Nanoelectrode array biosensors - programmable non-overlapping clocks generator project
High-frequency impedance spectroscopy nanobiosensors have been used to detect and characterize a variety of analytes in electrolyte (e.g., microbeads, cells, viruses, proteins). In fact, thanks to their small size, nanoscale sensors enable to perform single-particle detection, and massively parallel nanoelectrode array implementations are well suited for achieving high spatial resolutions. However, in order to overcome the screening of the signals caused by the electrical double layer (ions accumulating on the electrode's surface), high-frequencies of operation are required [1-3].
Charge-based capacitance measurements (CBCM) are a popular sensing approach to achieve high frequencies of operation. In a nutshell, the principle of operation consists in alternatively charging/discharging a nanoelectrode with two switches, and integrating the resulting average charging current to estimate the transferred charge, and ultimately the capacitance. To achieve this goal, programmable non-overlapping clocks are required to properly actuate the switches.
Within this framework, we consider the biochip described in [1-3]. The chip is mounted on a PCB adaptor (see picture), that provides all the connectivity for the digital/slow control signals (via a flat-cable connector), and for high-speed non-overlapping clocks. This project aims at designing a board for the generation of these programmable non-overlapping clocks, to actuate the CBCM switches of the biochip. This requires the design of an analog/mixed-signal board that generates non-overlapping clocks with programmable amplitudes (-0.2 V to 1.5 V, with 10 mV resolution) and rise/fall times as fast as 70 ps. Minimization of capacitive loads and proper impedance control will thus play a critical role. The board will have to guarantee proper signal quality over the whole bandwidth (7 GHz), and must satisfy electrical constraints to be properly be intergated with the existing system.
The main goal of the project is to design a board for generating programmable non-overlapping clocks, to enable the integration with the high-speed biosocket adaptor (see picture) that hosts the nanoelectrode array biochips. Starting from an existing tentative design, the project will consist in performing the PCB layout and assessing its performance. In terms of performance requirements, the non-overlapping clocks will have programmable amplitude (-0.2 V to 1.5 V, resolution 10 mV), rise/fall-times (minimum transition times to be achieved: 100 ps), repetition frequency (1 MHz to 300 MHz) and duty cycle (20% to 50%, in 5% steps).
Your tasks are
- Layouting a PCB for the generation of programmable non-overlapping clocks that exploits different circuit approaches
- Verifying the signal-integrity of the layout by means of electromagnetic simulations
- Firmware design and implementation in STM32 microcontroller to program the board's main ICs (clock generators, delay lines)
- Testing the performance of the design on different capacitive loads
- Looking for Semester Students
- PCB design course
- Microcontroller programming experience is a plus but not required
- 50% PCB design
- 10% Simulations
- 10% Microcontroller design
- 30% Programming and Testing
The references can be accessed free of charge within the ETHZ network.
 F. Widdershoven et al.: A CMOS Pixelated Nanocapacitor Biosensor Platform for High-Frequency Impedance Spectroscopy and Imaging
 S. G. Lemay et al.: High-Frequency Nanocapacitor Arrays: Concept, Recent Developments, and Outlook
 C. Laborde et al.: Real-time imaging of microparticles and living cells with CMOS nanocapacitor arrays