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The Future of Ink

Michael H. Suo's picture

Since I know (or was told 20 minutes ago) that some of you are interested in large area electronics and displays, I thought I would throw something out for you.

Lately, e-book readers have been a new trend in the tech industry. The potential for it is incredible: hundreds of books in the palm of your hand, digitized content distribution, and infinite number of bookmarks, searchable text, hyperlinks between books; the list goes on. However, all these benefits come at a price; namely battery life and readability.

But what kind of display should they use? The average LCD screen has about 72 dpi (dots per inch), meaning that there are 72 pixels in every inch of screen. While that's passable for regular computer usage, anyone who's tried heavy reading will tell you that it's just not clear enough. By comparison, the average newspaper has over 300 dpi, and the average book has about 400 dpi.

What can be done about this? Obviously, traditional screens won't work, as the cost of producing display with high dpi increases exponentially. But our good friends at E-Ink Corporation have since developed an entirely new kind of display especially for the purpose of reading e-books. Named (appropriately) e-ink, the company's site explains the technology like this: "millions of tiny microcapsules, about the diameter of a human hair . . . each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a negative electric field is applied, the white particles move to the top of the microcapsule where they become visible to the user. This makes the surface appear white at that spot. At the same time, an opposite electric field pulls the black particles to the bottom of the microcapsules where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot." The dpi on the typical e-ink display is 150-200, which is plenty for comfortable reading.

The advantage of this approach isn't just in the dpi, but also battery life: electricity is only used when turning the page. One prototype based on e-ink technology has been displaying the same page for 3 years, and doesn't show any signs of stopping yet.

However, there are problems too. Obviously, the major one is that since each microcapsule is filled with only two kinds of particle, only black and white displays can be made. Another issue concerns usability; the screen must refresh itself each time the page is turned, forcing the reader to wait a second or two and showing an annoying black flash before displaying the next page.

Despite these complications, already many companies are jumping on the e-ink bandwagon. Sony, iRex (a spin-off of Philips Electronics), Amazon, and Staretek are all planning e-book readers, although only Sony and iRex actually have models out in the wild. Fujitsu and Hitachi are working on readers with e-ink that allows color, while HP, Epson, Siemens, Philips, Toppan, Bridgestone Tires, and some Scottish guys are working on flexible e-ink displays. Finally, others like Panasonic are still fiddling with LCD screens, but to the same e-book-centric ends.

But display technology isn't all that matters to the success of the e-book. How will users receive books? How much will they pay? What format will the books be in? All these are questions that each company has different answers to. Both Sony and iRex have proprietary distribution software (Sony Connect and iRex IDS, respectively), and although it hasn't been confirmed, it's pretty much a given that others will have their on services.

Sony has gone one step farther, offering books in a proprietary format, which can't be viewed by most other e-book readers. On top of that, they have included DRM (Digital Rights Management) that only allows the file to be viewed on 6 different devices. Many have argued that Sony is digging a hole for itself; they failed in the music store race because their format was useless on most MP3 players. However, others have noted that the piracy of e-books (already a flourishing venture) will be a significant threat to all purveyours of e-books and readers.

Reaction to the two consumer models--the Sony Reader and the iRex iLiad--have been mixed, with some touting the portability and clarity of the display, and others boo-booing the long pageturn times and non-intuitive interfaces. Some have observed that the iLiad seems to have been rushed out the door in attempt to be first on the market, and should still be in testing stages. Initial response of the Sony Reader has been postive, albeit with some misgivings.

A lot of question are still unanswered, and many details remain unrevealed. The e-reader industry is still in its infant stages, but be sure to watch it carefully for more developments in the future.

Useful links:


Zhigang Suo's picture

Springer early this year announced that they would offer a huge collection of books in the ebook format.

Stanford University is talking about a book-free library, possibly by 2020--a short 15 years from now.

Most researchers have already been downloading journal articles, but are still printing artcles on paper. I wonder if technologies like e-ink will change the habit in next 10 years.

