Nano is big at Purdue


By John R. Weaver, Birck Nanotechnology Center, Purdue University

The Birck Nanotechnology Center (BNC) building at Purdue University was dedicated on October 8, 2005. More than half the equipment has been installed, and research is now being performed in the facility. Researchers are working on projects to extend our knowledge of materials at the nanoscale and to create novel structures and devices. By October 2006, all of the equipment-183 major items-will be installed and operational in the 186,000-square-foot building.

The Birck Nanotechnology Center, located in Discovery Park at Purdue University, has an appealing façade and an open design that fosters the interaction of researchers working in the facility. Photo courtesy of HDR Architecture/Steve Hall (c) Hedrich Blessing.
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There are currently many very interesting research projects underway in the facility, with the emphasis being on collaborative, interdisciplinary research. Physics professor Ron Reifenberger and chemical engineering professor Fabio Ribiero are working with staff scientist Dr. Dima Zemlyanov on a number of studies. Ribiero is studying catalytic reactions on the nanoscale, while Reifenberger’s efforts are focused on conduction of individual molecules bonded to silicon substrates. Professor Rashid Bashir is leading a team of researchers in developing a “laboratory on a chip” that allows rapid detection of infectious organisms; professor Babak Ziaie is leading a team in developing an implantable device to monitor and control glaucoma; and Dr. Helen McNally is studying healing mechanisms of neurons in the spinal cord to determine ways of accelerating the healing of spinal-cord injuries.

The BNC facility consists of three major components: the laboratories, the cleanroom, and the human spaces. In designing the facility, the architect worked closely with the future occupants of the building to understand the needs of interdisciplinary, collaborative research in nanotechnology. Those needs led to a design that blends the roles of these three functional areas into a carefully engineered facility with each area complementing the others.

The laboratories are patterned after the NIH laboratory standard of 11-foot by 22-foot modules. The BNC contains 88 of these modules-some laboratories consisting of a single module and others configured from two-module labs to seven-module labs. Some systems, such as scanning electron microscopes, are better suited for a separate module where lighting and temperature can be controlled independently from surrounding equipment. In most cases, however, the advantages of collaboration lead to multiple-module laboratories.

All of the laboratories are designed to control temperature and electromagnetic interference (EMI), with the first-floor laboratories-half of the 88 modules-also designed to control vibration. Temperature control in all laboratories is within one degree centigrade and EMI is less than 0.1 milligauss. The first-floor laboratories meet the NIST A vibration standard as well. A special laboratory, the Kevin G. Hall Nanometrology Laboratory, controls all three of these parameters to a more precise level. There, temperature is controlled within 0.1°C, EMI is less than .03 milligauss, and vibration meets the NIST A-1 standard.

Electrical distribution and grounding were two major considerations in the laboratory design. The electrical distribution system uses an independent isolation transformer providing “clean” power to each laboratory, with a single isolation transformer providing “dirty” power to each laboratory wing. This keeps the power sources for instruments separate from the power sources for support equipment. The grounding system supplies an instrument ground to each laboratory separate from the power-supply ground. This grounding system is carefully designed to eliminate any ground loops in the facility.

To the rear of each laboratory area is a service galley that contains the utilities supplied to the laboratories as well as support equipment servicing the research instruments, such as vacuum pumps and chillers. This independent galley allows the services to each laboratory to be reconfigured in a short time and at a minimum cost, greatly enhancing the flexibility of the facility.

To foster collaboration, the laboratories are organized by technology, rather than by department or principal investigator. For example, atomic force microscopes (AFMs) from physics, mechanical engineering, and biology all share the same laboratory, allowing faculty and students to learn from accomplishments in other disciplines. This approach is already promoting increased information-sharing among the researchers.

The 25,000-square-foot cleanroom, called the Scifres Nanofabrication Laboratory, consists of a semiconductor-style nanofabrication cleanroom and a pharmaceutical style biocleanroom. Although these two cleanrooms are contained in the same envelope, they have different design features, separate airflow paths, and separate gowning and operational protocols, allowing pharmaceutical manufacturing cleanliness levels to be maintained in the biocleanroom while semiconductor cleanliness levels are sustained in the nanofabrication cleanroom.

The laboratories in the BNC utilize glass in the exterior walls whenever practical, enhancing safety and protocol adherence, and adding to the open atmosphere that fosters collaboration. Photo courtesy of John Weaver.
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The nanofabrication cleanroom is a typical semiconductor-style, three-floor cleanroom with a subfab level, cleanroom level, and air-handling level. The cleanroom level is further subdivided into the air-distribution space above the terminal (ULPA) filters, the cleanroom itself, and the underfloor area for air return and utility distribution.

