Gregory L. Whiting

HIGHLY FLEXIBLE PRINTED ALKALINE BATTERIES BASED ON MESH EMBEDDED ELECTRODES

A flexible battery and a method to form the flexible battery include forming an anode by embedding an anode type electro-active material within a mesh material and associating an anode current collector with the anode. Similarly a cathode is formed by embedding a cathode type electro-active material within a mesh material and a cathode current collector is associated with the cathode. An electrolyte is located between the anode and cathode, and the arrangement is sealed.

Scalable printed electronics: an organic decoder addressing ferroelectric non-volatile memory

Scalable circuits of organic logic and memory are realized using all-additive printing processes. A 3-bit organic complementary decoder is fabricated and used to read and write non-volatile, rewritable ferroelectric memory. The decoder-memory array is patterned by inkjet and gravure printing on flexible plastics. Simulation models for the organic transistors are developed, enabling circuit designs tolerant of the variations in printed devices. We explain the key design rules in fabrication of complex printed circuits and elucidate the performance requirements of materials and devices for reliable organic digital logic.

A flexible high potential printed battery for powering printed electronics

Mechanically flexible arrays of alkaline electrochemical cells fabricated using stencil printing onto fibrous substrates are shown to provide the necessary performance characteristics for driving ink-jet printed circuits. Due to the dimensions and material set currently required for reliable low-temperature print processing of electronic devices, a battery potential greater than that sourced by single cells is typically needed. The developed battery is a series interconnected array of 10 low resistance Zn-MnO2 alkaline cells, giving an open circuit potential of 14 V. This flexible battery is used to power an ink-jet printed 5-stage complementary ring oscillator based on organic semiconductors.

Chemically modified ink-jet printed silver electrodes for organic field-effect transistors

Modification of ink-jet printed silver source and drain electrodes for organic field-effect transistors (FETs) with the electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) was investigated. Solution-based deposition of F4TCNQ onto ink-jet printed silver electrodes formed using either a nanoparticle-based or a metal organic decomposition ink, lead to a greater than tenfold improvement in FET mobility. Using these modified electrodes with the organic semiconductor 6,13-bis(triisopropylsilylethynyl) pentacene yields devices with a charge carrier mobility up to 0.9 cm2 V−1 s−1 and a current on/off ratio of 106.

From Printed Transistors to Printed Smart Systems

Printing as a manufacturing technique is a promising approach to fabricate low-cost, flexible, and large area electronics. Over the last two decades, a wide range of applications has been explored, among them displays, sensors, and printed radio-frequency identification devices. Some of these turned out to be challenging to commercialize due to the required infrastructure investment, accuracy or performance expectations compared to incumbent technologies. However, the progress in terms of material science, device, and process technology now makes it possible to target some realistic applications such as printed sensor labels. The journey leading to this exciting opportunity has been complex. This review describes the experience and current efforts in developing the technology at PARC, a Xerox Company. Printed smart labels open up low-cost solutions for tracking and sensing applications that require high volumes and/or would benefit from disposability. Examples include radiation tags, one-time use medical sensors, tracking the temperature of pharmaceuticals at the item level, and monitoring food sources for spoilage and contamination. Higher performance can be achieved with printed hybrid electronics, integrating microchip-based signal processing, wireless communication, sensing, multiplexing, as well as ancillary passive elements for low-profile microelectronic devices, opening up further applications. This technology offers custom circuitry for demanding applications and is complementary to mass printed transistor circuits. As an example, we describe a prototype sense-and-transmit system, focusing particularly on issues of integration, such as impedance matching between the sensor and circuits, robust printed interconnection of the chips, and compatible interface electronics between printed and discrete parts. Next-generation technologies will enable printing of entire smart systems using microchip inks. A new printing concept for the directed assembly of silicon microchips into functional circuits is described. The process is scalable and has the potential to enable additive, digital manufacturing of high-performance electronic systems.

Modelling of organic field-effect transistors for technology and circuit design

As organic field-effect transistors (OFETs) are preparing to take a key role in the flexible and low cost electronics applications, there is a pressing need for predictive device models to support technology optimization and circuit design. This paper focuses on the specific OFET features that challenge current modelling approaches. The presented modelling techniques range from the fundamental semiconductor equations to compact device model representations as required for implementation in advanced TCAD and EDA commercial tools. The models are verified with measured characteristics of advanced OFET device structures.

Open and closed loop manipulation of charged microchiplets in an electric field

We demonstrate the ability to orient, position, and transport microchips (“chiplets”) with electric fields. In an open-loop approach, modified four phase traveling wave potential patterns manipulate chiplets in a dielectric solution using dynamic template agitation techniques. Repeatable parallel assembly of chiplets is demonstrated to a positional accuracy of 6.5 μm using electrodes of 200 μm pitch. Chiplets with dipole surface charge patterns are used to show that orientation can be controlled by adding unique charge patterns on the chiplets. Chip path routing is also demonstrated. With a closed-loop control system approach using video feedback, dielectric, and electrophoretic forces are used to achieve positioning accuracy of better than 1 μm with 1 mm pitch driving electrodes. These chip assembly techniques have the potential to enable future printer systems where inputs are electronic chiplets and the output is a functional electronic system.

Flexible printed sensor tape based on solution processed materials

In this report, the fabrication of inkjet-printed complementary organic inverters was demonstrated. The acceleration sensors were integrated with printed inverters to enable amplification of sensor signals. This demonstration of sensors with amplifiers showed a potential printing method to fabricate low-cost, mechanically flexible sensor system from polymers.

Flexible Hybrid Electronic Circuits and Systems

Printed organic electronics are being explored for a wide range of possible applications, with much of the current focus on smart labels, wearables, health monitoring, sensors and displays. These applications typically integrate various types of sensors and often include silicon integrated circuits (IC) for computation and wireless communications. Organic thin film transistors (TFT), particularly when printed, have performance and yield limitations that must be accommodated by the circuit design. The circuit design also needs to select sensor technology, ICs and other circuit elements to integrate with the TFTs and match the functional and performance requirements of the application. This paper describes organic TFT properties and strategies for circuit and sensor design, with examples from various sensor systems.

Micro chiplet printer for micro-scale photovoltaic system assembly

The micro-CPV concept uses an array of micro unit cells (or elements) such that the material usage, weight, and the required structural strength can all be scaled down favorably. Unfortunately, one of the essential unfavorable scaling factors is the assembly cost due to the many micro scale components that must be deposited, positioned, oriented, and connected over large areas. By using a dynamic electric field template, we successfully demonstrate chiplet printing - assembling a desired solar cell chip at a designated location with well controlled orientation. Xerographic printing systems utilizing this method can be extended to provide high-throughput, on-demand heterogeneous assembly of micro-CPV systems.