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Author

Tao Xu

Other affiliations: Duke University
Bio: Tao Xu is an academic researcher from Cisco Systems, Inc.. The author has contributed to research in topics: Logic gate & Digital microfluidics. The author has an hindex of 3, co-authored 3 publications receiving 62 citations. Previous affiliations of Tao Xu include Duke University.

Papers
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Journal ArticleDOI
TL;DR: This paper addresses fundamental biochip operations, such as droplet dispensing, droplet transportation, mixing, splitting, and capacitive sensing, and evaluates the proposed test methods using simulations as well as experiments for a fabricated biochip.
Abstract: Dependability is an important attribute for microfluidic biochips that are used for safety-critical applications, such as point-of-care health assessment, air-quality monitoring, and food-safety testing. Therefore, these devices must be adequately tested after manufacture and during bioassay operations. Known techniques for biochip testing are all function oblivious (i.e., while they can detect and locate defect sites on a microfluidic array, they cannot be used to ensure correct operation of functional units). In this paper, we introduce the concept of functional testing of microfluidic biochips. We address fundamental biochip operations, such as droplet dispensing, droplet transportation, mixing, splitting, and capacitive sensing. Long electrode actuation times are avoided to ensure that there is no electrode degradation during testing. The functional testing of pin-constrained biochips is also studied. We evaluate the proposed test methods using simulations as well as experiments for a fabricated biochip.

59 citations

09 May 2012
TL;DR: In this paper, microfluidic logic gates are implemented through basic droplet-handling operations such as transporting, merging and splitting, and the same input-output interpretation enables the cascading of gates to create nontrivial computing systems.
Abstract: Microfluidic computing is an emerging application for microfluidics technology. We propose microfluidic logic gates based on digital microfluidics. Using the principle of electrowetting-on-dielectric, AND, OR, NOT and XOR gates are implemented through basic droplet-handling operations such as transporting, merging and splitting. The same input-output interpretation enables the cascading of gates to create nontrivial computing systems. We present a potential application for microfluidic logic gates by implementing microfluidic logic operations for on-chip HIV test.

4 citations

Book ChapterDOI
14 Sep 2008
TL;DR: The principle of electrowetting-on-dielectric, AND, OR, NOT and XOR gates are implemented through basic droplet-handling operations such as transporting, merging and splitting, which enables the cascading of gates to create nontrivial computing systems.
Abstract: Microfluidic computing is an emerging application for microfluidics technology. We propose microfluidic logic gates based on digital microfluidics. Using the principle of electrowetting-on-dielectric, AND, OR, NOT and XOR gates are implemented through basic droplet-handling operations such as transporting, merging and splitting. The same input-output interpretation enables the cascading of gates to create nontrivial computing systems. We present a potential application for microfluidic logic gates by implementing microfluidic logic operations for on-chip HIV test.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: This paper proposes the first reagent-saving mixing algorithm for biochemical samples of multiple target concentrations, which not only minimizes the consumption of reagents, but it also reduces the number of waste droplets and the sample preparation time by preparing the target concentrations concurrently.
Abstract: Recent advances in digital microfluidics have led to the promise of miniaturized laboratories, with the associated advantages of high sensitivity and less human-induced errors. Front-end operations such as sample preparation play a pivotal role in biochemical laboratories, and in applications in biomedical engineering and life science. For fast and high-throughput biochemical applications, preparing samples of multiple target concentrations sequentially is inefficient and time-consuming. Therefore, it is critical to concurrently prepare samples of multiple target concentrations. In addition, since reagents used in biochemical reactions are expensive, reagent-saving has become an important consideration in sample preparation. Prior work in this area does not address the problem of reagent-saving and concurrent sample preparation for multiple target concentrations. In this paper, we propose the first reagent-saving mixing algorithm for biochemical samples of multiple target concentrations. The proposed algorithm not only minimizes the consumption of reagents, but it also reduces the number of waste droplets and the sample preparation time by preparing the target concentrations concurrently. The proposed algorithm is evaluated on both real biochemical experiments and synthetic test cases to demonstrate its effectiveness and efficiency. Compared to prior work, the proposed algorithm can achieve up to 41% reduction in the number of reagent droplets and waste droplets, and up to 50% reduction in sample preparation time.