Once the technology is proven, we may still have some sociological debates. Will books be with us forever, or are they merely a histoical accident? If all knowledge is interconnected, why should we bother with books at all, electronic or print?

For the time being books have the convenient size for distribution of knowledge. But really, a book is too long for human concentration and too short for a subject of any substance. Once e-readers become popular, perhaps the book as a format of publishing will meet its end. Books may as well become historic artifacts, and be used for occasions of romance and nostalgia, as candels are today.

Perhaps we should leave such speculations to more competent people, and focus on using mechanics to advance the technology.

For some time Teng Li has been writing a wonderful blog on large area electronics. The blog aims to link applications to technology and to mechanics.

Michael H. Suo's picture

I think e-books are merely an extension of print books. Therefore, it's conceivable that they will replace regular books entirely. But I don't think print books will become obselete, but rather become luxury items, rather like jewelry. The Diamond Age, a novel by Neal Stephenson, speculates along this line of reasoning.

However, the written word is definitely not the ultimate form of knowledge distribution or even of communication. It's just the best we've come up with so far.

Imagine. If some omnipotent being wanted tell someone to build, say, an ark, would this god write down a note and send it to him? Of course not. The god would probably send it to the mortal in the form of a dream, along with all the necessary sensations and thoughts to ensure perfect understanding. Indeed, a dream (or something which simulates thoughts and senses) would be the ideal form of communication.

Knowledge distribution, also, would probably benefit from having exact simulation of thought, so mastery of a topic would be a simple process of downloading knowledge into your brain.

Nanshu Lu's picture

Thanks Michael  for introducing me into this emerging technology of E-Book. 

It just occured to me that another reason I prefer  books or printed articles is I can write down flash ideas or draw intuitive figures immediately beside the text I'm reading. Each time I review or discuss with others the handwriten footnotes are very important reminder to me. Since it's not as simple as a bookmark I am wondering whether the E-book has this kind of feature, say the easiness of writing and erasing? To completely replace the papar this issue may also be taken into account.

Michael H. Suo's picture

Handwritten notes, or "annotations" as they're called, are possible in the iRex iLiad. Using a stylus, you can write on the touchscreen as you would a normal piece of paper. The annotations are then saved onto the flash memory, to be recalled whenever that particular page is viewed. Most reviewers have called the touchscreen "similar to that of a Palm Pilot's" in terms of responsiveness and accuracy.

Teng Li's picture

Michael, I'm amazed by the depth of your study on e-books. Thanks for pointing out links to various players in this emerging technology.

While the major challenges for flat panel video displays (e.g., LCD TV, OLED TV) are size and cost, a particular challenge for e-book is resolution. As Michael pointed out, printed newspaper and books have resolutions of about 300~400dpi, a rule of thumb for resolution of comfortable reading. The resolution of e-ink is largely determined by the size of the microcapsules. Currently, various prototypes of electronic paper using e-ink have demonstrated resolution of 300dpi (see here for some examples). The readability of e-books will be improved to be acceptable sooner or later. Plus the human eyes can hardly tell difference if the resolution of the text is above 400 dpi. Therefore the resolution won't be a longterm challenge for e-book.

The current price of Sony e-book is arround $400, about twice of iPod nano. The widespread use of e-book (or further replacement of traditional paper-based books and newspaper) essentially depends low cost. One promising way to effectively decrease the cost of e-book is to fabricate through roll-to-roll printing (see here for an illustration). While roll-to-roll printing has been used to fabricate thin-film solar cells at low cost (e.g.,see here and here ), its application to display fabrication is still at infancy. Various technical hurdles exist, such as impurity due to contact, damage due to handling, and yield management, not to mention financial challenges for both fundamental research and volume production facility.

Technical and finacial challenges aside, flexible displays projects huge market potential, about $2 billion by 2015 and will experience substancial growth in the next five years (for example, see here for a recent study on flexible display revenue by applications).

Zhigang Suo's picture


Thank you very much for the wealth of information on this fascinating technology. Micheal has been urging me to look into ebooks ever since he knew that you and I are doing research on micromechanics of macroelectronics. Have you seen any specific mention of materials and mechanics issues in the ebook technology? In what sense ebooks are flexible displays?

