Human-Computer Interaction Institute
School of Computer Science, Carnegie Mellon University


Computational Infrastructure Materials for
the Networked & Interactive Built Environmen

Sai Swaminathan

August 2022

Ph.D. Thesis


Keywords: Human-Computer Interaction, Ubiquitous Computing, Digital Fabrication, Computational Materials, Self-power, Low-power, Sensing, Actuation, 3D printing, Accessibility

From roads to roofs, homes to high-rises, my inspiration is the promise of building cyber-physical infrastructure for human interaction and enabling smart city applications. Unfortunately, there are several challenges in achieving this vision, due to the end of Moore's law, Dennard scaling, and our limited views on how computing systems are manufactured. To date, device manufacturing has focused primarily on miniaturization–packing the most functionality in the smallest form factor, despite our physical infrastructure being much larger in scale. We need to think creatively, design devices in new form factors (made in structural forms like walls, tables, facades, etc.) and materials of various kinds (e.g., those with extreme mechanical strength) that make up our built environments. There remain several challenges at the nexus of device power, form factor, and scale for designing our cyber-physical infrastructure.

In this dissertation work, I introduce "computational infrastructure materials" that enable us to build energy-efficient sensing, actuation, and communication in networked physical infrastructure (e.g., buildings, sidewalks) forms. Specifically, I look at how to enable our infrastructure materials (e.g., concrete, wood, composites) to do computation: (1) as they bear large force (~4000 lbs) (2) enable battery-free sensing and activity recognition at long distances (~70km), (3) actuate large-structures in response to user interaction, and (4) enable battery-free wireless communication. Additionally, I offer insights from the field about developing and deploying multi-modal tactile guidance surfaces. They contribute to an understanding of how computational infrastructure materials can support application areas such as accessibility.

Taken together, the capabilities introduced this thesis enable a range of applications in the built environment, such as digital buildings, accessibility, and ultimately towards creating sustainable and resilient cyber-physical infrastructure for human interaction. Finally, I summarize the contribution of this thesis and propose several future research efforts.

162 pages

Thesis Committee:
Scott Hudson (Chair)
Mayank Goel (HCII/ISR)
Lining Yao
Gregory Abowd (Northeastern University)
Haeyong Noh (Stanford University)

Jodi Forlizzi, Head, Human-Computer Interaction Institute
Martial Hebert, Dean, School of Computer Science

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