Paintable Electronics? NIST Studies Spray-On Manufacturing of Transistors

From the 3/30/10 issue of NIST Tech Beat:

A multidisciplinary research team at the National Institute of Standards and Technology (NIST) has found* that an organic semiconductor may be a viable candidate for creating large-area electronics, such as solar cells and displays that can be sprayed onto a surface as easily as paint.

While the electronics will not be ready for market anytime soon, the research team says the material they studied could overcome one of the main cost hurdles blocking the large-scale manufacture of organic thin-film transistors, the development of which also could lead to a host of devices inexpensive enough to be disposable.

This airbrush technique deposits a well-studied material called P3HT to create spray-on transistors, which perform comparably to lab-standard equivalents made by spin coating.

Silicon is the iconic material of the electronics industry, the basic material for most microprocessors and memory chips. Silicon has proved highly successful as a substance because billions of computer elements can be crammed into a tiny area, and the manufacturing process behind these high-performance chips is well-established.

But the electronics industry for a long time has been pursuing novel organic materials to create semiconductor products—materials that perhaps could not be packed as densely as state-of-the-art silicon chips, but that would require less power, cost less and do things silicon devices cannot: bend and fold, for example. Proponents predict that organic semiconductors, once perfected, might permit the construction of low-cost solar cells and video displays that could be sprayed onto a surface just as paint is.

“At this stage, there is no established best material or manufacturing process for creating low-cost, large-area electronics,” says Calvin Chan, an electrical engineer at NIST. “What our team has done is to translate a classic material deposition method, spray painting, to a way of manufacturing cheap electronic devices.”

The team’s work showed that a commonly used organic transistor material, poly(3-hexylthiophene), or P3HT, works well as a spray-on transistor material because, like beauty, transistors aren’t very deep. When sprayed onto a flat surface, inhomogeneities give the P3HT film a rough and uneven top surface that causes problems in other applications. But because the transistor effects occur along its lower surface—where it contacts the substrate—it functions quite well.

Chan says the simplicity of spray-on electronics gives it a potential cost advantage over other manufacturing processes for organic electronics. Other candidate processes, he says, require costly equipment to function or are simply not suitable for use in high-volume manufacturing.

* C.K. Chan, L.J. Richter, B.Dinardo, C.Jaye, B.R. Conrad, H.W. Ro, D. S. Germack, D.A. Fischer, D.M. DeLongchamp, D. J. Gundlach. High performance airbrushed organic thin film transistors. Applied Physics Letters, 96, 133304. March 30, 2010. doi:10.1063/1.3360230

Simple Antenna Demos Antenna Polarization

I’m always amazed when things actually work. So you can imagine my amazement when I actually got the demo shown in the Make: Magazine video below to work.

Diana, KC2UHB, used her lightbulb/antenna combo to demonstrate the principle of directional antennas by using a Yagi as her transmitting antenna. I didn’t have a Yagi handy, so I used one of my home-made J-pole antennas.

Because the J-pole isn’t directional, I obviously couldn’t use it to demonstrate directionality, but it worked quite nicely to demonstrate the principle of polarization. All I had to do was to position the receiving antenna so that it was parallel to the J-pole and the light was nice and bright. Then, I rotated the antenna until it was perpendicular to the J-pole. The light got dimmer and dimmer until eventually you couldn’t see it emitting any light at all. Rotate it back to perpendicular and the bulb burned brightly again.

I think I’ll try to make a video of this down at the Museum this Saturday.

The Transistor Museum Dedicated to Preserving the History of Semiconductors

The Transistor Museum’s tagline is “Dedicated to Preserving the History of the Greatest Invention of the 20th Century,” and it does a pretty good job of it. On this website you’ll find articles on:

  • The First Germanium Hobbyist Transistors
  • Early Transistors at Motorola
  • The First Transistor in Space
  • Norman Krim, the Father of the CK722 Transistor
  • a whole lot more

Like all good museums, they also have a museum store. They sell a couple of books on the early semiconductors as well as some of those transistors themselves. They’re kind of pricey, though. A 2N60 or 2N609, for example, costs $20.

Ferrite Beads are an Elegant Solution

Here’s a cute article on the use of ferrite beads written by a couple of engineers at Intersil. Some interesting stuff about why ferrite inductors work so well.

What the Heck is Phase Noise, Anyway?

