Advanced digital microfluidic biochips based on technologies such as micro-electrode-dot-array (MEDA) and active matrix (AM) provide enhanced functionality compared to conventional biochips. Owing to the larger ratio of droplet size to electrode size, these platforms allow finer control of droplets and diagonal movement. Additionally, they allow dynamic grouping of micro-electrodes to form subsystems that can perform fluidic operations. Shape morphing is a key feature of MEDA/AM biochips that results in faster fluidic operations, thereby improving the efficiency of bioassays. To establish the benefits of shape morphing, we first numerically simulate the shape morphing operation. We employ a simplified 2-D flow model incorporating interface tracking through a level-set method to numerically simulate shape morphing induced by micro-electrode actuation. We also validate our numerical results with COMSOL simulations and experiments performed on MEDA/AM biochips. The validated shape morphing operations are subsequently used to optimize droplet routing for benchmark bioassays. We propose an algorithm to significantly reduce the size of the routing problem and the time needed to solve it. With the help of this improved approach, we show that droplet morphing operations reduce the time needed to complete bioassays.

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.

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.