This project has developed two integrated microsystems fabricated in a 0.35-µm two-poly four-metal RF CMOS process for miniaturized broadband dielectric spectroscopy. In particular, first, a broadband sensor interface IC as part of a miniaturized measurement platform for MHz-to-GHz dielectric spectroscopy has been developed. The IC measures frequency-dependent S21 magnitude and phase of a microfluidic dielectric sensor fabricated in a thick gold-on-glass microfabrication process and loaded with a material-under-test (MUT). The sensor interfaced with the IC is fully capable of differentiating among deionized (DI) water, phosphate buffered saline (PBS), ethanol and methanol in tests conducted at four different excitation frequencies of 50 MHz, 500 MHz, 1 GHz and 3 GHz. Further, dielectric readings of ethanol from the sensor interfaced with the IC at five excitation frequencies in the range of 50 MHz to 2 GHz are in excellent agreement (error < 1%) with those from using a vector network analyzer (VNA) as the sensor readout.
Next, a self-sustained, miniaturized, microfluidic-CMOS platform for palmtop dielectric spectroscopy has been developed. The platform incorporates a parallel-plate capacitive sensor with a three-dimensional gap, floating electrode, and microfluidic channel for sample delivery, as well as a fully integrated transceiver for broadband dielectric spectroscopy. The IC applies a single-tone sinusoidal RF excitation signal in a frequency range of ~ 9MHz to 2.433GHz to the MUT-loaded sensor, and measures the sensor transmission characteristics in the voltage domain via an amplitude/phase measurement utilizing broadband frequency response analysis (bFRA) to extract the MUT complex permittivity with microliter sample volumes. Complex dielectric readings of PBS from the platform at six excitation frequencies in the range of 50 MHz to 2.4 GHz are in excellent agreement (RMS error <1.5% for 0.5 to 2.4 GHz) with those from a reference measurement by an Agilent 85070E dielectric probe kit interfaced with a VNA.
Finally, an autonomous self-sustained palmtop platform, incorporating the microfluidic-CMOS platform, ADC, power supply unit, Wi-Fi module, and a Raspberry Pi computing module has been developed. The palmtop platform is capable of accurately measuring the real and imaginary parts of MUT complex permittivity from ~ 9MHz to 2.433GHz in less than 5s, enabling rapid, high-throughput, and low-cost measurements with a self-sustained, portable platform that can pave the way for translating dielectric spectroscopy from the lab bench to the field or the bedside.