A CMOS-based electrochemical bio molecule detection microarray
[article]
Anouar Laifi, Technische Universität Berlin, Roland Thewes
2021
This work presents an electrochemical DNA sensor microarray which supports the detection principles cyclic voltammetry (CV) and Coulometry. The three-electrode system needed for these detection methods is post-processed on the solid-state 5.5 mm x 3 mm CMOS-based chip, which is realized in a 180 nm, 1.8 V and 3.3 V standard CMOS technology. The constellation of an array of 109 working electrodes surrounded by the counter electrode and the reference electrodes is designed to meet stability
more »
... ements and structured using layers of gold and silicon nitride. The DNA sensor chip presented in this work has 3 operation modes: a calibration mode, a cleaning mode, and a measurement mode. Every single pixel has an area of 120 µm x 120 µm and consists of one working electrode connected to a readout CMOS circuitry: a 1-bit first order continuous-time ?S modulator. When its reference voltage is varied, the modulator measures its input current while controlling the electrode potential as required for cyclic voltammetry. With a sampling frequency of 10 MHz and an oversampling of 512, the pixel output data rate is around 20 ksamples/s. It allows a maximum input current amplitude of 15.6 nA. Post-layout simulations including transient device noise predict SNR of 63.4 dB and a SNDR of 62.9 dB. The modulator reference voltage is generated by an 8-bit segmented DAC with a full-scale range of 0.63 V. Simulations prove DAC monotonicity with worst-case DNL value of 0.783 LSB. The potentiostat controlling the electrolyte potential is realized as a super class AB amplifier with a peak supply current of 6.5 mA and a quiescent supply current of 0.5 mA. The potentiostat is controlled by an 8-bit segmented DAC with a full-scale output voltage range of 1.39 V. The potentiostat together with its driving DAC achieves voltage steps of ±1 V in 1 µs. Biasing circuits, calibration current sources, bandgap reference, and POR-circuits are designed and implemented on-chip. Thanks to these circuits, the number of chip pads is reduced to 6. A part of [...]
doi:10.14279/depositonce-11233
fatcat:yprio2iev5djdh5xbu4yscj7du