This project integrates remote sensing  into building materials and propose a new form of user interface (UI). Project developed by Jorge Cruz and Anthony Samaha, NJIT ’16 with supervision by Andrzej Zarzycki, NJIT. Top image shows transparent PCBs by Anthony Samaha.

For the in-depth discussion on these projects see: Embedded Building Components: Prototyping with Emerging Technologies paper published/presented at eCAADe 2017 Conference. It can be accessed via CuminCAD and ResearchGate portal.

INTRODUCTION
The introduction of capacitive sensing into construction assemblies allows for greater integration of building materiality and enhanced user interaction without making technology visually explicit or dominant. It extends the user interface (UI) qualities present in everyday objects into the building itself and opens new possibilities for architecture and the ways users interact with it. This presents an important aspect of new embedded architectural systems, with potential for designers to use various building materials and assemblies not only for sensing and actuation but also as controls and UI. Since these controls can be seamlessly integrated into the materiality of architecture, they can function in less explicit ways and on an as-needed basis, leading to further virtualization of materiality in architecture. The design benefits of using capacitive sensing in building assemblies come from the ability to integrate sensor pads within the base material: hiding electrodes and allowing finish materials to maintain their uninterrupted visual presence as well as protecting sensors and electrodes from the impact of an outside environment. The depth of encapsulation and the effect on capacitance can be controlled by the size of the capacitive surface.

SENSING AS INTERFACING
Distributed sensor and actuator systems provide an opportunity for data collection that can be used for building management, performance analysis, and real-time interconnection with other devices and appliances. Many of the sensors that are deployed in monitoring buildings and tracking users could also function as a form of user interface (UI). This dual approach not only allows for buildings to respond to human activities but also provides opportunities for users to interact with them intentionally.

An integration of capacitive sensing into ceramic tiles. Physical prototype developed by Jorge Cruz, NJIT’16

The Hidden Touch Interface project (video below) looked into an integration of capacitive sensors into various building materials, both as an explicit interactive element and as a hidden functionality. Philosophically, the project was looking at both conscious and unconscious computer-human interaction, and ways both could be used and interconnect. Touch is a type of interaction that can be intentional (conscious) as well as unintentional (unconscious).

COMPONENTS
The Hidden Touch Interface prototype utilized an MPR121 capacitive sensor controller module driven by an I2C interface on ESP8266 (below). The chip can control multiple individual electrodes. Electrodes and connecting wires have a certain amount of inherent capacitance that is balanced against user-induced
capacitance.

Components used for capacitive material interface.

The convenient part of this system is that electrodes can be (1) nonmetallic as long as they are
electrically conductive, (2) connected with only a single wire, (3) concealed under any nonmetallic materials, (4) used to detect objects centimeters away, and (5) inexpensive. This allowed the Hidden Touch Interface project to test a wide range of building materials, from wood and ceramic/stone tiles to acrylic, glass, and mirror (below). Depending on the types of resistors used, direct touch or just proximity could be implemented in both on-surface and under-the-surface arrangements.

Testing various materials as the capacitive interface. Prototypes by Anthony Samaha and Jorge Cruz, NJIT

Capacitive sensors can be made from variety of different media, such as copper, aluminum, indium tin oxide (ITO), or printed conductive inks. Metallic capacitive sensors can be implemented on surfaces of solid and flexible materials, extending the range of possible design applications. Capacitive sensing works effectively through various nonconductive materials, even relatively thick ones, that do not ground the charge present when an object or a person interacts with sensor pads. ITO-based electrode pads allow the capacitive sensor to be up to 90% transparent, providing yet another important design opportunity. This approach is commonly implemented in touch screens. However, the same technology could be integrated into building assemblies using ITO-coated glass and films to provide extended sensing opportunities as well as using electrically conductive properties of ITO to support various actuation needs. A common example could be combining capacitive-sensing UI with digital displays or illumination. Integration of multiple functionalities into a conductive capacitive surface would require a careful study of the electrode sizes and spacing to maintain the optimal sensor performance. Since indium is a rare metal, which most likely would prevent its large-scale application in the building industry, there is a line of research that looks at replacing it with other materials while maintaining conductive properties .