Concurrent testing of digital microfluidics-based biochips

Abstract

We present a concurrent testing methodology for detecting catastrophic faults in digital microfluidics-based biochips and investigate the related problems of test planning and resource optimization. We first show that an integer linear programming model can be used to minimize testing time for a given hardware overhead, for example, droplet dispensing sources and capacitive sensing circuitry. Due to the NP-complete nature of the problem, we also develop efficient heuristic procedures to solve this optimization problem. We apply the proposed concurrent testing methodology to a droplet-based microfluidic array that was fabricated and used to perform multiplexed glucose and lactate assays. Experimental results show that the proposed test approach interleaves test application with the biomedical assays and prevents resource conflicts. The proposed method is therefore directed at ensuring high reliability and availability of bio-MEMS and lab-on-a-chip systems, as they are increasingly deployed for safety-critical applications.

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

“…A probe cell is positioned at the electrode in front of the sink reservoir to analyze the test outcome using capacitive detection. Despite its effectiveness for detecting electrode shorts as explained in [19], testing based on an Euler path suffers from long test application time. This approach uses only one droplet to traverse the complete microfluidic array, irrespectively of the array size.…”

“…Such a diagnosis method is inefficient since defect-free cells are tested multiple times. Moreover, as in [17], the method proposed in [19] also leads to a test plan that is specific to a target biochip. If the array dimensions are changed, the test plan must be completely altered.…”

“…Moreover, to facilitate chip testing in the field, test plans need to be programmed into a microcontroller. However, the hardware implementations of test plans from [17] and [19] are prohibitively expensive, especially for low cost, disposable biochips. Therefore, there is a need for test and diagnosis methods that are efficient and amenable to low-cost hardware implementation of test procedures.…”

“…No additional diagnosis steps are needed. In contrast, Euler-path-based testing [19] reply on a binary search process to determine the exact location of the defect. Thus, parallel scan-like test saves time for many testing applications where only defect-type information is needed.…”

Automated Design of Microfluidics-Based Biochips: Connecting Biochemistry to Electronics CAD

“…These can occur during operation due to an unexpected biochemical reaction, or changes in operational environment, e.g., temperature variation. We have proposed a unified test methodology for digital microfluidic biochips, whereby faults can be detected by controlling and tracking droplet motion electrically [39,40]. Test stimuli droplets containing a conductive fluid (e.g., KCL solution) are dispensed from the droplet source.…”