Leandro Lorenzelli

Technologies for Printing Sensors and Electronics Over Large Flexible Substrates: A Review

Printing sensors and electronics over flexible substrates are an area of significant interest due to low-cost fabrication and possibility of obtaining multifunctional electronics over large areas. Over the years, a number of printing technologies have been developed to pattern a wide range of electronic materials on diverse substrates. As further expansion of printed technologies is expected in future for sensors and electronics, it is opportune to review the common features, the complementarities, and the challenges associated with various printing technologies. This paper presents a comprehensive review of various printing technologies, commonly used substrates and electronic materials. Various solution/dry printing and contact/noncontact printing technologies have been assessed on the basis of technological, materials, and process-related developments in the field. Critical challenges in various printing techniques and potential research directions have been highlighted. Possibilities of merging various printing methodologies have been explored to extend the lab developed standalone systems to high-speed roll-to-roll production lines for system level integration.

Development of ISFET array-based microsystems for bioelectrochemical measurements of cell populations

Monitoring the bioelectrochemical activity of living cells with sensor array-based microsystems represents an emerging technique in a large area of biomedical applications, ranging from basic research to various fields of pharmacological analyses. The main appeal is the ability of these miniaturised microsystems to perform, in real time, non-invasive in-vitro investigations of the physiological state of a cell population. In this paper, we present two different microsystems designed for multisite monitoring of the physiological state of a cell population. The first microsystem, intended for cellular metabolism monitoring, consists of an array of 12 spatially distributed ISFETs to detect small pH variations induced by the cell population. The second microsystem consists of an array of 40 ISFETs and 20 gold microelectrodes and it has been designed to monitor the electrical activity of neurons. This is achieved by direct coupling of the neuronal culture with the ISFET sensitive layer and by utilising gold microelectrodes for neuronal electrical stimulation.

Piezoelectric oxide semiconductor field effect transistor touch sensing devices

This work presents piezoelectric oxide semiconductor field effect transistor (POSFET) based touch sensing devices. These devices are fabricated by spin coating thin (∼2.5 μm) piezoelectric polymer film directly on to the gate area of metal oxide semiconductor (MOS) transistor. The polymer film is processed in situ and challenging issues such as in situ poling of piezoelectric polymer film, without damaging or altering the characteristics of underlying MOS devices, are successfully dealt with. The POSFET device represents an integral “sensotronic” unit comprising of transducer and the transistor—thereby sensing as well as conditioning (and processing) the touch signal at “same site.”

Towards Tactile Sensing System on Chip for Robotic Applications

This paper presents the research on tactile sensing system on chip. The tactile sensing chips comprise of 5 × 5 array of Piezoelectric Oxide Semiconductor Field Effect Transistor (POSFET) devices and temperature sensors. The POSFET devices are obtained by spin coating piezoelectric polymer, poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), films directly on to the gate area of Metal Oxide Semiconductor (MOS) transistors. The tactile sensing chips are able to measure dynamic contact forces and temperatures. The readout and the data acquisition system to acquire the tactile signals are also presented. The chips have been extensively tested over wide range of dynamic contact forces and temperatures and the experimental results are presented. The paper also reports the research on tactile sensing chips with POSFET array and the integrated electronics.

Flexible Tactile Sensors Using Screen-Printed P(VDF-TrFE) and MWCNT/PDMS Composites

This paper presents and compares two different types of screen-printed flexible and conformable pressure sensors arrays. In both variants, the flexible pressure sensors are in the form of segmental arrays of parallel plate structure-sandwiching the piezoelectric polymer polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] between two printed metal layers of silver (Ag) in one case and the piezoresistive [multiwall carbon nanotube (MWCNT) mixed with poly(dimethylsiloxane (PDMS)] layer in the other. Each sensor module consists of 4 × 4 sensors array with 1-mm × 1-mm sensitive area of each sensor. The screen-printed piezoelectric sensors array exploits the change in polarization level of P(VDF-TrFE) to detect dynamic tactile parameter such as contact force. Similarly, the piezoresistive sensors array exploits the change in resistance of the bulk printed layer of MWCNT/PDMS composite. The two variants are compared on the basis of fabrication by printing on plastic substrate, ease of processing and handling of the materials, compatibility of the dissimilar materials in multilayers structure, adhesion, and finally according to the response to the normal compressive forces. The foldable pressure sensors arrays are completely realized using screen-printing technology and are targeted toward realizing low-cost electronic skin.