Incidentally, you forgot to make a hyperlink in your last sentence.

Teng Li's picture

While the advent of e-ink enables novel display designs such as e-books, mechanics and materials challenges in designing such devices still form technology barriers for the future success of of e-books and other flexible display products. For example, these organic-based electronics are very vulnerable to moisture, thus an encapsulation layer is needed. Such a layer often consists of alternating sublayers of organic and inorganic materials to provide both ruggedness and airtightness. The mechanics understanding and materials choice of the encapsulation layer is far from mature. Scratch resistance of the display surface is another issue. Currently the materials used to protect the surface of your LCD display are inorganic, and are not necessarily suitable for the design of flexible displays. A particular drawback of the current e-ink technology is the slow refresh rate (it takes about 1 second to turn a page), which could possibly be related to the size of the microcapsules and the diffusion of the black/white subcapsules in the fluid.

I was on a NIST workshop on nanomanufacturing this week. As pointed by people in industry, one critical challenge for the display products is the defect detection. While defects in the functional layers of displays essentially dominate the device failure, an effective metrology on such defects is just unavailable. As for roll-to-roll printing, the layer-to-layer registration and alignment are particularly critical and more challenging for manufacturing large area displays, compared to manufacturing thin-film solar cells.

In two earlier posts (here and here), I listed some review papers on flexible electronics, including one paper particularly addressing materials challenges.

Current available products of e-books are not flexible yet. But more and more prototypes of flexible displays are coming, see here and here for two examples.

Thanks Michael for such an excellent overview of E-books. It can be expected that the needs of mobile display will increase exponentially due to the latest advances in wireless bandwidth and processor technologies. Particular important to mobile reading is portability, higher information content, comfortable reading in dynamic environments and low power consumption. The present display technology such as LCD still cannot match the reading experience with printed papers. As Michael mentioned, LCD currently has issues such as power consumption and limitation of viewing angles. In fact, the display and backlight of the LCD consumes a significant part the battery power in the current notebook and PDA devices.

The microencapsulated electronic display, i.e. the i-ink approach, uses millions of tiny micro capsules, each containing charged submicron pigments that move under an externally applied field to form an image. For instance, each microcapsule contains positively charged white particle and negatively charged black particles suspended in a clear fluid. These capsules serve as liquid and particle containers, sandwiched between a transparent electrode (the displace surface) and an electrode grids (the back) so that the pixel can be addressed individually. The resolution is eventually determined by the electrode grids not the capsule size. Subcapsule addressing can be achieved. Changing the voltage polarity can cause white or black nanoparticles to move to the display surface to lighten or darken a pixel. Each microcapsule can be controlled by several electrode lines to induce a mixture of white and black nanoparticles on the displace surface in a finer scale, which gives gray scale. The flow of nanoparticles in the fluid is essential to the technique and of interest from a mechanics point of view. The response time will depend on the mobility of the particles M (or viscosity of the fluid). The motion of small particles in a liquid is in the realm of very low Reynolds numbers so that the drag force overwhelms. So the particle reaches its steady velocity almost instantly. Consider two parallel electrodes separated by d, the driving force is proportional to V/d (field strength), the velocity is ~MV/d. The response time is the time to transit particles from back to the front, taking time ~ d^2/(MV). Thus the response time can be reduced by using lower viscosity, closer electrodes or higher voltage. Another interesting aspect is the image display time after the electric field is removed. The materials need to be designed so that it is "sticky" to the surface against any vibration or Brownian motion. One the other hand, the adhesion should be small enough so that the electric field can easily move them from the display surface to the back. Flexibility of the display is coupled to the flexibility of the electrodes, where mechanics and materials issue also come in.

Making colorful display is still a challenge for the microencapsulated electronic display. I learned from some news that first generation has been made by utilizing a color-filter array. I guess eventually some intrinsic color particle arrangement will be the solution, which would require higher degree of control and design.

