Tao Xu

Bio: Tao Xu is an academic researcher from Duke University. The author has contributed to research in topics: Biochip & Lab-on-a-chip. The author has an hindex of 21, co-authored 25 publications receiving 1505 citations. Previous affiliations of Tao Xu include Research Triangle Park.

Broadcast electrode-addressing for pin-constrained multi-functional digital microfluidic biochips

Abstract: Recent advances in digital microfluidics have enabled lab-on-a-chip devices for DNA sequencing, immunoassays, clinical chemistry, and protein crystallization. Basic operations such as droplet dispensing, mixing, dilution, localized heating, and incubation can be carried out using a two-dimensional array of electrodes and nanoliter volumes of liquid. The number of independent input pins used to control the electrodes in such microfluidic "biochips" is an important cost-driver, especially for disposable PCB devices that are being developed for clinical and point-of-care diagnostics. However, most prior work on biochip design-automation has assumed independent control of the electrodes using a large number of input pins. Another limitation of prior work is that the mapping of control pins to electrodes is only applicable for a specific bioassay. We present a broadcast-addressing-based design technique for pin-constrained multi-functional biochips. The proposed method provides high throughput for bioassays and it reduces the number of control pins by identifying and connecting control pins with "compatible" actuation sequences. The proposed method is evaluated using a multifunctional chip designed to execute a set of multiplexed bioassays, the polymerase chain reaction, and a protein dilution assay.

Droplet-trace-based array partitioning and a pin assignment algorithm for the automated design of digital microfluidic biochips

Abstract: Microfluidics-based biochips combine electronics with biology to open new application areas such as point-of-care medical diagnostics, on-chip DNA analysis, and automated drug discovery. Bioassays are mapped to microfluidic arrays using synthesis tools, and they are executed through the manipulation of sample and reagent droplets by electrical means. Most prior work on CAD for biochips has assumed independent control of electrodes using a large number of (electrical) input pins. Such solutions are not feasible for low-cost disposable biochips that are envisaged for many field applications. A more promising design strategy is to divide the microfluidic array into smaller partitions and use a small number of electrodes to control the electrodes in each partition. We propose a partitioning algorithm based on the concept of "droplet trace", which is extracted from the scheduling and droplet routing results produced by a synthesis tool. An efficient pin assignment method, referred to as the "Connect-5 algorithm", is combined with the array partitioning technique based on droplet traces. The array partitioning and pin assignment methods are evaluated using a set of multiplexed bioassays.

Parallel Scan-Like Test and Multiple-Defect Diagnosis for Digital Microfluidic Biochips

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. We propose a parallel scan-like testing methodology for digital microfluidic devices. A diagnosis method based on test outcomes is also proposed. The diagnosis technique is enhanced such that multiple defect sites can be efficiently located using parallel scan-like testing. Defect diagnosis can be used to reconfigure a digital microfluidic biochip such that faults can be avoided, thereby enhancing chip yield and defect tolerance. We evaluate the proposed method using complexity analysis as well as applying it to a fabricated biochip.

Integrated droplet routing in the synthesis of microfluidic biochips

Abstract: Microfluidic biochips are revolutionizing many areas of biochemistry and biomedical sciences Several synthesis tools have recently been proposed for the automated design of biochips from the specifications of laboratory protocols However, only a few of these tools address the problem of droplet routing in microfluidic arrays These methods typically rely on post-synthesis droplet routing to implement biochemical protocols Such an approach is not only time-consuming, but it also imposes an undue burden on the chip user Moreover, post-synthesis droplet routing does not guarantee that feasible droplet pathways can be found for area-constrained biochip layouts; non-routable fabricated biochips must be discarded We present a droplet-routing-aware automated synthesis tool for microfluidic biochips Droplet routability, defined as the ease with which droplet pathways can be determined, is estimated and integrated in the synthesis flow The proposed approach allows architectural-level design choices and droplet-routing-aware physical design decisions to be made simultaneously We use a large-scale protein assay as a case study to evaluate the proposed synthesis method

Automated design of pin-constrained digital microfluidic biochips under droplet-interference constraints

Abstract: Microfluidics-based biochips, also referred to as lab-on-a-chip, are devices that integrate fluid-handling functions such as sample preparation, analysis, separation, and detection. This emerging technology combines electronics with biology to open new application areas such as point-of-care diagnosis, on-chip DNA analysis, and automated drug discovery. We propose a design automation method for pin-constrained biochips that manipulate nanoliter volumes of discrete droplets on a microfluidic array. In contrast to the direct-addressing scheme that has been studied thus far in the literature, we assign a small number of independent control pins to a large number of electrodes in the biochip, thereby reducing design complexity and product cost. The design procedure relies on a droplet-trace-based array partitioning scheme and an efficient pin assignment technique, referred to as the “Connect-5 algorithm.” The proposed method is evaluated using a set of multiplexed bioassays.

