[caption id="attachment_16875" align="aligncenter" width="618"] Todd Hamilton's concept of Apple's iWatch.[/caption] Forget processor speed, or camera megapixels, or even screen size: for Silicon Valley’s tech giants, the burning question is how to build mobile devices capable of carrying a battery charge for as long as possible. Apple spent years experimenting with ways to charge iPhones and iPods with solar power, according to a new article in The New York Times. While the company eventually abandoned that investigation, it’s reportedly toying with alternative ways to power up its much-rumored “iWatch” smart-watch, an unnamed source “briefed on the product” told the newspaper. (According to rumors, the “iWatch” will feature a curved-glass screen and the ability to run some variation of iOS apps, in addition to telling time.) A charging method that doesn’t involve plugging an “iWatch” into the nearest electrical socket would allow Apple to solve one of the biggest conundrums facing smart-watches, namely that the small battery would necessitate removing and charging the timepiece once a night (if not several times a day, for heavy users), which isn’t exactly something that people want to do with a watch. The company has reportedly considered charging the device through arm movement or even solar power (the latter via a photosensitive layer embedded in the device); but making such concepts a reality could take several years, even with Apple’s recent hiring spree of power-technology engineers and scientists. Solar power in particular would require some major innovations to overcome the technology’s current inefficiencies, not to mention peoples' tendency to spend most of their time inside and out of the sun. Considering how Apple wants to release the "iWatch" this year (again, if rumors prove correct), there's a good chance it won't rely on solar. Samsung, Google, and other companies that manufacture mobile devices have worked for a long time on batteries that are smaller, more efficient, and charged via new methods. Several years ago, Palm Pre owners could power their smartphone by placing it atop a Touchstone charging dock; Nokia and Samsung later mimicked that technology for their own mobile hardware. But as smartphones have gotten smaller and thinner, and wearable electronics such as smart-watches and augmented-reality headsets begin to occupy the public attention, the pressure to create more efficient power sources has only increased.   Image: Todd Hamilton