. For policymakers in developing countries, these findings provide evidence that IT investments are likely to lead to productivity gains and give support for policies to promote IT investment and use

Integrated surface-micromachined mass flow controller

An integrated surface-micromachined mass flow controller (MFC) that consists of an electrostatically actuated microvalve and a thermal flow sensor is presented here. With a unique design and utilizing a multilayer Parylene process, the active microvalve and the flow sensor are integrated onto a single chip to perform closed-loop flow control. Sensitivity of the flow sensor is 55 μV/(μ/L/min) for airflow and 12.2 μV/(nL/min) for water. The valve is actuated with a 10 kHz AC signal and an applied pressure of 21 kPa can be sealed with an actuation voltage of 200 V_peak (±200 V). For flow control, both Pulse Width Modulation (PWM) and actuation voltage adjustment are demonstrated. PWM shows better performance in terms of controllability and linearity

Surface micromachined and integrated capacitive sensors for microfluidic applications

We have demonstrated an entire series of capacitive sensors using a multi-layer parylene/photoresist surface micromachining technology. The developed sensors are designed for total integration into parylene-based microfluidic systems for real-time system monitoring. Sensors have been demonstrated for the following applications: in-line pressure sensing (range: 0-35 kPa, resolution: 0.03 kPa); liquid front position and/or volumetric measurements (range: 0->50 pL, resolution: <5 pL); and dielectric measurements, which can be used to deduce fluid properties such as liquid composition. The reported sensor technology demonstrates versatility, high sensitivity, small footprints, and easy integration

It diffusion in developing countries

here is widespread belief among international agencies and development specialists in the potential value of information technology (IT) to sup-port economic and human development [11, 12]. Some question whether IT alone can have a major impact on the standard of living in developing countries, but most see it offering access to vital information and services such as weather forecasting, commodity prices, health care, and education. However, a significant digital divide exists between richer and poorer countries in the use of IT and the availability of complementary assets such as telecommunications networks and skilled IT profes-sionals. This gap has led to a public debate about what can be done to promote greater IT use so that developing coun-tries can achieve the types of benefits already being enjoyed in the industrialized world. Policymakers need to recognize that developing economies have different drivers for IT investment than their wealthier brethren

Microfabricated High-Performance Liquid Chromatography (HPLC) System with Closed-Loop Flow Control

This thesis presents the development of a microfabricated high-performance liquid chromatography (HPLC) system. The design, fabrication, and characterization of individual HPLC components such as high-pressure pumps, mixers, flow sensors, composition sensors, separation columns, filters, and detectors is presented. These individual components were then integrated to create robust, feedback-driven separation systems capable of performing gradient, reverse-phase, nanoscale HPLC. Two separate separation systems were created. The first integrated system was a microfluidic device for HPLC tandem mass spectrometry (HPLC-MS/MS) designed for proteomic applications. The second system was a portable HPLC conductivity detection (HPLC-CD) system designed for point-of-care applications such as biodetection. Both systems demonstrated good performance and repeatability. The performance of these systems is largely attributable to the development of HPLC-compatible sensors that could provide precise control over the elution profiles. These microfluidic closed-loop flow control systems represent an important advancement in the microfluidics field, where open-loop flow control is universally used, and risks becoming inadequate with the increasing complexity of microfluidic systems

Novel needle cutting edge geometry for end‐cut biopsy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135111/1/mp5253.pd