Massimo Barbaro

A charge-modulated FET for detection of biomolecular processes: conception, modeling, and simulation

A novel, solid-state sensor for charge detection in biomolecular processes is proposed. The device, called charge-modulated field-effect transistor, is compatible with a standard CMOS process, thus allowing fully electronic readout and large scale of integration of biosensors on a single chip. The detection mechanism is based on the field-effect modulation induced by electric charge changes related to the bioprocess. A model of the device was developed, to provide a manageable relationship between its output and geometric, design and process parameters. Extensive two- and three-dimensional simulations of the proposed structure validated the model and the working principle.

A CMOS, fully integrated sensor for electronic detection of DNA hybridization

An integrated field-effect device for fully electronic deoxyribonucleic acid (DNA) detection was realized in a standard CMOS process. The device is composed of a floating-gate MOS transistor, a control-capacitor acting as integrated counterelectrode, and an exposed active area for DNA immobilization. The drain-current of the transistor is modulated by the electric charge carried by the DNA molecules. After DNA hybridization, this charge increases and a change in the output current is measured. Experimental results are provided. Full compatibility with a standard CMOS process opens the way to the realization of low-cost large-scale integration of fast electronic DNA detectors.

Ultralow Voltage, OTFT‐Based Sensor for Label‐Free DNA Detection

An organic ultralow voltage field effect transistor for DNA hybridization detection is presented. The transduction mechanism is based on a field-effect modulation due to the electrical charge of the oligonucleotides, so label-free detection can be performed. The device shows a sub-nanometer detection limit and unprecedented selectivity with respect to single nucleotide polymorphism.

Ultra-low voltage, organic thin film transistors fabricated on plastic substrates by a highly reproducible process

Organic thin film transistors have been fabricated on plastic substrates using a combination of two ultrathin insulating films, namely a 6 nm Al2O3 film (grown by UV-Ozone treatment of a pre-deposited aluminium film) and a 25 nm parylene C film deposited by vapour phase, as gate dielectric. They show a very low leakage current density, around 2 × 10−9 A/cm2, and, most importantly, can be operated at voltages below 1 V. We demonstrate that this low-cost technique is highly reproducible and represents a step forward for the routine fabrication of ultra-low voltage plastic electronics.

Active Devices Based on Organic Semiconductors for Wearable Applications

Plastic electronics is an enabling technology for obtaining active (transistor based) electronic circuits on flexible and/or nonplanar surfaces. For these reasons, it appears as a perfect candidate to promote future developments of wearable electronics toward the concept of fabrics and garments made by functional (in this case, active electronic) yarns. In this paper, a panoramic view of recent achievements and future perspectives is given.

Peripheral Neural Activity Recording and Stimulation System

This paper presents a portable, embedded, microcontroller-based system for bidirectional communication (recording and stimulation) between an electrode, implanted in the peripheral nervous system, and a host computer. The device is able to record and digitize spontaneous and/or evoked neural activities and store them in data files on a PC. In addition, the system has the capability of providing electrical stimulation of peripheral nerves, injecting biphasic current pulses with programmable duration, intensity, and frequency. The recording system provides a highly selective band-pass filter from 800 Hz to 3 kHz, with a gain of 56 dB. The amplification range can be further extended to 96 dB with a variable gain amplifier. The proposed acquisition/stimulation circuitry has been successfully tested through in vivo measurements, implanting a tf-LIFE electrode in the sciatic nerve of a rat. Once implanted, the device showed an input referred noise of 0.83 μVrms, was capable of recording signals below 10 μ V, and generated muscle responses to injected stimuli. The results demonstrate the capability of processing and transmitting neural signals with very low distortion and with a power consumption lower than 1 W. A graphic, user-friendly interface has been developed to facilitate the configuration of the entire system, providing the possibility to activate stimulation and monitor recordings in real time.

Organic-based sensor for chemical detection in aqueous solution

We present a flexible, pentacene-based field-effect device, for the detection of chemical species in aqueous solution. The sensor consists in a double-gate transistor, where the detection is achieved by exploiting the charge sensing capabilities of the floating-gate terminal. To provide the pH-sensitivity, the floating gate is functionalized with thioamine groups as such groups protonize proportionally to the concentration of H3O+ ions in solution. With respect to the existing organic-based devices for pH monitoring, our sensor does not require a counterelectrode and the organic semiconductor is not affected by the contact with the monitored solution.

Area and Power Modeling for Networks-on-Chip with Layout Awareness

Networks-on-Chip (NoCs) are emerging as scalable interconnection architectures, designed to support the increasing amount of cores that are integrated onto a silicon die. Compared to traditional interconnects, however, NoCs still lack well established CAD deployment tools to tackle the large amount of available degrees of freedom, starting from the choice of a network topology. “Silicon-aware” optimization tools are now emerging in literature; they select an NoC topology taking into account the tradeoff between performance and hardware cost, that is, area and power consumption. A key requirement for the effectiveness of these tools, however, is the availability of accurate analytical models for power and area. Such models are unfortunately not as available and well understood as those for traditional communication fabrics. Further, simplistic models may turn out to be totally inaccurate when applied to wire dominated architectures; this observation demands at least for a model validation step against placed and routed devices. In this work, given an NoC reference architecture, we present a flow to devise analytical models of area occupation and power consumption of NoC switches, and propose strategies for coefficient characterization which have different tradeoffs in terms of accuracy and of modeling activity effort. The models are parameterized on several architectural, synthesis-related, and traffic variables, resulting in maximum flexibility. We finally assess the accuracy of the models, checking whether they can also be applied to placed and routed NoC blocks.

Flexible Organic Thin-Film Transistors for pH Monitoring

A novel freestanding flexible device based on an organic field effect transistor (OFET), able to detect pH changes in chemical solutions thanks to a functionalized floating-gate, was realized and successfully tested. The device is assembled on a flexible film (Mylar), which acts at the same time as gate insulator and as mechanical support for the whole structure. On one side of the foil a control gate and drain/source contacts are photolithographically patterned, and a pentacene active layer deposited; on the opposite side a gold floating gate is defined. The sensor performs the detection of the chemical species placed over the probe area by detecting the associated electric charge: the structure, basically, works as a floating-gate transistor whose threshold voltage is modulated by the surface charge due to the solution under investigation. By properly functionalizing the floating gate surface, sensitivity to different species and the detection of different reactions can be achieved, with the same sensor. In this work we present its application as ion-sensitive device. pH sensitivity is achieved by functionalizing the sensing surface with thio-aminic groups as such groups protonate proportionally to the concentration of H3O+ ions in the solution. Such a structure does not require a counter-electrode as the OFET is biased through a control gate. Moreover, the working mechanism is independent of the choice of semiconductor, gate or dielectric material, since the OFET is insulated from the solution. The application as DNA sensor is currently under investigation as well.

Ultralow Voltage Pressure Sensors Based on Organic FETs and Compressible Capacitors

A novel structure for the fabrication of organic pressure sensors is presented. It is based on a polydimethylsiloxane capacitor integrated with a floating-gate organic field-effect transistor (OFET) able to operate at ultralow voltages. The thin-film device, fabricated on a flexible substrate, is specifically conceived for tactile sensing. The main novelty of the working principle consists in the physical separation between the pressure-sensitive area and the active area of the OFET. The complete characterization of the device, in response to the application of different pressures, is provided.