SPICE model for lossy piezoelectric polymers

Transmission line equivalent model for lossy piezoelectric polymers and its SPICE implementation are presented. The model includes the mechanical/viscoelastic, dielectric/electrical and piezoelectric/electromechanical losses, in a novel way by using complex elastic, dielectric and piezoelectric constants - obtained from measured impedance of PVDF-TrFE sample. The equivalent circuit parameters are derived from analogies between lossy electrical transmission line and acoustic wave propagation. The simulated impedance and phase plots of polymer, working in thickness mode, have been compared with measured data.

Bioelectrochemical signal monitoring of in-vitro cultured cells by means of an automated microsystem based on solid state sensor-array

In the last decade, fundamental advances in whole cell based sensors and microsystems have established the extracellular acidification rate monitoring of cell cultures as an important indicator of the global cellular metabolism. Innovative approaches adopting advanced integrated sensor array-based microsystems represent an emerging technique with numerous biomedical applications. This paper reports a cell-based microsystem, for multisite monitoring of the physiological state of cell populations. The functional components of the microsystem are an ion sensitive field effect transistor (ISFET) array-based sensor chip and a CMOS integrated circuit for signal conditioning and sensor signal multiplexing. In order to validate the microsystem capabilities for in-vitro toxicity screening applications, preliminary experimental measurements with Cheratinocytes, and CHO cells are presented. Variations in the acidification rate, imputable to the inhibitory effect of the drug on the metabolic cell activity have been monitored and cell viability during long term measurements has been also demonstrated.

New materials and advances in making electronic skin for interactive robots

Flexible electronics has huge potential to bring revolution in robotics and prosthetics as well as to bring about the next big evolution in electronics industry. In robotics and related applications, it is expected to revolutionise the way with which machines interact with humans, real-world objects and the environment. For example, the conformable electronic or tactile skin on robot’s body, enabled by advances in flexible electronics, will allow safe robotic interaction during physical contact of robot with various objects. Developing a conformable, bendable and stretchable electronic system requires distributing electronics over large non-planar surfaces and movable components. The current research focus in this direction is marked by the use of novel materials or by the smart engineering of the traditional materials to develop new sensors, electronics on substrates that can be wrapped around curved surfaces. Attempts are being made to achieve flexibility/stretchability in e-skin while retaining a reliable operation. This review provides insight into various materials that have been used in the development of flexible electronics primarily for e-skin applications.

Recent sensing technologies for pathogen detection in milk: a review.

Quality control utilising Hazard Analysis and Critical Control Points in the dairy industry generates a large volume of samples. The associated costs are significant. The development and application of fast, sensitive and cost effective analytical systems for pathogen detection in milk could aid the industry in the reduction of overheads, find new uses in dairy farming and production precision management and unlock new markets. Recent progress in pathogen sensing technologies for milk analysis, in particular nucleic acid amplification and biosensors, is reviewed here. The importance of representative samples, detection probability and Practical Detection Limit is clarified. Methods for sample pretreatment are discussed in association with the most applicable detection methods. The major findings are summarised and future perspectives are drawn to inspire new ideas in the scientific community.

Design and fabrication of posfet devices for tactile sensing

This work presents the design and fabrication of novel piezoelectric polymer-FET touch sensing devices. With thin piezoelectric polymer (PVDF-TrFE) film directly spun and processed in situ on the gate area of MOS transistor, the device can also be called as POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) touch sensing device. The integral POSFET “sensotronics” unit, comprising of transducer and the transistor, senses and conditions the signal at ‘same site’. Challenging issues like in situ poling of piezoelectric polymer film, without damaging or altering the characteristics of underlying MOS devices, have been successfully dealt with.