Introduction Dielectrophoresis(DEP) in an effect of polarizable objects experiencing force in a spatially inhomogenous electric fields. This effect has been widely used in lab-on-a-chip applications for guiding analytes on the chip, sorting particles by volume and dielectric properties. A new emerging branch of DEP applications is called nano-dielectrophoresis, it aims at using extremely small nanoconstrictions and nanogaps to achieve high electric field gradients while applying minimal voltages 1-10V at the RF frequency range. This effort allows 2 major benefits: it allows working with single analyte entities (single nanoparticles or even molecules) and avoiding all adverse effects that can arise from heating, AC electroosmotic flows and simply electrochemical reactions that can arise from applying large voltages in solution. Typical experiment is this setting would involve trapping the analytes in the DEP trapping hotspot and studying them using optical microscopy (See figure).
The problem The nanogap electrodes in DEP are prone to electrostatic discharge, which leads to enlargement of the nanogaps that renders samples unusable. In practice this is circumvented by a range of precautions on the level of the chip (see figure) and the circuitry to constantly keep the electrodes short-circuited up until the measurement begins. This approach works, but it introduces a lot of risk and additional logistics around the experiment, plus the samples are not reusable. However, keeping the the nanogaps short circuited all the time means that they can be connected to a loop of metal that can be excited wirelessly to provide the electric field to the nanogap and this is what we propose to achieve in this project
Assignment Develop a wireless circuit that can excite a dielectrophoretic trap via a loop of metal on the glass chip. The task would be to develop a corresponding PCB with a wireless unit that will couple sufficiently to the receiver loop on the chip to be able to pass AC voltage in the 100kHz-10MHz range with peak-to-peak 5V at the tips of the electrodes. The transient times should be in sub-ms range, because in the nanoDEP applications the applied field can be changed dynamically to manipulate the analyte in the gap.
To read: [1] https://arxiv.org/abs/2405.12338,
[2] https://www.nature.com/articles/s41467-022-35777-2
