Editing Electronic paper (section)

====Microencapsulated electrophoretic display====
[[File:How It Works, Black & White Capsules.pdf|thumb|275px|right|Scheme of an electrophoretic display]]
[[File:Epd color.svg|thumb|275px|right|Scheme of an electrophoretic display using color filters]]
[[File:Kindle 3 texture (crop).jpg|thumb|Macro photograph of Kindle 3 screen; microcapsules are evident at [//upload.wikimedia.org/wikipedia/commons/5/54/Kindle_3_texture_%28crop%29.jpg full size.]]]

In the 1990s another type of electronic ink based on a microencapsulated electrophoretic display was conceived and prototyped by a team of undergraduates at MIT<ref>{{cite news|title= A New Printing Technology Sets Off a High-Stakes Race|url= https://www.wsj.com/articles/SB946939872703897050|newspaper= Wall Street Journal|access-date= 2015-11-27|issn= 0099-9660|first= Alec Klein Staff Reporter of The Wall Street|last= Journal|archive-date= 2015-12-08|archive-url= https://web.archive.org/web/20151208050730/http://www.wsj.com/articles/SB946939872703897050|url-status= live}}</ref> as described in their Nature paper.<ref name="e_ink_nature"/> J.D. Albert, [[Barrett Comiskey]], Joseph Jacobson, Jeremy Rubin and Russ Wilcox co-founded [[E Ink Corporation]] in 1997 to commercialize the technology. E Ink subsequently formed a partnership with [[Philips|Philips Components]] two years later to develop and market the technology. In 2005, Philips sold the electronic paper business as well as its related patents to [[Prime View International]]. <blockquote>"It has for many years been an ambition of researchers in display media to create a flexible low-cost system that is the electronic analog of paper. In this context, microparticle-based displays have long intrigued researchers. Switchable contrast in such displays is achieved by the electromigration of highly scattering or absorbing microparticles (in the size range 0.1–5 μm), quite distinct from the molecular-scale properties that govern the behavior of the more familiar liquid-crystal displays. Micro-particle-based displays possess intrinsic bistability, exhibit extremely low power d.c. field addressing and have demonstrated high contrast and reflectivity. These features, combined with a near-[[Lambertian reflectance|lambertian]] viewing characteristic, result in an 'ink on paper' look. But such displays have to date suffered from short lifetimes and difficulty in manufacture. Here we report the synthesis of an electrophoretic ink based on the microencapsulation of an electrophoretic dispersion. The use of a microencapsulated electrophoretic medium solves the lifetime issues and permits the fabrication of a bistable electronic display solely by means of printing. This system may satisfy the practical requirements of electronic paper."<ref>{{cite journal|title= An electrophoretic ink for all-printed reflective electronic displays|journal= Nature|date= 1998-07-16|issn= 0028-0836|pages= 253–255|volume= 394|issue= 6690|doi= 10.1038/28349|first1= Barrett|last1= Comiskey|first2= J. D.|last2= Albert|first3= Hidekazu|last3= Yoshizawa|first4= Joseph|last4= Jacobson|bibcode= 1998Natur.394..253C|s2cid= 204998708}}</ref></blockquote>

This used tiny microcapsules filled with electrically charged white [[molecule|particles]] suspended in a colored [[mineral oil|oil]].<ref name="e_ink_nature">{{cite journal |last1= Comiskey |first1= B. |last2= Albert |first2= J. D. |last3= Yoshizawa |first3= H. |last4= Jacobson |first4= J. |year= 1998 |title= An electrophoretic ink for all-printed reflective electronic displays |doi= 10.1038/28349 |journal= Nature |volume= 394 |issue= 6690 |pages= 253–255|bibcode= 1998Natur.394..253C |s2cid= 204998708 }}</ref> In early versions, the underlying [[circuitry]] controlled whether the white particles were at the top of the capsule (so it looked white to the viewer) or at the bottom of the capsule (so the viewer saw the color of the oil). This was essentially a reintroduction of the well-known [[electrophoresis|electrophoretic]] display technology, but microcapsules meant the display could be made on flexible plastic sheets instead of glass.
One early version of the electronic paper consists of a sheet of very small transparent capsules, each about 40 [[micrometre|micrometer]]s across. Each capsule contains an oily solution containing black dye (the electronic ink), with numerous white [[titanium dioxide]] particles suspended within. The particles are slightly negatively [[electric charge|charged]], and each one is naturally white.<ref name="newscientist_1"/>
The screen holds microcapsules in a layer of [[liquid]] [[polymer]], sandwiched between two arrays of electrodes, the upper of which is transparent. The two arrays are aligned to divide the sheet into pixels, and each pixel corresponds to a pair of electrodes situated on either side of the sheet. The sheet is laminated with transparent plastic for protection, resulting in an overall thickness of 80 micrometers, or twice that of ordinary paper.
The network of electrodes connects to display circuitry, which turns the electronic ink 'on' and 'off' at specific pixels by applying a voltage to specific electrode pairs. A negative charge to the surface electrode repels the particles to the bottom of local capsules, forcing the black dye to the surface and turning the pixel black. Reversing the voltage has the opposite effect. It forces the particles to the surface, turning the pixel white. A more recent implementation of this concept requires only one layer of electrodes beneath the microcapsules.<ref>{{cite news |last=Sample |first=Ian |newspaper=New Scientist |title=Roll The Presses |date=24 April 2001 |url=https://www.newscientist.com/article/dn659-roll-the-presses.html |access-date=20 November 2011 |archive-date=9 March 2011 |archive-url=https://web.archive.org/web/20110309061210/http://www.newscientist.com/article/dn659-roll-the-presses.html |url-status=live }}</ref><ref>{{cite journal |first1=John A |last1=Rogers |first2=Zhenan |last2=Bao |first3=Kirk |last3=Baldwin |first4=Ananth |last4=Dodabalapur |first5=Brian |last5=Crone |first6=V R |last6=Raju |first7=Valerie |last7=Kuck |first8=Howard |last8=Katz |first9=Karl |last9=Amundson |first10=Jay |last10=Ewing |first11=Paul |last11=Drzaic |title=Paper-like electronic displays: Large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks |date=24 April 2001 |journal=PNAS |volume=98 |issue=9 |pages=4835–4840 |doi=10.1073/pnas.091588098 |pmid=11320233 |pmc=33123|doi-access=free }}</ref> These are commercially referred to as Active Matrix Electrophoretic Displays (AMEPD).