Apple's U.S. Patent No. 8,638,549 for an "Electronic device display module" describes a two-sided glass laptop display housing which carries the usual screen on its front face. On the rear, however, the module holds photovoltaic cells for solar charging, a secondary display and sensors for touch input.
As noted in the patent, the two-sided display may be manufactured using a variety of materials, including metal, ceramic, fiber composites and glass. In some embodiments, the rear of the display can be composed of electrochromic glass that allows light to pass through only when desired.
Much like the current MacBook lineup, a logo is disposed on the rear of the housing and can be illuminated via the same LED lighting as the front-facing display. Unlike current models, which feature an Apple logo made from translucent plastic embedded in the display chassis, the patent calls for the logo to be screened out of a patterned ink layer.
As noted above, in one embodiment the rear panel is made of electrochromic glass. Sometimes referred to as electrically switchable glass, the material can change state from translucent to transparent when a voltage is applied across its surface. This allows for a rear-facing display to remain hidden until user activation.
The electrochromic layer may also be disposed in a more granular fashion. In some cases, the layer that is divided into multiple sections like halves, quarters, eighths or other quadrants. Each section can be activated independently, allowing individual control and localized adjustments for light passage. For example, the layer may be activated to display a logo or reveal a small LCD display.
As for the touch sensors, the document implies any number of technologies can be deployed, including capacitive, optical and acoustic, among others. The sensors are able to collect touch data which is then translated into system commands. For example, a user can touch a certain area on the rear panel to unlock a magnetic latch mechanism that holds the display housing closed. In another example, pass codes, media controls and other software input may be managed from the rear sensor array.
Finally, Apple proposes a photovoltaic system may also be disposed between the rear panel and front-facing LCD screen. With the glass backing and electrochromic layer in transparent mode, light is able to hit photovoltaic cells, which in turn converts the energy into electrical power for storage or immediate use.
The patent goes on to describe in detail LED lighting techniques, construction and a variety of build options relating specifically to the display housing.
It is unknown if Apple will one day implement such an advanced component in its MacBook series of products, though the company has successfully manufactured dual-glass designs in smaller devices like the iPhone 4 and 4S.
Apple's two-sided laptop display patent was first filed for in 2010 and credits Adam T. Garelli, Dinesh C. Mathew, Thomas W. Wilson, Jr., Keith J. Hendren, Peteris K. Augenbergs, Brett W. Degner, Bradley J. Hamel, Michael A. Damlanakis and Patrick Kessler as its inventors.