During discussions and study of the nano-to-meter-scale building concept two different approaches have emerged. The basic difference is in the control of the building process. One is a more typical engineering, mechanistic approach with extrinsic control and instruction passing, the other is using intrinsic programming of bionanorobots. So far we mainly worked on the extrinsic control.

A top-down concept has been developed following certain suppositions, which are closely related to our motivation to increase productivity, reduce waste, pollution and energy consumption caused by traditional building technologies. The first supposition therefore was to use materials that exists on site and can be transformed into building materials at the nano level. Carbon nanotubes have extraordinary characteristics, which can be varied using today's production nanotechnologies. The next supposition, therefore, was to use carbon as the basic material. As carbon exists in nature in vast amounts, the next supposition was to extract it from CO2 from the air. The building process is to be executed on the nano level using active nano devices that shall be controlled extrinsically using a detailed Building information model (BIM) as the source of all necessary information.

The defined suppositions brought us to the following conceptual solution:
  1. The fundamental building process is taking part at nano level by multifunctional nanodevices (nanorobots), which are capable of 
    • capturing CO2 from the air and extracting C molecules from it, releasing O2 back into the air, and
    • building 3D carbon nanotube arrays with characteristics required for a specific area (strength, conductivity, colour, transparency etc.)
  2. Nanorobots are controlled and powered externally by light; instructions are coded using specific wavelengths.
  3. Light is emitted by a projector installed above the site. To avoid interference with light emitted by other sources, an adequate wavelength spectrum has to be chosen.
  4. The projector is using the detailed BIM model as input, and transmits continuously the horizontal crossection, going from the bottom to the top height of the model - see Figures C1 and C2.
  5. Openings of the final model are temporarily filled with carbon nanomaterial, which transforms back into CO2 after a specific time period (or under specific conditions), when its function as a supporting structure is fullfiled.
  6. All utilities and coatings (if necessary) are built at the same time, together with the bearing structure (e.g. pipelines, power lines, communication lines), and are part of the building.

The building process consists of the following steps:
  1. Designing a detailed BIM model with all necessary utilities and coatings, as well as temporary fillings (these can be added automatically after the building model is finished by following the rule that every part of the structure has to be vertically supported down to the base level).
  2. Site preparation (excavation, projector installation).
  3. Deploying nanorobots onto the maximal extent of the building layout.
  4. Starting the process by continuously emitting instructions (represented as specific light wavelengths) to build 3D CNT arrays with required characteristics, until the top of the building is reached.
  5. After the light is off for a certain time, the nanorobots stop to function permanently, thus preventing any unwanted activity after the process is finished.
The load bearing material is in function instantly, therefore the temporary supporting material can dissolve after the building is finished. It dissapears off the building in the form of CO2 gas (e.g. from rooms, niches, pipelines and any other holes). With this the building is finished. With transparent CNT even windows could be "built-in" during the process, as well as some further equipment. It is, however, too early to explore in such detail all the effects of nano- to meter-scale building.