PITAS: Sensing and Actuating Embedded Robotic Sheet for Physical Information Communication
This work presents PITAS, a thin-sheet robotic material composed of a reversible phase transition actuating layer and a heating/sensing layer. The synthetic sheet material enables non-expert makers to create shape-changing devices that can locally or remotely convey physical information such as shape, color, texture and temperature changes. PITAS sheets can be manipulated into various 2D shapes or 3D geometries using subtractive fabrication methods such as laser, vinyl, or manual cutting or an optional additive 3D printing method for creating 3D objects. After describing the design of PITAS, this paper also describes a study conducted with thirteen makers to gauge the accessibility, design space, and limitations encountered when PITAS is used as a soft robotic material while designing physical information communication devices. Lastly, this work reports on the results of a mechanical and electrical evaluation of PITAS and presents application examples to demonstrate its utility.
The field of soft material-based actuators and shape-changing interfaces is young, yet rapidly growing. It has taken root to broaden supporting mechanisms and technologies, inspiring much cross-domain research. Although shape-changing interfaces can support adaptive, flexible interactions within unpredictable real-world environments, one long-standing challenge is the lack of rapid prototyping methods that can be used to create such interfaces. Making soft robotic materials that can sense, self-actuate, and produce large macroscopic deformations requires a considerable amount of technical setup, which further limits the system designs from being compact and narrows the range of applications for untethered systems. In addition, applying sensing capabilities to hyper-elastic elastomeric matrices requires expensive machine setups or complicated fabrication steps (e.g., directly 3D printing embedded strain sensors or creating micro-channels filled with conductive liquid metal for pressure sensors).
To overcome these challenges, we present PITAS, a "robotic material" sheet, consisting of a sensing/heating layer and an actuation layer. When heated, the ethanol embedded in the actuation layer boils once it has reached the liquid-gas transition temperature, leading to a volumetric expansion, but does not require external regulating systems, and will reverse back to its original shape as its temperature returns to ambient levels. The goal of this paper is to present a rapid and accessible prototyping method that can be used to create reversible soft-material-based systems.
PITAS integrates both input sensing and active shape output within a single sheet, and this soft silicone-based system endows PITAS with great adaptability to different materials (e.g., thermochromic pigments, tactile add-ons) for different purposes. Additionally, the bottom conductive layer makes PITAS system "heating ready", so one can simply attach electrodes selectively for different swell sizes or locations. The generic robotic sheet form factor and the associated cutting fabrication approaches further enable applications ranging from making 2D-3D shape-changing artifacts to augmenting everyday objects. Within the wide range of applications, PITAS can also go beyond a single space to convey physical information across multiple locations. Prior work has demonstrated that materiality plays a critical role in emotional interactions -- how we perceive, interpret, and feel about information. So, we also investigate how non-expert makers could create their own physical telecommunication devices, as well as explore the unique and feasible affordances PITAS can provide.
Although PITAS is a custom synthetic sheet that was prepared in the lab, it would be possible to mass-produce the sheets to make them widely available in electronics or craft retail stores, especially given the simplicity of the sheet fabrication process. Like copper tape or other craft sheet materials, those who enjoy DIY-making projects could purchase a roll and use it as needed, apply widely available cutting methods, and connect it with existing electronics and hardware parts for self-sensing and actuating projects.