Metal-organic dual layer structure for stretchable interconnects

This paper reports a novel method for obtaining stretchable interconnects using gold and organic material (PEDOT:PSS) in a dual-layer structure on PDMS substrate. With an appropriate design and carefully carried out microfabrication steps, the structure was successfully patterned into serpentine shape and highly stretchable interconnects were obtained. The fabricated interconnects can be stretched up to 170% of their original length while retaining an adequate level of conductivity

Towards Graphene Based Flexible Force Sensor

Monolayer graphene transferred over flexible polyvinyl chloride (PVC) substrate combined with closely packed layer of nano-spheres (NSs) is fabricated for force sensing application. The force was applied from vertical direction through NSs which acts as lateral strain enhancers. The stack persuades lateral in-plane strain in the monolayer graphene for the applied vertical pressure through NSs. The electrical measurements demonstrate that the graphene layer is able to respond for soft touch range commonly perceived by human beings. The sensing stack was fabricated using simple approaches such as hot lamination graphene transfer process and drop casting of NSs. The device structure is flexible to conformably cover the nonplanar surface for applications such as large area pressure sensing and robotic e-skin

POSFET tactile sensing arrays using CMOS technology

This work presents fabrication and evaluation of novel POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices based tactile sensing chip. In the newer version presented here, the tactile sensing chip has been fabricated using CMOS (Complementary Metal Oxide Semiconductor) technology. The chip consists of 4 x 4 POSFET touch sensing devices (or taxels) and both, the individual taxels and the array are designed to match spatio–temporal performance of the human fingertips. To detect contact events, the taxels utilize the contact forces induced change in the polarization level of piezoelectric polymer (and hence change in the induced channel current of MOS). The POSFET device on the chip have linear response in the tested dynamic contact forces range of 0.01–3 N and the sensitivity (without amplification) is 102.4 mV/N

Hybrid Structure of Stretchable Interconnect for Reliable E-skin Application

This paper presents the methodology for realisation of stretchable interconnects based on hybrid thin film stack of spray-coated conductive polymer PEDOT: PSS and evaporated gold (Au) film. The PEDOT: PSS film, with its properties in electrical conductivity and mechanical softness, serves as a stress release buffer in the layered hybrid structure. With the serpentine-shape design, the stretchable interconnects can accommodate larger deformation in comparison with a straight line. The correlation between interconnects' morphology (i.e. cracks propagation) with their electrical behaviour has been studied through microscope in along with electrical characterisation under external strain. Furthermore, a comparison in failure strain among different serpentine-shaped designs has been studied. Higher level in stretchability of interconnects can be achieved with a larger arc degree in design. The fabricated stretchable interconnects can accommodate significant deformations up to 72% external strain while maintaining electrically conductive

Large Area Electronic Skin

Technological advances have enabled various approaches for developing artificial organs such as bionic eyes, artificial ears, and lungs etc. Recently electronics (e-skin) or tactile skin has attracted increasing attention for its potential to detect subtle pressure changes, which may open up applications including real-time health monitoring, minimally invasive surgery, and prosthetics. The development of e-skin is challenging as, unlike other artificial organs, tactile skin has large number of different types of sensors, which are distributed over large areas and generate large amount of data. On top of this, the attributes such as softness, stretchability, and bendability etc., are difficult to be achieved as today's electronics technology is meant for electronics on planar and stiff substrates such as silicon wafers. This said, many advances, pursued through “More than Moore” technology, have recently raised hope as some of these relate to flexible electronics and have been targeted towards developing e-skin. Depending on the technology and application, the scale of e-skin could vary from small patch (e.g. for health monitoring) to large area skin (e.g. for robotics). This invited paper presents some of the advances in large area e-skin and flexible electronics, particularly related to robotics

Device Modelling of Silicon Based High-Performance Flexible Electronics

The area of flexible electronics is rapidly expanding and evolving. With applications requiring high speed and performance, ultra-thin silicon-based electronics has shown its prominence. However, the change in device response upon bending is a major concern. In absence of suitable analytical and design tool friendly model, the behavior under bent condition is hard to predict. This poses challenges to circuit designer working in the bendable electronics field, in laying out a design that can give a precise response in a stressed condition. This paper presents advances in this direction and investigates the effect of compressive and tensile stress on the performance of NMOS and PMOS transistor and a touch sensor comprising a transistor and piezoelectric capacitor

Tactile feedback display with spatial and temporal resolutions.

We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications

3D Printed Interconnects on Bendable Substrates for 3D Circuits

3D printing systems are expanding to realising fully embedded, multi-purpose, out-of-plane circuits. It is possible to utilise the characteristics of 3D printing to produce customisable, complex and bendable 3D structures and sensors that go beyond the use of standard polymer materials used with the current technology. With multi-material 3D printing, the additive manufacturing could be advanced to produce fully embedded sensors and electronic systems that cannot be otherwise produced in a one-step automated process. Our goals are concentrated towards embedding sensing circuits into next generation prosthetics and robotic arms for more advanced and smoother operation. These devices, along with other similar interests such as healthcare wearable devices, will inevitably include moving parts. Therefore, the embedded printed connections and readout circuits should withstand the repeatable bending of the robotic phalanges or sensing devices without degrading in performance or showing any cracks