Droplet-based surface modification and washing

Abstract: The present invention relates to droplet-based surface modification and washing. According to one embodiment, a method of splitting a droplet is provided, the method including providing a droplet microactuator including a droplet including one or more beads and immobilizing at least one of the one or more beads. The method further includes conducting one or more droplet operations to divide the droplet to yield a set of droplets including a droplet including the one or more immobilized beads and a droplet substantially lacking the one or more immobilized beads.

The Era of Digital Health: A Review of Portable and Wearable Affinity Biosensors

Abstract: Digital health facilitated by wearable/portable electronics and big data analytics holds great potential in empowering patients with real‐time diagnostics tools and information. The detection of a majority of biomarkers at trace levels in body fluids using mobile health (mHealth) devices requires bioaffinity sensors that rely on “bioreceptors” for specific recognition. Portable point‐of‐care testing (POCT) bioaffinity sensors have demonstrated their broad utility for diverse applications ranging from health monitoring to disease diagnosis and management. In addition, flexible and stretchable electronics‐enabled wearable platforms have emerged in the past decade as an interesting approach in the ambulatory collection of real‐time data. Herein, the technological advancements of mHealth bioaffinity sensors evolved from laboratory assays to portable POCT devices, and to wearable electronics, are synthesized. The involved recognition events in the mHealth affinity biosensors enabled by bioreceptors (e.g., antibodies, DNAs, aptamers, and molecularly imprinted polymers) are discussed along with their transduction mechanisms (e.g., electrochemical and optical) and system‐level integration technologies. Finally, an outlook of the field is provided and key technological bottlenecks to overcome identified, in order to achieve a new sensing paradigm in wearable bioaffinity platforms.

Droplet-Based Particle Sorting

Abstract: The present invention relates to droplet-based particle sorting. According to one embodiment, a droplet microactuator is provided and includes: (a) a suspension of particles; and (b) electrodes arranged for conducting droplet operations using droplets comprising particles. A method of transporting a particle is also provided, wherein the method includes providing a droplet comprising the particle and transporting the droplet on a droplet microactuator.

System-on-Chip Test Architectures: Nanometer Design for Testability

Abstract: Modern electronics testing has a legacy of more than 40 years. The introduction of new technologies, especially nanometer technologies with 90nm or smaller geometry, has allowed the semiconductor industry to keep pace with the increased performance-capacity demands from consumers. As a result, semiconductor test costs have been growing steadily and typically amount to 40% of today's overall product cost. This book is a comprehensive guide to new VLSI Testing and Design-for-Testability techniques that will allow students, researchers, DFT practitioners, and VLSI designers to master quickly System-on-Chip Test architectures, for test debug and diagnosis of digital, memory, and analog/mixed-signal designs. KEY FEATURES * Emphasizes VLSI Test principles and Design for Testability architectures, with numerous illustrations/examples. * Most up-to-date coverage available, including Fault Tolerance, Low-Power Testing, Defect and Error Tolerance, Network-on-Chip (NOC) Testing, Software-Based Self-Testing, FPGA Testing, MEMS Testing, and System-In-Package (SIP) Testing, which are not yet available in any testing book. * Covers the entire spectrum of VLSI testing and DFT architectures, from digital and analog, to memory circuits, and fault diagnosis and self-repair from digital to memory circuits. * Discusses future nanotechnology test trends and challenges facing the nanometer design era; promising nanotechnology test techniques, including Quantum-Dots, Cellular Automata, Carbon-Nanotubes, and Hybrid Semiconductor/Nanowire/Molecular Computing. * Practical problems at the end of each chapter for students.

A High-Performance Droplet Routing Algorithm for Digital Microfluidic Biochips

Abstract: In this paper, we propose a high-performance droplet router for a digital microfluidic biochip (DMFB) design. Due to recent advancements in the biomicro electromechanical system and its various applications to clinical, environmental, and military operations, the design complexity and the scale of a DMFB are expected to explode in the near future, thus requiring strong support from CAD as in conventional VLSI design. Among the multiple design stages of a DMFB, droplet routing, which schedules the movement of each droplet in a time-multiplexed manner, is one of the most critical design challenges due to high complexity as well as large impacts on performance. Our algorithm first routes a droplet with higher by passibility which is less likely to block the movement of the others. When multiple droplets form a deadlock, our algorithm resolves it by backing off some droplets for concession. The final compaction step further enhances timing as well as fault tolerance by tuning each droplet movement greedily. The experimental results on hard benchmarks show that our algorithm achieves over 35 x and 20 x better routability with comparable timing and fault tolerance than the popular prioritized A* search and the state-of-the-art network-flow-based algorithm, respectively.