Research

• Develop hardware security measures to protect the wearable devices from unauthorized access or replacements (PUFs for wearables).

• Design, analysis and optimization of electromagnetic actuation system to navigate magnetic nanoparticles (MNPs) in microfluidic channel.

• Design of a time-varying magnetic field (TVMF) to mitigate the stiction and disaggregation of MNPs in microfluidic channel.

• Development of actuation system prototype to validate the response of TVMF.

• Synthesis and characterization of iron oxide nanoparticles.

• Development of PDMS based Y-shaped microchannel to mimic the in vivo application.

In a magnetically actuated TDDS, the MNPs are guided to the desired blood vessel by steering them from the bifurcation points using an external electromagnetic actuation (EMA) system. Meanwhile, some MNPs get stuck to the vessel wall during the steering process. To overcome this problem, an EMA system is designed using four coils and the coil parameters are optimized to efficiently steer the MNPs in a Y-shaped microchannel. The system operates by applying a time-varying magnetic field (TVMF) to navigate the MNPs in the channel efficiently. The MNPs separated from the sidewalls move ahead with the fluid flow to the desired channel and this guidance mechanism is repeated until the MNPs reach the target point.

At the outset, extensive simulations are performed to design and optimize the drug delivery system for effective steering of the MNPs using COMSOL Multiphysics. The finite element method (FEM) employed by COMSOL Multiphysics is used to numerically approximate solutions of partial differential equations (PDEs) with known boundary conditions. More precisely, the Magnetic Fields interface from AC/DC module is used to compute the magnetic field in and around the proposed electromagnetic coils. The variables that describe the current direction in coils are solved using Coil Geometry Analysis. The Coefficient Form PDE interface is used to evaluate the derivatives of the magnetic field components. A steady-state Laminar Flow interface from Computational Fluid Dynamics (CFD) module is used to compute the velocity profile of the fluid flow inside the Y-shaped channel. The Particle Tracing for Fluid Flow interface from Particle Tracing Module is used to compute the motion of particles in the Y-shaped channel. Steady-state solver is used for fluid flow and a time-dependent solver is used to compute particle trajectory. In summary, unidirectional coupling from the magnetic fields and laminar flow to the particle trajectories is exploited in this simulation as follows: first the fields with gradients and velocity profile are computed, which are subsequently utilized to define the particle trajectory in a microfluidic channel.

The design parameters obtained from the simulations discussed above are used to build a working prototype of our proposed electromagnetic actuation system for targeted drug delivery. To this end, we consider the motion of spherical magnetic particles in a Y-shaped microfluidic channel under the influence of an applied field. The Fe3O4 magnetic nanoparticles are synthesized by the chemical co-precipitation method. A PDMS based Y-shaped microchannel is fabricated by using the 3D printed mold-removal method, to mimic the in vivo application. The synthesized Fe3O4 MNPs are suspended in deionized (DI) water and injected into the Y-shaped microchannel using a syringe pump, and the flow rate is adjusted to yield a similar fluidic force as that of blood. The experimental validation of our proposed EMA system highlights enhanced efficacy in mitigating the stiction issue by alleviating the detrimental effect of the MNPs getting steered to the undesired outlet.