Ying Li's picture

I have read a artical about e-newspaper last year from the Scientific American. It told us that two companys in the world had produced the cheap and useful  e-newspaper. The e-newspaper could be curled as the newspaper we read daily!  The follow link is a design from IBM.

May be we will use it in several years. But I think there are also many questions.Firstly, the pollution is very serious . Can we control it in the industries? Secondly, our eyes is also a problems.There are many four-eyed fishes in the world and most of them is caused by the sitting front the computers. The e-ink may also cause the same questions. That is the real questions I want to think about. Maybe some people can answer me. Thank you!  

Zhigang Suo's picture

The paper industry emits the fourth-highest level of carbon dioxide among manufacturers, cited in today's New York Times. One more reason to move to e-readers.

Micheal has just got his new Sony e-reader. It is an absolute engineering wonder! It reads better than cheap paperback books. The words look sharp, and have the feel of words printed on paper. It does not look like the e-reader will strain eyes more than a regular book does.

The screen is somewhat smaller than a page of a paperback. The size seems to be ideal for reading fictions, but is too small, I think, for technical books, where we'd like to see words, equations, and figures all on the same page.

Michael has promised to write an account of his experience with the e-reader.

Robin Selinger's picture

My colleagues at Kent State University's Liquid Crystal Institute are working on FLEXIBLE liquid crystal display technology.  A flexible display ebook will have a look and feel that's more like a regular book and less like a rigid Gameboy or PDA.

Here is info about Kent State's patent for flexible LC displays: 

What's more, Kent State scientists have also invented a "no-power" bistable display technology which uses battery power only when the image is changed. These are available now from Kent Displays, Inc. for signage and as a display on a USB flash drive. See details at

 And yes, it's possible to combine flexibility with bistability. See this paper from Prof. John West's group: 

(The first author, Ebru Buyuktanir, is finishing her PhD soon and will be going on the job market sometime in the coming year. If you'd like to recruit her to join your organization, you can find her email in the directory at .)

I've been at the LCI since summer '05 and am thrilled to have joined such an innovative and exciting organization!

 -Robin Selinger, Professor, Chemical Physics Interdisciplinary Program, Liquid Crystal Institute, Kent State University


Zhigang Suo's picture

The New York Times reports on the continuing decline of major newspapers. I have been reading New York Times free online. Michael has even installed a software on my computer to block all the ads. I feel guilty for not supporting this great newspaper, but who am I to support every worthy cause? It seems that basic changes must be made for newspapers to survive.

We mechanicians know all about challenges of our time. A while ago I posted an entry entitled Let Us Seize the Greatest Opportunities of Our Time, where I talked about iMech. The entry led to the name of this site: iMechanica.

Zhigang Suo's picture

In my mind, the ebook symbolizes two aspects for us mechanicians. The technology has a mechanical principle in its core. The content is becoming digital. Both aspects will be with us for a long time. Previous comments have focused on the first aspect, now I'd like to comment on the second aspect.

Michael has thoroughly enjoyed his e-reader, but has been telling me that the barrier for people to adopt this wonderful technology is copyright: People have very limited choice for content. Sony bookstore only offers about 10,000 titles.

Perhaps we should be patient. Things are changing, however slowly. In an earlier comment I noted that Springer had announced that they would offer a huge collection of books in the ebook format. Legal experts are also talking about reforming copyright law.

In the long history of human pursuit of knowledge, copyright must be a historical accident. It is contingent upon a sequence of events, mostly technological, such as the invention of press, paper, and book. Now the technology of knowledge distribution and storage has changed, so should the law.

I grow up in a country where there has been disregard for copyright, a fact that has long been widely criticized. Is my old country simply ahead of time, however ironic, or should it enforce stringent copyright law, which seems to be of dubious merit for future?

I hope someone with more knowledge to illuminate us on these issues.

Update on 19 November 2006. Publishing industries share many similarities with the music industries. Here is today's post by Micheal Arrington, of Techcrunch, entitled Replacing DRM with a Music Tax Is Incredibly Stupid.

Update on 20 November 2006.  Posts in Techdirt by Mike on the textbook industry and newspaper industry

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