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  1. 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.

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    Free, publicly-accessible full text available October 8, 2024
  2. Hands-on computing has emerged as an exciting and accessible way to learn about computing and engineering in the physical world for students and makers of all ages. Current end-to-end approaches like Microsoft MakeCode require tethered or battery-powered devices like a micro:bit, limiting usefulness and applicability, as well as abdicating responsibility for teaching sustainable practices. Unfortunately, energy harvesting computing devices are usually only programmable by experts and require significant supporting toolchains and knowledge across multiple engineering and computing disciplines to work effectively. This paper bridges the gap between sustainable computing efforts, the maker movement, and novice-focused programming environments with MakeCode-Iceberg, a set of compiler extensions to Microsoft's open-source MakeCode project. The extensions automatically and invisibly transform user code in any language supported (Blocks, JavaScript, Python)into a version that can safely and correctly execute across intermittent power failures caused by unreliable energy harvesting. Determining where, when, and what to save in a checkpoint on limited energy, time, and hardware budget is challenging. We leverage the unique intermediate representation of the MakeCode source-to-source compiler to design and deploy various checkpointing techniques. Our approach allows us to provide, for the first time, a fully web-based and toolchain-free environment to program intermittent computing devices, making battery-free operation accessible to all. We demonstrate new use cases with multiple energy harvesters, peripherals, and application domains: including a Smart Terrarium, Step Counter, and Combination Lock. MakeCode-Iceberg provides sustainable hands-on computing opportunities to a broad audience of makers and learners, democratizing access to energy harvesting and battery-free embedded systems. 
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