A CMOS Multi-Electrode Array for Four-Electrode Bioimpedance Measurements

Abstract

This work demonstrates how a multielectrode array (MEA) dedicated to four-electrode bioimpedance measurements can be implemented on a complementary metal-oxide-semiconductor (CMOS) chip. As a proof of concept, an 8x8 pixel array along with dedicated amplifiers was designed and fabricated in the TSMC 180 nm process. Each pixel in the array contains a circular current carrying (CC) electrode that can act as a current source or sink. In order to measure a differential voltage between the pixels, each CC electrode is surrounded by a ring shaped pick up (PU) electrode. The differential voltages can be measured by an onboard instrumentation amplifier, while the currents can be measured with an on-bard transimpedance amplifier. Openings in the passivation layer exposed the aluminum top metal layer, and a metal stack of zinc, nickel and gold was deposited in an electroless plating process. The chips were then wire bonded to a ceramic package and prepared for wet experiments by encapsulating the bonding wires and pads in the photoresist SU-8. Measurements in liquids with different conductivities were performed to demonstrate the functionality of the chip.

Development of a Tetherless Bioimpedance Device That Uses Morphologic Changes to Predict Blood Flow Restrictions Mimicking Peripheral Artery Disease Progression

“…The results presented in Figure 6 demonstrate the outcomes of the HFSS simulations conducted to guide the modulation frequency selection and the placement of the bioimpedance electrodes to maximize the amount of signal entering and coming from the artery rather than the non-arterial tissue as well as to assess the effect of misalignment of the electrodes relative to the artery. In Figure 6 a, the simulation setup includes the model with four electrodes: two current injection probes and two voltage detection probes [ 65 , 66 , 67 ]. The model also incorporates layers representing the epidermis, dermis, artery, and blood.…”