Advances in Multi‐Scale Pores and Channels Systems

“Pores” and “Channels” are everywhere, e.g, from small biological ion channels to large oil pipelines. Pores and channels can be distinguished by the relationship between their diameter and their depth. If the diameter is greater than the depth, the system is treated as pore, otherwise, channel. However, for established porous materials, including membranes, no such strict definition is used. Both, “Pores” and “Channels” have a wide range of significant applications in different scales. For example, pipelines which are commonly used in the chemical industry, food industry, agriculture, and petroleum transportation, can be regarded as macro-scale channels. Good examples of micro-scale channels can be found in microfluidics, which has a rapidly increasing impact in the areas of chemical synthesis, biomolecule and cell analysis, micro- and nanofabrication, and information technology, etc. With regard to the nano-scale, the nanochannels which led to the birth of a whole new area of research, can be used for nanofluidics, gas separation and storage, batteries, water purification, energy harvest and DNA sorting. In the past, such multi-scale pores and channels systems have been intensively explored and contributed to new developments in materials science, membrane science and technology, or in micro/nanotechnology for analytical, biomedical or information processing applications. Stimulated by the achievements and the even larger potential of multi-scale pores and channels systems, increasing research activities are devoted to important aspects such as energy saving, anti-fouling, anti-corrosion, and anti-blocking functionalities, switchability and controllability, integration of various different functionalities, and good stability in such confined space. In this special issue, we aim to highlight the state of the art in the field and provide an overview of recent research in the area, including nanopores and nanochannels, nanofluidics, micropores and microchannels, microfluidics, and smart porous membranes, which all hold great promise in material science, engineering and life science. This special issue includes 3 reviews, 2 concepts and 14 research articles by scientists from Xiamen University, University of Valencia, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), King Abdullah University of Science and Technology (KAUST), Indiana University, Tokyo Institute of Technology, Kavli Institute of NanoScience, University of Florida, University of Notre Dame, Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences, Universitat Politècnica de Catalunya, Stanford University, Harvard University, East China University of Science and Technology, Sichuan University, CIC biomaGUNE, and Flerov Laboratory of Nuclear Reactions. The content of these articles covers a broad range of subjects in the area of multi-scale pores and channels systems, such as their preparation/fabrication or their utilization for nanomaterials processing, the advanced characterization and modelling, establishing various functions like stimuli-responsive or actively switchable pores or channels, as well as the implementation of (bio)chemical substance's sensing, analysis or catalytic conversion. We sincerely thank all the scientists who have contributed to this special issue. Without their great efforts, we could not achieve this. We also would like to express our appreciation to the editorial team of Small, especially Dr. José Oliveira and Dr. Lulu Ma. The team has provided professional support in organizing this special issue. Meanwhile, we are grateful to the State Key Laboratory of Physical Chemistry of Solid Surfaces of Xiamen University, China for financial support. The Laboratory was established in the late 1980's and is a leader in the areas of catalysis, electrochemistry, and structural and theoretical chemistry, as well as their interactions addressing relevant subjects in China. We hope that this special issue will be able to highlight the major developments in “multi-scale pores and channels systems” and inspire the active interest of more scientists to join in this field. Xu Hou received his B.Sc. degree (2006) from Sichuan University. He completed his Ph.D. (2011) at the National Center for Nanoscience and Technology, China, under the direction of Prof. Lei Jiang. He did postdoctoral research in Prof. Joanna Aizenberg's group at Harvard University (2012–2015). Now he is a full professor in both the College of Chemistry & Chemical Engineering and the College of Physical Science & Technology at Xiamen University, China. His research group mainly focuses on bio-inspired and smart multi-scale pore/channel systems, polymer materials, membrane science & technology, microfluidics, interfacial science, physical chemistry, electrochemistry, nano/micro fabrication for energy-saving and biomedical applications. Zuzanna S. Siwy received her Ph.D. in 1997 from the Silesian University of Technology, Gliwice, Poland, and habilitation in 2004. From 2000–2003 she was a Fellow of the Foundation for Polish Science, and the Alexander von Humboldt Foundation at the Institute for Heavy Ions Research (GSI) in Darmstadt, Germany. After conducting postdoctoral research at the University of Florida, Gainesville, in July 2005, Dr. Siwy joined the Department of Physics and Astronomy at the University of California, Irvine. In 2007, she became the Fellow of the Alfred von Sloan Foundation. Her current research interests focus on using synthetic nanopores as templates for biomimetic channels as well as ionic diodes and ionic transistors. Mathias Ulbricht received his Ph.D. degree in 1987 from Humboldt-University Berlin, Germany, and his habilitation from the same university in 1997. He also worked as a researcher at the Rensselaer Polytechnic Institute, Troy, NY (1992–1993), and the GKSS Research Center, Geesthacht, Germany (1997–1999). He was founder and CEO of a private company in Berlin (1999–2003). Since 2001, he is a full professor at University of Duisburg-Essen. His research interests are in the field of functional polymeric as well as nanohybrid materials and have a focus on synthetic membranes and membrane-based technologies for water purification, bio-separation and energy conversion.