A Biosensor-CMOS Platform and Integrated Readout Circuit in 0.18-μm CMOS Technology for Cancer Biomarker Detection

This paper presents a biosensor-CMOS platform for measuring the capacitive coupling of biorecognition elements. The biosensor is designed, fabricated, and tested for the detection and quantification of a protein that reveals the presence of early-stage cancer. For the first time, the spermidine/spermine N1 acetyltransferase (SSAT) enzyme has been screened and quantified on the surface of a capacitive sensor. The sensor surface is treated to immobilize antibodies, and the baseline capacitance of the biosensor is reduced by connecting an array of capacitors in series for fixed exposure area to the analyte. A large sensing area with small baseline capacitance is implemented to achieve a high sensitivity to SSAT enzyme concentrations. The sensed capacitance value is digitized by using a 12-bit highly digital successive-approximation capacitance-to-digital converter that is implemented in a 0.18 μm CMOS technology. The readout circuit operates in the near-subthreshold regime and provides power and area efficient operation. The capacitance range is 16.137 pF with a 4.5 fF absolute resolution, which adequately covers the concentrations of 10 mg/L, 5 mg/L, 2.5 mg/L, and 1.25 mg/L of the SSAT enzyme. The concentrations were selected as a pilot study, and the platform was shown to demonstrate high sensitivity for SSAT enzymes on the surface of the capacitive sensor. The tested prototype demonstrated 42.5 μS of measurement time and a total power consumption of 2.1 μW

A Biosensor-CMOS Platform and Integrated Readout Circuit in 0.18-μm CMOS Technology for Cancer Biomarker Detection

This paper presents a biosensor-CMOS platform for measuring the capacitive coupling of biorecognition elements. The biosensor is designed, fabricated, and tested for the detection and quantification of a protein that reveals the presence of early-stage cancer. For the first time, the spermidine/spermine N1 acetyltransferase (SSAT) enzyme has been screened and quantified on the surface of a capacitive sensor. The sensor surface is treated to immobilize antibodies, and the baseline capacitance of the biosensor is reduced by connecting an array of capacitors in series for fixed exposure area to the analyte. A large sensing area with small baseline capacitance is implemented to achieve a high sensitivity to SSAT enzyme concentrations. The sensed capacitance value is digitized by using a 12-bit highly digital successive-approximation capacitance-to-digital converter that is implemented in a 0.18 μm CMOS technology. The readout circuit operates in the near-subthreshold regime and provides power and area efficient operation. The capacitance range is 16.137 pF with a 4.5 fF absolute resolution, which adequately covers the concentrations of 10 mg/L, 5 mg/L, 2.5 mg/L, and 1.25 mg/L of the SSAT enzyme. The concentrations were selected as a pilot study, and the platform was shown to demonstrate high sensitivity for SSAT enzymes on the surface of the capacitive sensor. The tested prototype demonstrated 42.5 μS of measurement time and a total power consumption of 2.1 μW

High-performance flexible magnetic tunnel junctions for smart miniaturized instruments

Flexible electronics is an emerging field in many applications ranging from in vivo biomedical devices to wearable smart systems. the capability of conforming to curved surfaces opens the door to add electronic components to miniaturized instruments, where size and weight are critical parameters. given their prevalence on the sensors market, flexible magnetic sensors play a major role in this progress. for many high-performance applications, magnetic tunnel junctions (mtjs) have become the first choice, due to their high sensitivity, low power consumption etc. mtjs are also promising candidates for non-volatile next-generation data storage media and, hence, could become central components of wearable electronic devices. in this work, a generic low-cost regenerative batch fabrication process is utilized to transform rigid mtjs on a 500 mu m silicon wafer substrate into 5 mu m thin, mechanically flexible silicon devices, and ensuring optimal utilization of the whole substrate. this method maintains the outstanding magnetic properties, which are only obtained by deposition of the mtj on smooth high-quality silicon wafers. the flexible mtjs are highly reliable and resistive to mechanical stress. bending of the mtj stacks with a diameter as small as 500 mu m is possible without compromising their performance and an endurance of over 1000 cycles without fatigue has been demonstrated. the flexible mtjs are mounted onto the tip of a cardiac catheter with 2mm in diameter without compromising their performance. this enables the detection of magnetic fields and the angle which they are applied at with a high sensitivity of 4.93%/oe and a low power consumption of 0.15w, while adding only 8 and 5m to the weight and diameter of the catheter, respectively