Towards flexible asymmetric MSM structures using Si microwires through contact printing

This paper presents development of flexible metal-semiconductor-metal devices using silicon (Si) microwires. Monocrystalline Si in the shape of microwires are used which are developed through standard photolithography and etching. These microwires are assembled on secondary flexible substrates through a dry transfer printing by using a polydimethylsiloxane stamp. The conductive patterns on Si microwires are printed using a colloidal silver nanoparticles based solution and an organic conductor i.e. poly (3,4-ethylene dioxthiophene) doped with poly (styrene sulfonate). A custom developed spray coating technique is used for conductive patterns on Si microwires. A comparative study of the current–voltage (I–V) responses is carried out in flat and bent orientations as well as the response to the light illumination of the wires is explored. Current variations as high as 17.1 μA are recorded going from flat to bend conditions, while the highest I on/I off ratio i.e. 43.8 is achieved with light illuminations. The abrupt changes in the current response due to light-on/off conditions validates these devices for fast flexible photodetector switches. These devices are also evaluated based on transfer procedure i.e. flip-over and stamp-assisted transfer printing for manipulating Si microwires and their subsequent post-processing. These new developments were made to study the most feasible approach for transfer printing of Si microwires and to harvest their capabilities such as photodetection and several other applications in the shape of metal-semiconductor-metal structures

Graphene Gold Nanoparticle Hybrid Based Near Infrared Photodetector

This paper presents novel and simplistic approach towards the development of graphene based near infrared (NIR) photodetectors. The developed device comprises of Au nanoparticles integrated within the channel of the back-gated graphene field effect transistors. The introduction of Au nanoparticles enhanced response of the device under IR illumination due improved NIR absorption. Further, dynamic response of the device under IR illumination is presented. This study will trigger the development of novel hybrid graphene device for graphene based photodetectors in IR regime

Tuning Electrical Conductivity of CNT-PDMS Nanocomposites for Flexible Electronic Applications

This paper presents a study into the electrical conductivity of multi-wall carbon nanotube-polydimethylsiloxane (MWNT-PDMS) nanocomposite and their dependence on the filler concentration. It is observed that the electrical conductivity of the composites can be tailored by altering the filler concentration. Accordingly, the nanocomposites with filler weight ratio ranging from 1% to 8% were prepared and tested. Finally, the significance of results presented here for flexible pressure sensors and stretchable interconnects for electronic skin applications have been discussed

Ultra-thin chips for high-performance flexible electronics

Flexible electronics has significantly advanced over the last few years, as devices and circuits from nanoscale structures to printed thin films have started to appear. Simultaneously, the demand for high-performance electronics has also increased because flexible and compact integrated circuits are needed to obtain fully flexible electronic systems. It is challenging to obtain flexible and compact integrated circuits as the silicon based CMOS electronics, which is currently the industry standard for high-performance, is planar and the brittle nature of silicon makes bendability difficult. For this reason, the ultra-thin chips from silicon is gaining interest. This review provides an in-depth analysis of various approaches for obtaining ultra-thin chips from rigid silicon wafer. The comprehensive study presented here includes analysis of ultra-thin chips properties such as the electrical, thermal, optical and mechanical properties, stress modelling, and packaging techniques. The underpinning advances in areas such as sensing, computing, data storage, and energy have been discussed along with several emerging applications (e.g., wearable systems, m-Health, smart cities and Internet of Things etc.) they will enable. This paper is targeted to the readers working in the field of integrated circuits on thin and bendable silicon; but it can be of broad interest to everyone working in the field of flexible electronics

Piezoelectric graphene field effect transistor pressure sensors for tactile sensing

This paper presents graphene field-effect transistor (GFET) based pressure sensors for tactile sensing. The sensing device comprises GFET connected with a piezoelectric metal-insulator-metal (MIM) capacitor in an extended gate configuration. The application of pressure on MIM generates a piezo-potential which modulates the channel current of GFET. The fabricated pressure sensor was tested over a range of 23.54–94.18 kPa, and it exhibits a sensitivity of 4.55 × 10−3 kPa−1. Further, the low voltage (∼100 mV) operation of the presented pressure sensors makes them ideal for wearable electronic applications

Flexible FETs using ultrathin Si microwires embedded in solution processed dielectric and metal layers

This work presents a novel manufacturing route for obtaining high performance bendable field effect transistors (FET) by embedding silicon (Si) microwires (2.5 μm thick) in layers of solution-processed dielectric and metallic layers. The objective of this study is to explore heterogeneous integration of Si with polymers and to exploit the benefits of both microelectronics and printing technologies. Arrays of Si microwires are developed on silicon on insulator (SOI) wafers and transfer printed to polyimide (PI) substrate through a polydimethylsiloxane (PDMS) carrier stamp. Following the transfer printing of Si microwires, two different processing steps were developed to obtain top gate top contact and back gate top contact FETs. Electrical characterizations indicate devices having mobility as high as 117.5 cm2 V−1 s−1. The fabricated devices were also modeled using SILVACO Atlas. Simulation results show a trend in the electrical response similar to that of experimental results. In addition, a cyclic test was performed to demonstrate the reliability and mechanical robustness of the Si μ-wires on flexible substrates

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