It is designed using a bay-chase concept, with large chases holding the mass of the equipment and smaller bays containing the exposed research materials. A few of the bays are larger to accommodate legacy equipment that cannot be located in the chase.

Entry into the nanofabrication cleanroom follows standard protocols: pregowning with shoe covers and bouffant caps; an air shower to the gowning area; top-down gowning in hoods, GORE-TEX jumpsuits, boots and gloves; and a second air shower to the cleanroom.

With these controls in place, an ISO Class 3 (Class 1) cleanliness level has been achieved in the six most critical bays; ISO Class 4 (Class 10) has been achieved in five bays; and the two least critical bays are ISO Class 5 (Class 100). Although most of the cleanroom is controlled to within ±1°C, the most critical bay, e-beam photolithography, achieves temperature control to ± 0.1°C.

The biocleanroom utilizes a three-tier structure as well, but with major modifications to the cleanroom interior to eliminate potential biological entrapment locations. The most dramatic modifications are the floor system and the chase sizes. The perforated floor system was replaced with solid tiles, then seamless PVC flooring was placed over the entire biocleanroom floor. This flooring was coved to the wall surfaces and sealed to the walls. The flooring is kept pristine: penetrations through the walls are allowed using special precautions but no penetrations through the floor are allowed. A special wall system that eliminates voids at the seams and a ceiling system that accepts the terminal filters complete the specialized interior.

The biocleanroom chases are small, used for air return and utility distribution only. Rather than mount the equipment into the chase, all equipment stands completely in the biocleanroom with space between the equipment and the wall to allow cleaning. The chases are designed to be readily cleanable as well, especially for the first three feet above the air input to eliminate locations where bacteria or other viable materials could reside.

Contamination control in the Birck Nanotechnology Center goes far beyond the cleanroom. Gas distribution-bulk gases as well as specialty gases-are distributed in stainless-steel piping systems that are welded using ultrapure methods and are certified to part-per-billion (ppb) levels for contaminants such as oxygen and moisture. Particulate filtration rated at 30 nanometers ensures that particle levels are controlled as effectively as other impurities.

The laboratories and cleanroom are supported by an ultrapure water system that produces 12,000 gallons per day of SEMI E-1.2 water for both nanofabrication and biological research. Oxygen levels are below 1 ppb and total oxidizable carbon (TOC) levels are below 275 parts per trillion (ppt). The concentration of boron, the most loosely bound ion and therefore the most sensitive measurement of ionic impurities, is below the detectable limit of 5 ppt. The zero-dead-volume distribution loop is made of polyvinylidene fluoride (PVDF) piping, a very stable and inert plastic that inhibits bacterial growth and allows a joining method that minimizes entrapment areas and low-velocity sites. With a recirculation flow rate of 100 gallons per minute, it is carefully designed to keep high velocities of water flowing at every point in the loop.

A key design feature of the facility is its focus on safety. Using designs and protocols developed for the semiconductor manufacturing industry as a baseline, the Birck Nanotechnology Center has stressed safety in all research disciplines. From doubly contained piping with sophisticated leakage detection systems in the hazardous gas piping to safeguards in the use of biological agents, all facility hazards are evaluated and the appropriate controls applied. A full-time safety manager for the facility oversees these programs.

Dr. Dmitry Zemlyanov explains the x-ray photoluminescence system to National Science Foundation nanotechnology expert Mikhail Roco. Also pictured Birck Facility Manager John Weaver (far left) and Research Development Manager Dr. George Adams. Photo courtesy of Purdue University News Service.
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The Birck Nanotechnology Center is located in Discovery Park, a portion of the Purdue campus that has been specifically created for collaborative, interdisciplinary research in a variety of areas. In addition to fostering collaboration within the center, the location of the BNC in Discovery Park fosters collaboration between centers. This is exemplified in the collaborative work and physical connection between the Birck Nanotechnology Center and the Bindley Biosciences Center. The two facilities are connected by an enclosed walkway, and individual faculty members utilize laboratories in both facilities.

The Birck Nanotechnology Center is enabling Purdue University to move forward in nanotechnology research at an astounding rate. Recently hired faculty join with long-term Purdue faculty to leap beyond the previous levels of knowledge in this exciting field. Other Discovery Park centers, such as the Burton D. Morgan Entrepreneurial Center, are assisting in bringing products to market based on this research. Work at this new facility is already having an impact on our future.

John R. Weaver II serves as the facility manager for the Birck Nanotechnology Center at Purdue University. He is responsible for the facility infrastructure, safety and training activities, and cleanroom and laboratory operations. He can be reached at (765) 494-5494, or via e-mail at