Surface-modified elastomeric nanofluidic devices for single nanoparticle trapping

Our work focuses on the development of simpler and effective production of nanofl uidic devices for high-throughput charged single nanoparticle trapping in an aqueous environment. Single nanoparticle confi nement using electrostatic trapping has been an effective approach to study the fundamental properties of charged molecules under a controlled aqueous environment. Conventionally, geometry-induced electrostatic trapping devices are fabricated using SiOx-based substrates and comprise nanochannels imbedded with nanoindentations such as nanopockets, nanoslits and nanogrids. These geometry-induced electrostatic trapping devices can only trap negatively charged particles, and therefore, to trap positively charged particles, modifi cation of the device surface is required. However, the surface modifi cation process of a nanofl uidic device is cumbersome and time consuming. Therefore, here, we present a novel approach for the development of surface-modifi ed geometry-induced electrostatic trapping devices that reduces the surface modifi cation time from nearly 5 days to just a few hours. We utilized polydimethylsiloxane for the development of a surface-modifi ed geometry-induced electrostatic trapping device. To demonstrate the device effi ciency and success of the surface modifi cation procedure, a comparison study between a PDMS-based geometryinduced electrostatic trapping device and the surface-modifi ed polydimethylsiloxane-based device was performed. The device surface was modifi ed with two layers of polyelectrolytes (1: poly(ethyleneimine) and 2: poly (styrenesulfonate)), which led to an overall negatively charged surface. Our experiments revealed the presence of a homogeneous surface charge density inside the fl uidic devices and equivalent trapping strengths for the surfacemodifi ed and native polydimethylsiloxane-based geometry-induced electrostatic trapping devices. This work paves the way towards broader use of geometry-induced electrostatic trapping devices in the fi elds of biosensing, disease diagnosis, molecular analysis, fl uid quality control and pathogen detection.