Microfluidic biochips are widely used in biomedical research, clinical diagnostics, and point-of-care testing. However, their complex supply chains make them vulnerable to counterfeiting, overbuilding, and intellectual property (IP) piracy. We present fluorescent carbon quantum dot (CQD) stickers1that can be integrated with the polydimethylsiloxane (PDMS) based biochips for authentication. The stickers can be plasma-bonded to biochips made of glass and silicon. A protective spin-coated PDMS layer makes them obscured and tamperproof. However, they are detectable under UV light and can be authenticated via spectral analysis. The scheme exhibits unique excitation-dependent responses associated with the variability of the CQD sizes. This makes it ideal for physical authentication. Reliability studies concerning mechanical, photonic, and thermal degradation have demonstrated highly stable results. The stability of CQDs within the PDMS, their robust excitation-based emission fluorescence response, and the use of waste polypropylene masks make this a sustainable and robust authenticator for biochips.

A hybrid high-voltage regulating charge pump is proposed for point-of-care electrokinetic concentration chip applications. The hybrid charge pump is composed of three cascaded sub-pumps. High efficiency, minimized area, wide output current range, and high regulated output voltage are achieved by selecting charge pump architectures that provide high voltage conversion gain with less number of stages. The proposed charge pump is designed and fabricated in 180 nm BCD process. Simulation results show that the proposed system provides a maximum efficiency of 48.26%, while providing a maximum output voltage of 65 V.

Flow-based microfluidic biochips (FMBs) have microvalves as key components. The physical characteristics of the microvalves vary instance-to-instance due to the inherent variability of numerous fabrication parameters. In this work, we leverage this unclonable, unpredictable instance-specific behavior and propose physically unclonable functions (PUFs) for FMBs, namely Biochip-PUFs (Bio-PUFs in short). We utilize variability in the microvalve membrane deflection response associated with the actuation pressure challenge to be our Bio-PUF parameter. Based on the distributions of the parameters measured on actual FMBs, we complement our Bio-PUF measurements via simulations of the FMB's microvalves in Comsol Multiphysics. Furthermore, we present a scheme based on the transient response of the microvalve actuation to augment the Bio-PUF authentication. The major advantage of this scheme is that we do not need any additional hardware to generate/implement the PUF module. The biochip itself can act as PUF instances while continuing to operate in normal functioning mode.

Researchers develop bioassays following rigorous experimentation in the lab that involves considerable fiscal and highly-skilled-person-hour investment. Previous work shows that a bioassay implementation can be reverse-engineered by using images or video and control signals of the biochip. Hence, techniques must be devised to protect the intellectual property (IP) rights of the bioassay developer. This study is the first step in this direction and it makes the following contributions: (1) it introduces the use of a dummy valve as a security primitive to obfuscate bioassay implementations; (2) it shows how dummy valves can be used to obscure biochip building blocks such as multiplexers and mixers; (3) it presents design rules and security metrics to design and measure obfuscation. In our preliminary work, we presented the concept through the use of sieve-valve as a dummy-valve. However, sieve-valves are difficult to fabricate. To overcome fabrication complexities, we propose a novel multi-height-valve as an obfuscation primitive. Moreover, we showcase the suitability of multi-height-valve for obfuscation through COMSOL simulations. We demonstrate the practicality of the proposal by fabricating an obfuscated biochip using multi-height valves. We assess the cost-security trade-offs associated with this solution and study the practical implications of dummy-valve based obfuscation on real-life biochips.

Microfluidic technologies find application in various safety-critical fields such as medical diagnostics, drug research, and cell analysis. Recent work has focused on security threats to microfluidic-based cyberphysical systems and defenses. So far the threat analysis has been limited to the cases of tampering with control software/hardware, which is common to most cyberphysical control systems in general; in a sense, such an approach is not exclusive to microfluidics. In this paper, we present a stealthy attack paradigm that uses characteristics exclusive to the microfluidic devices - a microfluidic trojan. The proposed trojan payload is a valve whose height has been perturbed to vary its pressure response. This trojan can be triggered in multiple ways based on time or specific operations. These triggers can occur naturally in a bioassay or added into the controlling software. We showcase the trojan application in carrying out practical attacks -contamination, parameter-tampering and denial-of-service - on a real-life bioassay implementation. Further, we present guidelines to launch stealthy attacks and to counter them.

Microfluidic biochips enable low-cost automation of biochemical protocols with numerous applications to medical diagnostics, forensics, molecular biology, and drug design. An important component of protocol design is sample preparation, which involves dilution or mixing of two or more fluids in a desired ratio of concentration factors (CF). Existing continuous-flow microfluidic biochips deploy either free-flowing networks where only a single layer of flow-channels is used devoid of any control valves, or valve-based technology where the flow-layer is augmented with a control layer of valves. While the former is easy to fabricate, reliable, and less expensive, they are typically hardwired for specific applications only. The latter class, although programmable, is expensive and prone to various manufacturing and operational defects. In this paper, we present the physical design of a microfluidic network that is free-flowing as well as programmable. The proposed valve-free network resembles a complete binary tree with serpentine obstacles embedded within its channels, and can be used to achieve a desired dilution of a sample just by proper selection of fluid concentrations to be fed as inputs under constant pressure. Simulation with COMSOL Multiphysics Software shows that the proposed network provides a powerful and versatile architecture for solution preparation with minimal control, outperforming prior approaches in terms of the accuracy of CFs and time for convergence.

Researchers develop bioassays following rigorous experimentation in the lab that involves considerable fiscal and highly-skilled-person-hour investment. Previous work shows that a bioassay implementation can be reverse engineered by using images or video and control signals of the biochip. Hence, techniques must be devised to protect the intellectual property (IP) rights of the bioassay developer. This study is the first step in this direction and it makes the following contributions: (1) it introduces use of a sieve-valve as a security primitive to obfuscate bioassay implementations; (2) it shows how sieve-valves can be used to obscure biochip building blocks such as multiplexers and mixers; (3) it presents design rules and security metrics to design and measure obfuscated biochips. We assess the cost-security trade-offs associated with this solution and demonstrate practical sieve-valve based obfuscation on real-life biochips.

Researchers develop bioassays by rigorously experimenting in the lab. This involves significant fiscal and skilled person-hour investment. A competitor can reverse engineer a bioassay implementation by imaging or taking a video of a biochip when in use. Thus, there is a need to protect the intellectual property (IP) rights of the bioassay developer. We introduce a novel 3D multilayer-based obfuscation to protect a biochip against reverse engineering.

The fully programmable valve array (FPVA) is a general-purpose programmable flow-based microfluidic platform, akin to the VLSI field-programmable gate array (FPGA). FPVAs are dynamically reconfigurable and, hence, are suitable in a broad spectrum of applications involving immunoassays and cell analysis. Since these applications are safety critical, addressing security concerns is vital for the success and adoption of FPVAs. This study evaluates the security of FPVA biochips. We show that FPVAs are vulnerable to malicious operations similar to digital and flow-based microfluidic biochips. FPVAs are further prone to new classes of attacks-tunneling and deliberate aging. This study establishes security metrics and describes possible attacks on real-life bioassays. Furthermore, we study the use of machine learning (ML) techniques to detect and classify attacks based on the golden and real-time biochip state. In order to boost the classifier's performance, we propose a smart checkpointing mechanism. Experimental results are presented to showcase: 1) best-fit ML model classifier; 2) performance of different tradeoffs in checkpointing; and 3) effectiveness of the proposed smart checkpointing scheme.