Hams sometimes bandy about the term “phase noise,” but few hams really understand it. Most of us can figure out that less phase noise is better than more phase noise, but that’s about as far as our knowledge goes.

To help you understand the concepts, there is a paper about phase noise on While there is a lot of complicated, engineering math in the paper (this is complicated stuff, after all), the first two pages offer a simple explanation of the basic concepts. In explaining how phase noise affects a system, the paper notes:

In transmitters local oscillator noise is amplified by the subsequent amplifier stages and is eventually fed to the antenna together with the wanted signal. The wanted signal is therefore surrounded by a band of noise originating from the phase noise of the local oscillator. Therefore the noise generated can spread over several kHz masking nearby lower power stations as shown in figure 3 (shown below).

To relate this to a common example in ham radio, this is why you want rigs with low phase noise at your Field Day operation. Rigs that have poor phase noise performance will seriously raise the noise floor, affecting all of the other radios, especially those attempting to operate on the same band. For example, a 40m phone station running a rig with relatively high phase noise might swamp a station running 40m CW.

Make: Tackles Learning Electronics

The publishers of Make: magazine have just come out with a book on the basics of electronics. You can download a sample of the book that include the table of contents, the index, and Chapter 1.

From what I could see I like it. Right off the bat, they have you build a little LED circuit consisting of a battery, potentiometer, and LED. With just those three components, they’re able to demonstrate the concepts of voltage, resistance and current, as well as teach you how to use a multimeter.

Read more

New Spectrum Allocation Chart

No ham shack should be without a spectrum allocation chart. Now, Tektronix, the oscilloscope maker, is now offering a new one. Here’s what their website has to say:

New Worldwide Spectrum Allocations Poster Request Form

Thanks your interest in our NEW poster. It provides a color-coded view of the worldwide spectrum allocations for all ITU (International Telecommunications Union) regions. It’s the only graphical poster that shows the international spectrum allocations in an easy-to-find format.

There’s a form to fill out, so that they can get your address, and the poster will be winging its way to you.

EE Times Taps Ten Technologies to Watch

The editors at EE Times have compiled a list of 10 emerging technologies to watch in 2010:

  1. Biofeedback or thought-control of electronics could give people with disabilities, the military, and consumers new ways to control user interfaces.
  2. The possibility of rapidly printing multiple conductive, insulating, and semiconductive layers to create electronics could significantly lower the cost of manufacturing electronics.
  3. The development of plastic memory could lead to rewritable, non-volatile memory capable of retaining data for more than 10 years and one million cycles.
  4. Maskless lithography could be a spoiler in the effort to replace immersion lithography with extreme ultraviolet lithography.
  5. Parallel processing will become better understood and more widely used as initiatives such as OpenCL and Cuda expand the understanding of how multiple processors will be programmed and used for increased computational and power efficiency.
  6. Energy harvesting will increasingly be used in devices, such as vibration-powered wireless sensors on machinery or vehicles, or motion-powered mobile phones.
  7. Biology and technology will continue to merge, building off of devices such as under-the-skin tags for pets and heart pacemakers for humans.
  8. Resistive RAM, or the memristor, will continue to evolve.
  9. The depth of the interconnect stack on top of the leading-edge silicon surface could lead to a splitting of front-end fab production into surface and local interconnect.
  10. Battery technologies will emerge to power an increasingly diverse number of devices.

Why Capacitor Polarity is Important

Dave Jones’ latest EEVBlog episode is a graphical demonstration of why it’s important to get the polarity of electrolytics and tantalum capacitors right:

EEVBlog also has some interesting episodes on test equipment, microcontrollers, and product design. Check it out.

Learn Digital Logic on the Web

One topic that a lot of people have some trouble with when taking the Extra Class exam is digital logic. I think one of the reasons for this is that while it is electronics, the logic element is different from the other types of technology we deal with in ham radio.

To help students learn the concepts of digital logic, the Department of Informatics at the University of Hamburg has developed the Hamburg Design System, or HADES for short. HADES is an object-oriented, all-Java, Beans- and Web-based, visual design and simulation environment.

With this system, you can play with digital logic without actually building any circuits or connecting up any test equipment. There are canned demonstrations, such as this digital clock, or you can build your own circuits with HADES’ graphical editor, library of component models, and the discrete-event-based simulation engines.