Low cost CMOS-MEMS platforms for biosensing applications (REMEDI)
The main goal of the project is the development of compact and low cost CMOS-MEMS platforms for bio-sensing applications based on the adoption of microelectromechanical resonators (MEMS) as the sensing element integrated monolithically with CMOS circuits. This approach would attain high-sensitive CMOS-MEMS oscillator circuits enabling the sensor continuous tracking through the quasi-digital output signal provided. Based on our previous experience we are aimed to exploit commercial and mature submicrometer-scale CMOS technologies to develop such devices providing both high-performance and low cost. The proposal envisages the development of CMOS-MEMS sensor devices based on two operation principles: i) thermal biosensing, or biocalorimeters, based on the use of high-sensitivity MEMS resonators with temperature, and ii) gravimetric biosensing of volatile organic compounds (VOC) using extreme mass sensitive MEMS resonators. Although having dissimilar operating principles their implementation and development through resonant CMOS-MEMS oscillators is technologically compatible. In both cases the sensing element is a MEMS resonator with electrostatic actuation and capacitive readout that will allow its full integration within standard CMOS ICs. We plan to develop various prototypes for each approach considering at least two submicrometer CMOS technological nodes with the goal of surpassing the state-of-the-art sensitivities. Moreover, the planned multidisciplinary collaborations are aimed at providing a final application, as there will be efforts to integrate the microfluidic channels together with the thermal sensors that could provide sensitivity at the cellular level. Similarly a newly developed specific coating technique for the mass sensors targeting specifically the CMOS metal layers will be experienced to measurement VOC acetone concentration as an indirect determination for the glucose levels in plasma.
IEEE SENSORS Journal, Vol. 23, No. 1, Jan 2023.
Abstract—Volatile organic compounds (VOCs) have gained the biomedical community’s attention given their relevance in exhaled human breath analysis for noninvasive disease diagnosis. Today, only bulky, expensive, and high-skill bench-top equipment is commercially available to reach the outstanding resolution and selectivity required for their detection. However, these solutions fail to meet the society demands of portable and low-cost devices required for point-of-care diagnosis and e-health. In this line, resonant inertial mass sensing has emerged as a promising technique to achieve high-resolution VOCs’ identification, fulfilling the portability requirements. Their excellent distributed mass sensitivity and integration capabilities within standard CMOS microfabrication techniques constitute excellent candidates for building lab-on-chip applications in line with current technological trends. The capability of operating as self-sustained oscillators provides an inherent real-time tracking system with quasi-digital output. Resonator coating using novel sensing films for specific analyte caption is required to boost themass loading effect and improve sensing selectivity. This article reviews and analyzes the resonator topologies proposed in the literature together with the echniques used for electromechanical transduction, as well as coating materials and procedures. The ultimate goal is to discuss the advantages achieved for CMOS fully integrated solutions, analyzing the state of the art in the field and providing specific design guidelines while foreseeing upcoming trends.
CMOS-MEMS resonators have become a promising solution thanks to their miniaturization and on-chip integration capabilities. However, using a CMOS technology to fabricate microelectromechanical system (MEMS) devices limits the electromechanical performance otherwise achieved by specific technologies, requiring a challenging readout circuitry. This paper presents a transimpedance amplifier (TIA) fabricated using a commercial 0.35-m CMOS technology specifically oriented to drive and sense monolithically integrated CMOS-MEMS resonators up to 50 MHz with a tunable transimpedance gain ranging from 112 dB to 121 dB. The output voltage noise is as low as 225 nV/Hz1/2—input-referred current noise of 192 fA/Hz1/2—at 10 MHz, and the power consumption is kept below 1-mW. In addition, the TIA amplifier exhibits an open-loop gain independent of the parasitic input capacitance—mostly associated with the MEMS layout—representing an advantage in MEMS testing compared to other alternatives such as Pierce oscillator schemes. The work presented includes the characterization of three types of MEMS resonators that have been fabricated and experimentally characterized both in open-loop and self-sustained configurations using the integrated TIA amplifier. The experimental characterization includes an accurate extraction of the electromechanical parameters for the three fabricated structures that enables an accurate MEMS-CMOS circuitry co-design.