Nanotechnology has been aptly described as the science of building a structure one atom at a time. First widely applied in computer science, nanotechnology has also shown great promise as the basis of novel drug-delivery systems. As a result, many laboratories are planning to incorporate specialized nanoscale R&D and/or nanofabrication facilities (Figure 1).
Certain areas of nanoresearch and fabrication require a hyper-clean environment, with a certification ranging from Class 10,000 to Class 10 depending on the process involved. Therefore, the design of these facilities must support self-contained cleanroom facilities, that is, prefabricated or semiprefabricated 10- to 12-ft-tall structures with built-in high-efficiency particulate air (HEPA) filtration systems.Within a laboratory facility devoted to nanotechnology research, there are typically numerous “conventional” research and support laboratories; however, the heart of a nanotechnology facility is usually the certified cleanroom suite, where the most exacting experimentation and fabrication occur. These certified cleanrooms may comprise anywhere from 20 to 30% or more of the overall area of a nanotechnology laboratory. At an average construction cost of $600 to $1200 per square foot (generally at the high end of that range), certified cleanroom suites are a significant investment (Figure 2).
Figure 1 - Nanofabrication activity in a cleanroom facility at the Boston University Photonics Center, Boston, MA.
Figure 2 - Nanofabrication cleanroom space at the University of Florida Physics Building, Gainesville, FL.
Vibration isolation
In nanoresearch and fabrication facilities, space planning and vibration control are key issues. The cleanroom suite should be located away from heavily trafficked corridors, elevators, major mechanical spaces, and exterior facades of the building adjacent to busy streets. Moreover, a heavy, rigid structural system for the zones where nanoscale activities occur should be designed to control vibration to a 1000- microinch level or less. This parameter can be critical to the success of the facility, and it is very important that the designer understand the researchers’ critical requirements in this regard. Therefore, slab on grade construction can be ideal. If the nanotechnology spaces are on elevated floor levels, consideration may be given to a separate structural grid below to carry heavy systems that may cause vibration, such as steam piping or large water lines. Additional measures to control vibration include providing air gaps between perimeter partitions of the nanotechnology space and other surrounding walls and the use of slab isolation and low-velocity ducts.
Controlling airflow
Precise control of airflow is crucial to maintaining a hyper-clean environment. The mechanical system must be designed both to deliver a high volume of air at low velocity through the HEPA filtration system in the ceiling of the cleanroom suite and to create a laminar flow through the room. The air flows straight down to “wash down” any ambient particles generated by people and activities in the space, and is then evenly exhausted through an exhaust system in the cleanroom floor or at floor level around the perimeter.
Providing adequate space for these large air ducts above the 10- to 12-ft-high cleanroom construction typically requires a minimum 18-ft floor-to-floor height, within which the modular or semimodular cleanroom suites can be constructed. In some cases, this interstitial space is designed with access points and catwalks to allow maintenance activities to occur without physically entering the cleanrooms. All penetrations into the cleanrooms through the walls, floor, or ceiling must be carefully sealed.
Ancillary spaces
Figure 3 - A researcher checks set up in a cleanroom facility at the Boston University Photonics Center, Boston, MA.
One of the contributing factors to the high cost of these facilities is the need for specialized support spaces. These include vestibules, changing rooms and lockers, and corridors housing a series of increasingly clean spaces—from Class 10,000 to Class 1000 to Class 100 maintained with a positive air-pressure cascade—through which scientists and technicians travel on their way to the sequentially cleaner spaces. These ancillary spaces may also include areas in which staff are washed by air showers.
For security purposes, proper location and controlled access are also critical. In order to maintain strict control of the specialized environment, cleanroom suites should be located in a facility area that is remote from the public, as well as unauthorized staff, and protected by electronic access security systems.
Lighting is another important design consideration. Some nanofabrication operations (Figure 3), such as photolithography, are extremely sensitive to certain light wavelengths; thus lighting within the space and observation windows into the space must be carefully filtered to screen out undesirable wavelengths.
Location, location
Given these considerations, a basement or interior ground floor location is often the least expensive place to locate the cleanroom suite. However, if the cleanroom suite is part of the core laboratories supporting the R&D activities of a number of scientists across multiple disciplines, researchers will generally prefer that they be located convenient to their primary research laboratories and offices. A cost-effective solution might lay in identification of a core zone with a very rigid structural design located in the center of the building and stacked vertically. Of course, in making this decision, the architect and owner must recognize that they may be compromising the future expansion capability of the specialized core facilities.
In selecting architects and contractors, laboratories need to require demonstrated expertise in the costeffective planning, design, and construction of hyperclean laboratories. Most contractors, for example, lack the appropriate experience and expertise to manage such a project and train workers in the processes required to construct these facilities, including the constant, vigilant attention to avoidance and cleanup of construction dirt and debris that can become embedded in the construction only to be dislodged into the air later after the cleanroom facility is operational. The design and construction of hyper-clean cleanroom suites involves a significant investment. Owners need to select professionals who can leverage their knowledge of developments in advanced research and technology into design and construction strategies that help laboratories remain competitive.
Mr. Harvath is Principal and Director, Science & Technology Practice, Cannon Design, One City Centre, Ste. 2500, St. Louis, MO 63101, U.S.A.; tel.: 314-241-6250; fax: 314-241-2570; e-mail: [email protected].