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ISFETs (ion sensitive field effect transistors) are ion solid-state sensors based on MOSFETs (metal oxide semiconductor field effect transistors) applied in many areas including ion imaging, detection of viruses and bacteria and DNA sequencing. ISFETs implemented in standard CMOS technology adopt the inherent Si3N4 passivation as the sensing layer, and benefit from a high integration level with no need of post-processing steps. However, this implementation is associated with non-idealities such as output temporal drift, capacitive attenuation of the input signal and random offsets in the threshold voltage due to trapped charges. Most of these non-idealities, which require better understanding, are characterized through biasing a reference electrode immersed in a solution in contact with the passivation layer. To remove electrochemical effects from the measurements, this paper proposes a dry test where the wet test setup is replaced with a sputtered gold thin film that provides electrical contact with the ISFETs. Dry tests were performed in arrays of n-ISFETs and p-ISFETs from chips fabricated in a standard 180 nm high voltage CMOS technology. The intra-die threshold voltages of the n-ISFETs and p-ISFETs presented, on average, similar offsets, but their die-to-die fluctuation was high. Wet tests on an n-ISFET and a p-ISFET of two non-metalized chips indicated sensitivities of 38 mV/pH and 46 mV/pH, respectively. The dry test introduced herein allows the electrical parameters of ISFETs to be determined without the interference of chemical contributions as well as the charges trapped in the passivation layer to be estimated.

Inkjet printing presents a high potential for cost reduction of electronic devices manufacturing due to the capacity to deposit materials with high precision, less material waste, and large-scale production through the roll-to-roll printing processes. In this work, a nanostructured TiO2 ink was developed using TiO2 aerogel and an alkaline aqueous solution, which resulted in a very stable suspension. A high-intensity ultrasonic mixer was used to fragment and disperse TiO2 aerogels producing suspensions with particles smaller than 200 nm, which are suitable for the inkjet printing process. For the development of the ink, the viscosity and surface tension were adjusted by using glycerol and a surfactant (Triton X-100). The influence of those components on the properties of the ink was evaluated for different concentrations. After formulation of the inks, the printing parameters were adjusted to optimize the process. Films with high surface area and less than 100 nm grain size were successfully produced. Electrical measurements revealed a resistive-like behavior with the sheet resistance increasing with number of printed layers.

This work reports the one-step synthesis of bacterial nanocellulose (BNC) incorporated with polypyrrole (PPy) by chemical in situ polymerization of pyrrole (Py) using CuCl2·2H2O as both oxidant agent and functional component, varying the concentration and molar ratio. Electrical, morphological, and physical-chemical properties of these nanocomposites were investigated. The results revealed that with the increase of Py concentration and molar ratio, the nanocomposites presented traces of copper chloride and copper oxide as shown by Raman and XRD analysis. The quality of bacterial cellulose nanofibers coating by the polymer and the electrical conductivity of the nanocomposites was directly affected by those variables. The combination of the conducting polymer with the oxidant agent offers possibilities for different applications such as electronic devices and sensors.