Memristive sensors for pH measure in dry conditions

Abstract

Keywords:Memristive sensor Silicon nanowires pH sensing Hysteresis Measurements in air Conductivity in thin water film A large progress in pH sensing with nanowire based ion-sensitive field-effect transistors (ISFETs) has been demonstrated over the years. The electrochemical reactions occurring at the wire surface-to-electrolyte interface play a key role in the detection of ions. In this letter, we show that pH sensing can also be performed on dried samples, through electrical measurements in air with a new kind of memristive sensor. The detection of different concentrations of [H + ] is confirmed by both the increased conductance and hysteretic voltage gap of the wires. The observed change in the electrical properties with pH in dry conditions is related to the formation of a wet film at the nanowire surface. Ions from the initial solution are free to move in the final water thin film at the sensing interface with consequent polarization of the NW surface.

Novel readout circuit for memristive biosensors in cancer detection

“…1b shows the occurring femtomolar detection of VEGF antigen: the voltage gap decreases as function of increasing uptaken VEGF molecules. The result has been confirmed also in the detection of rabbit antigen molecules [4] and pH sensing [7].…”

SiNW-FET in-Air Biosensors for High Sensitive and Specific Detection in Breast Tumor Extract

“…These preliminary experiments were essential to understand the sensitivity of our biosensors and confirm the detection improvements achieved by performing the measurements in air after the incubation of the sensor in the target solution, the washing and drying steps [6]. Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis, highly active in tumor and in vascular diseases [13].…”

“…First, we demonstrate that the fabricated high quality SiNW-FET based sensors achieve the detection of VEGF-A (Vascular Endothelial Growth Factor) femto-moles when diluted in a controlled physiological environment (Phosphate Buffered Saline, PBS). The measurements are carried out in air after sensor incubation in PBS solution containing the cancer markers, thus enabling higher sensitivity thanks to the increased Debye screening length of the thin liquid film formed at the interface [6], with respect to the one of bulk liquid in standard biosensing systems. We then show that with the same devices and improved specificity we detected low concentrated antigen molecules in a real tumor landscape.…”

Reliable redundancy with memristive-biosensors to achieve statistical significance in immunosensing

“…Changes of the hysteretic voltage gap of the sensor were monitored prior to and after antibody functionalization, and then after exposure of the sensor to the antigen. All the acquisitions were performed under controlled conditions: at the relative humidity (rH) of 50% and a temperature of 21 C. The proposed improved sensitivity in dry condition [20], [21] was ensured by an increased Debye length deriving from the absence of counterions from the bulk electrolytic solution [22].…”