76 citations

Journal ArticleDOI
TL;DR: This paper proposes the first approach for automated testing of flow-based microfluidic biochips that are designed using membrane-based valves for flow control that is based on a behavioral abstraction of physical defects in microchannels and valves.
Abstract: Recent advances in flow-based microfluidics have led to the emergence of biochemistry-on-a-chip as a new paradigm in clinical diagnostics and biomolecular recognition. However, a potential roadblock in the deployment of microfluidic biochips is the lack of test techniques to screen defective devices before they are used for biochemical analysis. Defective chips lead to repetition of experiments, which is undesirable due to high reagent cost and limited availability of samples. Prior work on fault detection in biochips has been limited to digital (“droplet”) microfluidics and other electrode-based technology platforms. The paper proposes the first approach for automated testing of flow-based microfluidic biochips that are designed using membrane-based valves for flow control. The proposed test technique is based on a behavioral abstraction of physical defects in microchannels and valves. The flow paths and flow control in the microfluidic device are modeled as a logic circuit composed of Boolean gates, which allows test generation to be carried out using standard automatic test pattern generation tools. The tests derived using the logic circuit model are then mapped to fluidic operations involving pumps and pressure sensors in the biochip. Feedback from pressure sensors can be compared to expected responses based on the logic circuit model, whereby the types and positions of defects are identified. We show how a fabricated biochip can be tested using the proposed method, and demonstrate experimental results for two additional fabricated chips.

65 citations

Proceedings ArticleDOI
18 Mar 2013
TL;DR: This work describes the first integrated demonstration of cyberphysical coupling in digital microfluidics, whereby errors in droplet transportation on the digitalmicrofluidic platform are detected using capacitive sensors, the test outcome is interpreted by control hardware, and software-based error recovery is accomplished using dynamic reconfiguration.
Abstract: Advances in digital microfluidics and integrated sensing hold promise for a new generation of droplet-based biochips that can perform multiplexed assays to determine the identity of target molecules. Despite these benefits, defects and erroneous fluidic operations remain a major barrier to the adoption and deployment of these devices. We describe the first integrated demonstration of cyberphysical coupling in digital microfluidics, whereby errors in droplet transportation on the digital microfluidic platform are detected using capacitive sensors, the test outcome is interpreted by control hardware, and software-based error recovery is accomplished using dynamic reconfiguration. The hardware/software interface is realized through seamless interaction between control software, an off-the-shelf microcontroller and a frequency divider implemented on an FPGA. Experimental results are reported for a fabricated silicon device and links to videos are provided for the first-ever experimental demonstration of cyberphysical coupling and dynamic error recovery in digital microfluidic biochips.

63 citations

Journal ArticleDOI
TL;DR: This work presents the first synthesis approach that can be used for MEDA biochips and presents the proposed synthesis method targeting reservoir placement, operation scheduling, module placement, routing of droplets of various sizes, and diagonal movement ofdroplets in a two-dimensional array.
Abstract: A digital microfluidic biochip (DMFB) is an attractive technology platform for automating laboratory procedures in biochemistry. In recent years, DMFBs based on a microelectrode-dot-array (MEDA) architecture have been demonstrated. However, due to the inherent differences between today's DMFBs and MEDA, existing synthesis solutions for biochemistry mapping cannot be utilized for MEDA biochips. We present the first synthesis approach that can be used for MEDA biochips. We first present a general analytical model for droplet velocity and validate it experimentally using a fabricated MEDA biochip. We then present the proposed synthesis method targeting reservoir placement, operation scheduling, module placement, routing of droplets of various sizes, and diagonal movement of droplets in a two-dimensional array. Simulation results using benchmarks and experimental results using a fabricated MEDA biochip demonstrate the effectiveness of the proposed synthesis technique.

49 citations

Book ChapterDOI
18 Oct 2009
TL;DR: Achievable timing information rates, usable when all the molecules are indistinguishable, are obtained for microtubules propagating in a narrow kinesin-lined channel.
Abstract: In this paper, active transport molecular communication is analyzed for microfluidic applications. It is shown how to adapt existing information-theoretic results to this new scenario. Achievable timing information rates, usable when all the molecules are indistinguishable, are obtained for microtubules propagating in a narrow kinesin-lined channel.

41 citations