Electric Field Enhancement of 3D Nano-spikes Devices for Energy Efficient Biological Manipulations

Energy efficient biological manipulations i.e., electroporation (EP), cell lysis (CL) is highly desirable in portable lab-on-a-chip, micro total analysis systems, and smartphone based systems due to power limitations. We employed highly periodic 3D nano-spikes (NSPs) for electric field enhancement due to their high aspect-ratio (λ). The enhance electric field E_nsp was defined by enhancement factor α which depend on λ. 3D nano-spikes were fabricated with controllable dimensions i.e., length L_ns, base radius R_ns by using scalable and cost-effective electrochemical anodization and etching processes (Fig. 1). Numerical simulations were performed for electric field distribution at NSPs using a commercial finite element method (FEM) package (COMSOL Multiphysics 4.2, COMSOL Ltd., USA). The NSP electrode was separated from counter electrode by distance d and cell suspension medium was considered between electrodes with relative permittivity and conductivity of 77.4 ± 5% and 1.7 S/m ± 10%, respectively. The boundary condition was fixed potential which was applied between electrodes. Simulation results indicate that applied electric field E_a was enhanced especially near the tip of NSPs and α can be determined by E_ns/E_a (Fig. 1). 𝛼 was estimated in the range of ~5.9 to 8.9 for NSPs with λ of 2 to 3 respectively (Fig. 1). Efficient EP and CL were conducted on 3D nano-spike devices at energy (0.5-2 mJ/mL) which is 2 to 3 order of magnitude lower than traditional systems [1,2].