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Batteryless, energy-harvesting systems could reshape the Internet of Things into a more sustainable societal infrastructure. 

Whenever a user interacts with a device, mechanical work is performed to actuate the user interface elements; the resulting energy is typically wasted, dissipated as sound and heat. Previous work has shown that many devices can be powered entirely from this otherwise wasted user interface energy. For these devices, wires and batteries, along with the related hassles of replacement and charging, become unnecessary and onerous. So far, these works have been restricted to proof-of-concept demonstrations; a specific bespoke harvesting and sensing circuit is constructed for the application at hand. The challenge of harvesting energy while simultaneously sensing fine-grained input signals from diverse modalities makes prototyping new devices difficult. To fill this gap, we present a hardware toolkit which provides a common electrical interface for harvesting energy from user interface elements. This facilitates exploring the composability, utility, and breadth of enabled applications of interaction-powered smart devices. We design a set of energy as input harvesting circuits, a standard connective interface with 3D printed enclosures, and software libraries to enable the exploration of devices where the user action generates the energy needed to perform the device's primary function. This exploration culminated in a demonstration campaign where we prototype several exemplar popular toys and gadgets, including battery-free Bop-It--- a popular 90s rhythm game, an electronic Etch-a-sketch, a Simon-Says-style memory game, and a service rating device. We run exploratory user studies to understand how generativity, creativity, and composability are hampered or facilitated by these devices. These demonstrations, user study takeaways, and the toolkit itself provide a foundation for building interactive and user-focused gadgets whose usability is not affected by battery charge and whose service lifetime is not limited by battery wear. 

The increase of distributed embedded systems has enabled pervasive sensing, actuation, and information displays across buildings and surrounding environments, yet also entreats huge cost expenditure for energy and human labor for maintenance. Our daily interactions, from opening a window to closing a drawer to twisting a doorknob, are great potential sources of energy but are often neglected. Existing commercial devices to harvest energy from these ambient sources are unaffordable, and DIY solutions are left with inaccessibility for non-experts preventing fully imbuing daily innovations in end-users. We present E3D, an end-to-end fabrication toolkit to customize self-powered smart devices at low cost. We contribute to a taxonomy of everyday kinetic activities that are potential sources of energy, a library of parametric mechanisms to harvest energy from manual operations of kinetic objects, and a holistic design system for end-user developers to capture design requirements by demonstrations then customize augmentation devices to harvest energy that meets unique lifestyle.