While mobile phones have found broad application in bringing health, financial, and other services to the developing world, usability remains a major hurdle for novice and low-literacy populations. In this article, we take two steps to evaluate and improve the usability of mobile interfaces for such users. First, we offer an ethnographic study of the usability barriers facing 90 low-literacy subjects in India, Kenya, the Philippines, and South Africa. Then, via two studies involving over 70 subjects in India, we quantitatively compare the usability of different points in the mobile design space. In addition to text interfaces such as electronic forms, SMS, and USSD, we consider three text-free interfaces: a spoken dialog system, a graphical interface, and a live operator. Our results confirm that textual interfaces are unusable by first-time low-literacy users, and error prone for literate but novice users. In the context of healthcare, we find that a live operator is up to ten times more accurate than text-based interfaces, and can also be cost effective in countries such as India. In the context of mobile banking, we find that task completion is highest with a graphical interface, but those who understand the spoken dialog system can use it more quickly due to their comfort and familiarity with speech. We synthesize our findings into a set of design recommendations.

The electrical design of a lithium-ion battery, including current collector dimensions and tabbing layout, can have a significant impact on its performance and aging behavior. This work describes a coupled electrochemical + electrical network model to quantify the impact of current collector resistance on performance, current distribution, and internal state heterogeneity in cells with cylindrically wound jellyrolls. We observe that, despite apparently ohmic behavior, the current collector impedance in cells with single- (or few-) tab arrangements tends to drive nonuniformity of current and electrochemical states throughout the jellyroll. This nonuniformity can give rise to enhanced and nonuniform lithium plating and other aging processes, depending on design and operating conditions.