Self-sustainable Computational Material Stickers
Weiser’s vision of ubiquitous computing promises the proliferation of trillion IoT devices by the year 2035. It brings into focus the research question as to how everyday objects and surfaces can be augmented or manufactured with computational capability without losing their form factor or affordance? Current smart objects (e.g., smart home control, smart fridge) look distinctively different from artifacts of daily use such as a paper sticky note, a cup, or a chair. They have hard bulky bodies, use rigid structural elements with millions of electronic components, and have a power budget that necessitates the maintenance of a wired connection or a bulky toxic battery.
Figure 1: Design Parameters and application architecture for self-sustainable computational material stickers
Truly blurring the distinction between digital and physical worlds requires balancing an artifact’s computational functionality with three other factors (Figure 1A): 1) power; 2) form factors that look and feel more like everyday objects; and 3) the cost of materials and ease of manufacturing (e.g., simple circuitry). Balancing all four together is a hard system design challenge.
Taking these design constraints into account, in my Ph.D. thesis work, I have focused on the development of computational material that can perform functional computing tasks like sensing, communication, actuation in an ultra-low-power budget which can be ambiently energy harvested. Moreover, such computational materials are manufactured cheaply and employ minimal electrical components. Specifically, I have built self-sustainable (battery-less) computational-material stickers that can be augmented onto physical objects and surfaces to support interesting interaction, human health, and infrastructure monitoring applications (Figure 2)
My research goals include: (1) Selection of materials and fabrication methods that can be employed to create flexible thin devices (aka. electrical components) for different computational functionalities and operate in low-power. (2) Building no or ultra-low-power computational circuits that show the promise of being printable and cheaply manufactured like a sticky note and have functionalities that can support data collection and user feedback. (3) Exploration of application scenarios for computational material sticky note where its battery-less, thin form factor are leveraged.
Research Methods: When power, form factor, and cost are considered system design constraints, generally, no commercially available functional devices (aka. electrical components) can satisfy the requirements. Thus, building self-sustainable computational-material stickers requires starting at the bottom of the application architecture (Figure 1B) by first selecting materials, employing the right fabrication techniques to build the functional devices, creating low-power circuits on a flexible substrate, and then finally using traditional ubicomp/HCI techniques of deploying the system in the application context and performing usability testing. I have adopted a broad research mindset spanning across different fields where I have learned the language and skills of a new field or created collaborations with experts in those fields to accomplish the research goals of self-sustainable computational-material stickers.
I have adopted an iterative approach towards building self-sustainable stickers, where I have created prototypes with increasing computational functionality. Each functional component added to the system individually imbibes the form factor, power, and cost design parameters (Figure 3). I will demonstrate that wrt. four projects — SATURN, ZEUSSS, MARS, and Venus (in-progress).
I first started by building thin and flexible sensors, e.g., a self-powered paper microphone – SATURN (Self-powered Audio Triboelectric Ultra–thin Rollable Nanogenerator), and more recently created novel design for ID, direction, and touch-based human interactions using simple everyday materials like paper, plastic, and copper (Figure 3A). Next, I combined SATURN (or any self-powered sensor) with just one transistor and antenna to build ZEUSSS (Zero Energy Ubiquitous Sound Sensing Surface)(Figure 3B left). ZEUSSS sticky note allows for wireless sensing of sound using backscatter communication from one tag at a time with no active power requirement. MARS stickers (Multi-channel Ambiently–powered Real-time Sensing)(Figure 3B right) extends this idea by employing a novel hardware sticker design consisting of just two transistors and seven passives components that consume nano-watts of power for multi-channel sensing. MARS interface stickers are 2x and 20x respectively lower in power and number of components than state of the art, and thus create a future opportunity for simultaneous sensing by printed stickers deployed on everyday surfaces. Powered by the heat of the user’s finger or a single photodiode in office lighting the MARS stickers can be leveraged as interaction and activity sensing widgets — buttons, sliders, microphones. Figure 2A showcases indoor scenarios where battery-free, rich-input sensing and multi-channel operations are best utilized. MARS wireless sensing stickers can be extended to add actuation. I further develop this in my new project Venus (in progress) through exploration of a flexible thermoelectric generator and electrochromic displays (Figure 3C, D). Novel material devices and systems developed during my Ph.D. can be further extended for self-sustainable human and structural health monitoring (Figure 2 B,C). In the future, I also plan to focus more on the human aspects, e.g., usability, privacy for self-suitable stickers.
In conclusion, my dissertation research focuses on building computational components from the ground up and combining them into application-oriented systems in a fundamentally different way than the traditional Ubicomp system research, where the focus was on building things from off-the-shelf components. These projects are meant to inspire multidisciplinary, out-of-the-box thinking for a new direction for computing – the Internet of Materials, where computing is woven into the ‘very fabric of our lives‘. I have also bolstered creating a highly multidisciplinary research community during my Ph.D. to push this ambitious research agenda.