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Wearables are becoming increasingly useful, primarily due to their activity-monitoring features that enable various healthcare applications. Everyday devices like smartwatches, however, often have complex ecosystems and convoluted interfaces. These devices need constant charging and can be difficult to use, cumbersome for users interested in only simple applications. As an alternative, simpler everyday wearable, we present Hapt-Aids, self-powered on-body tags that passively monitor user activities and deliver haptic notifications. Our small-footprint devices 1) harvest energy from activity-specific sources, 2) use this energy as sensor information, and 3) convert this energy into haptic actuation using only analog hardware, without digital components or firmware. This structurally simple, triple-purpose design makes our system extremely low maintenance while being cost- and energy-efficient, leading to a friendly user experience. We present our proof-of-concept system design: a custom, unique architecture formed through theoretical modeling and evaluation studies, and we build four demo applications. Through in-lab benchmark testing and user studies, we demonstrate the potential of Hapt-Aids as alternative low-cost, easy-to-use wearables. 

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. 

Automating operations of objects has made life easier and more convenient for billions of people, especially those with limited motor capabilities. On the other hand, even able-bodied users might not always be able to perform manual operations (e.g., both hands are occupied), and manual operations might be undesirable for hygiene purposes (e.g., contactless devices). As a result, automation systems like motion-triggered doors, remote-control window shades, contactless toilet lids have become increasingly popular in private and public environments. Yet, these systems are hampered by complex building wiring or short battery lifetimes, negating their positive benefits for accessibility, energy saving, healthcare, and other domains. In this paper we explore how these types of objects can be powered in perpetuity by the energy generated from a unique energy source - user interactions, specifically, the manual manipulations of objects by users who can afford them when they can afford them. Our assumption is that users' capabilities for object operations are heterogeneous, there are desires for both manual and automatic operations in most environments, and that automatic operations are often not needed as frequently - for example, an automatic door in a public space is often manually opened many times before a need for automatic operation shows up. The energy harvested by those manual operations would be sufficient to power that one automatic operation. We instantiate this idea by upcycling common everyday objects with devices which have various mechanical designs powered by a general-purpose backbone embedded system. We call these devices, MiniKers. We built a custom driver circuit that can enable motor mechanisms to toggle between generating powers (i.e., manual operation) and actuating objects (i.e., automatic operation). We designed a wide variety of mechanical mechanisms to retrofit existing objects and evaluated our system with a 48-hour deployment study, which proves the efficacy of MiniKers as well as shedding light into this people-as-power approach as a feasible solution to address energy needed for smart environment automation.