Ultra-thin silicon based piezoelectric capacitive tactile sensor

This paper presents an ultra-thin bendable silicon based tactile sensor, in a piezoelectric capacitor configuration, realized by wet anisotropic etching as post-processing steps. The device is fabricated over bulk silicon, which is thinned down to 35 μm from an original thickness of 636 μm. Dicing of thin membrane is achieved by low cost novel technique of Dicing before Etching. The piezoelectric capacitor is composed of polyvinylidene fluoride trifluoroethylene (PVDF-TrFE), which present an attractive avenue for tactile sensing as they respond to dynamic contact events (which is critical for robotic tasks), easy to fabricate at low cost and are inherently flexible. The sensor exhibits enhanced piezoelectric properties, thanks to the optimization of the poling procedure. The sensor capacitive behaviour is confirmed using impedance analysis and the electro-mechanical characterization is done using TIRA shaker setup

Capacitive coupled RFID tag using a new dielectric droplet encapsulation approach

Radio frequency identification (RFID) is a well-known and fast-growing technology used to identify people, animals and products. RFID tags are used to replace bar codes in a wide range of applications, to mention just a few, retail, transportation, logistics and healthcare. The two main driving aspects for most of research and development projects concerning RFID tags are the reduction of assembly costs and the downsizing of microchips. In that respect and considering an Industry 4.0 scenario, the study of a new assembly approach for passive and high frequency RFID tags has been proposed and studied in this thesis. In this new approach, which is based on the inkjet printing technology, a specifically designed radio frequency integrated circuit (RFIC) will be delivered, inside a liquid dielectric droplet, onto the antenna and no longer placed and oriented precisely as it happens nowadays with pick-and-place and flip chip machines. After a landing phase, the liquid droplet (with the encapsulated chip) will self-aligns with respect to the contact thanks to capillary forces driven by specifically designed wetting conditions on the substrate of the antenna. Finally, with few additional steps, the complete RFID tag is created. This research project brings to light a considerable simplification and a very high potential of parallelization, compatible with large volume manufacturing methods, in comparison to nowadays existing technologies. This may substantially drive down the fabrication costs. An in-depth analysis of electrical performances have been carefully undertaken and compliance with the ISO/IEC 144443 standard has been verified. Mathematical models have been developed showing fundamental limits for the maximum tag reading range and power requirements of the RFID reader

Towards Single-Chip Nano-Systems

Important scientific discoveries are being propelled by the advent of nano-scale sensors that capture weak signals from their environment and pass them to complex instrumentation interface circuits for signal detection and processing. The highlight of this research is to investigate fabrication technologies to integrate such precision equipment with nano-sensors on a single complementary metal oxide semiconductor (CMOS) chip. In this context, several demonstration vehicles are proposed. First, an integration technology suitable for a fully integrated flexible microelectrode array has been proposed. A microelectrode array containing a single temperature sensor has been characterized and the versatility under dry/wet, and relaxed/strained conditions has been verified. On-chip instrumentation amplifier has been utilized to improve the temperature sensitivity of the device. While the flexibility of the array has been confirmed by laminating it on a fixed single cell, future experiments are necessary to confirm application of this device for live cell and tissue measurements. The proposed array can potentially attach itself to the pulsating surface of a single living cell or a network of cells to detect their vital signs

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

The effect of bending on laser-cut electro-textile inductors and capacitors attached on denim as wearable structures

In this paper we present the design, fabrication and characterization of electro-textile inductor and capacitor patterns on denim fabric as a basis for the development of wearable e-textiles. Planar coil inductors have been harnessed as antenna structures for the development of Near Field Communication (NFC) tags with temperature sensing capability, while interdigitated electrode (IDE) capacitors have been used as humidity sensors for wearable applications. The effect of bending in the electrical performance of such structures was evaluated, showing variations below 5% in both inductance and capacitance values for bending angles in the range of interest, i.e. those fitting to human limbs. In the case of the fabricated NFC tags, a shift in the resonance frequency below 1.7% was found, meaning that the e-textile tag would still be readable by an NFC- enabled smartphone. In respect of the capacitive humidity sensor, we obtained a minimum capacitance variation of 40% for a relative humidity range from 10% to 90%. Measured thermal shift was below 5% in the range from 10 to 40oC. When compared to the 4% variation due to bending, it can be concluded that this capacitive structure can be harnessed as humidity sensor even under bending strain conditions and moderate temperature variations. The development and characterization of such structures on denim fabrics, which is one of the most popular fabrics for everyday clothing, combined with the additional advantage of affordable and easy fabrication methodologies, means a further step towards the next generation of smart e-textile products

Inkjet printed paper based frequency selective surfaces and skin mounted RFID tags: the interrelation between silver nanoparticle ink, paper substrate and low temperature sintering technique

Inkjet printing of functional frequency selective surfaces (FSS) and radio frequency identification (RFID) tags on commercial paper substrates using silver nanoparticle inks sintered using low temperature thermal, plasma and photonic techniques is reported. Printed and sintered FSS devices demonstrate performances which achieve wireless communication requirements having a forward transmission scattering parameter, S21, depth greater than ?20 dB at 13 GHz. Printed and plasma sintered RFID tags on transfer paper, which are capable of being mounted on skin, improved read distances compared to previously reported single layer transfer RFID tags fabricated by conventional thermal sintering

Technological Integration in Printed Electronics

Conventional electronics requires the use of numerous deposition techniques (e.g. chemical vapor deposition, physical vapor deposition, and photolithography) with demanding conditions like ultra-high vacuum, elevated temperature and clean room facilities. In the last decades, printed electronics (PE) has proved the use of standard printing techniques to develop electronic devices with new features such as, large area fabrication, mechanical flexibility, environmental friendliness and—potentially—cost effectiveness. This kind of devices is especially interesting for the popular concept of the Internet of Things (IoT), in which the number of employed electronic devices increases massively. Because of this trend, the cost and environmental impact are gradually becoming a substantial issue. One of the main technological barriers to overcome for PE to be a real competitor in this context, however, is the integration of these non-conventional techniques between each other and the embedding of these devices in standard electronics. This chapter summarizes the advances made in this direction, focusing on the use of different techniques in one process flow and the integration of printed electronics with conventional systems