EDI T O R I A L Open Access Special issue on nanofluids Stephen US Choi 1 , Yogesh Jaluria 2 , Oronzio Manca 3 , Liqiu Wang 4* NanofluidsLiqiu Wang, Yogesh Jaluria, Stephen Choi and Oronzio Manca Editorial Nanofluids, or fluid suspensions of nanometer-sized structures, are research challenges of rare potential but daunting difficulty. The potential comes from both scientific and practical opportunities in many fields. The difficulty reflects the issues related to multiscales. Nano- fluids involve at least four relevant scales: the molecular scale, the microscale, the macroscale, and the system- scale. The molecular scale is characterized by the mean free path between molecular collisions, the microscale by the smallest scale at which the law of continuum mechanics applies, the macroscale by the smallest scale at which a set of averaged properties of concern can be defined, and the systemscale by the length scale corre- sponding to the domain of interest. By their very nature, research and engineering p ractice in nanofluids are aimed at enhancing fluid macroscale and system-scale properties through the manipulatationof microscale physics (structures , properties and activities). Therefore, the success of nanoflu id technology depends very much on how well we can address issues such as effective means of microscale manipulation, interplay among physics at different scal es, and the optimization of microscale physics for the optimal macroscale and system-scale properties. The present special issue is dedicated to the latest advances in addressing these issues. The objective is to promote interdisciplinary research on nanofluids and motivate the nano community, which is uniquely quali- fied to make valuable contributions, to become more involved in this field of research and development. We would like to express our sincere appreciation to the contrib uting authors and review ers who have main- tained the standard associated with Nanoscale Research Letters. We are also thankful to Professor Zhiming Wang, the Editor-in-Chief, for providing this forum to discuss this emerging field. Author details 1 Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607 USA 2 Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8058, USA 3 Dipartimento di Ingegneria Aerospaziale e Meccanica, Seconda Universita’ degli Studi di Napoli Real Casa dell’Annunziata, Via Roma 29, Aversa (CE) 81031, Italy 4 Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Received: 17 January 2011 Accepted: 25 January 2011 Published: 25 January 2011 doi:10.1186/1556-276X-6-99 Cite this article as: Choi et al.: Special issue on nanofluids. Nanoscale Research Letters 2011 6:99. Submit your manuscript to a journal and benefi t from: 7 Convenient online submission 7 Rigorous peer review 7 Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within the fi eld 7 Retaining the copyright to your article Submit your next manuscript at 7 springeropen.com * Correspondence: lqwang@hku.hk 4 Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Full list of author information is available at the end of the article Choi et al. Nanoscale Research Letters 2011, 6:99 http://www.nanoscalereslett.com/content/6/1/99 © 2011 Choi et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2. 0), which permits unrestricted use, distribution, and reproduction in any m edium, provided the original work is properly cited. . journal and benefi t from: 7 Convenient online submission 7 Rigorous peer review 7 Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within. springeropen.com * Correspondence: lqwang@hku.hk 4 Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Full list of author information is available at the. I A L Open Access Special issue on nanofluids Stephen US Choi 1 , Yogesh Jaluria 2 , Oronzio Manca 3 , Liqiu Wang 4* NanofluidsLiqiu Wang, Yogesh Jaluria, Stephen Choi and Oronzio Manca Editorial Nanofluids,