Nanotechnology has grown at an enormous rate for the past three decades, and recent advances in nanostructured materials and nanodevices have opened up new opportunities in a variety of applications, ranging from information and communication technology to healthcare and medicine. Herein, an overview of nanotechnology is given, describing the origins of the field, present technology, ongoing research, and future aspirations. In addition, the two possible methodologies of fabrication—the top‐down and bottom‐up approaches—are discussed, covering the merits and drawbacks of each approach. As an example of a top‐down procedure, the fabrication of electronic integrated circuits and the foreseen limitations of the procedure for further miniaturization are described. The bottom‐up approach, through self‐assembly and supramolecular chemistry, provides an exciting alternative route either combined with the top‐down approach or on its own.

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J. Phys. Chem. 1987,91, 3114-3116. Das in Kristallen von 1 die Magnesiumzentren koordinierende Ethanol stammt aus dem Stabilisator, der in kommerziellem CHCI, enthalten ist. Trotz der Bedeutung des Ethanols beim Zuchten der Kristalle hates bei diesen niedrigen Konzentrationen kaum einen EinfluD auf die in CH,CI,-Losung aufgenommenen Spektren. Kristalle von 1 wurden aus CH,CI,/CHCI, (Sjl), die zur Auslosung der Kristallisation mit Hexan uberschichtet wurden, erhalten, wahrend 2 aus Toluol/ CH,CI, (4/1) kristallisierte. Ein rosapurpurfarbener Kristall von 1, der auf eine GroOe von 0.13 x 0.20 x 0.60 mm3 zurechtgeschnitten wurde, und ein dunkelpurpurfarbener Kristall von 2 (0.017 x 0.06 x 0.17 mm') wurden zur Datensammlung auf einem Enraf-Nonius-FAST-Area-Diffraktometer rnit rotierender Mo-Anode (2 = 0.71073 A) nach bereits beschriebenen Verfahren verwendet (W. R. Scheidt, I. Turowska-Tyrk, Inorg. Chem. 1994, 33, 1314-1318). -Strukturanalyse von 1: a =12.176(1), b = 21.657(5), c = 29.302(8) A, p = 99.94(1)", monoklin, Raumgruppe P2,, V =7610.9(3) A3, Z = 4 (Dimere), pbei. =1.291 gem-,, 20,,, = 27.06". -2 : a =10.280(4), b =11.681(3), c =13.939(6), c( = 83.93(2), fl = 83.63(3), y =78.18(3)", triklin, Raumgruppe Pi, V=1622.2(10)A3,Z= 2,pbe,, =1.344g~m-~,20,,, = 29.73".-AlleMessungen wurden bei 124+2 K durchgefiihrt. Auf die Daten wurden Lorentz-, Polarisations-und Absorptionskorrekturen angewendet (relative Transmis-

Nature provides mechanisms that are able to dynamically control specific and nonspecific interactions between cells and biological surfaces [1,2]. Scientists have long tried to reproduce these dynamic biological events and have recently made an important step in that direction by creating artificial stimuli-responsive surfaces [3][4][5][6][7]. These smart substrates present modulatory surface properties that are able to respond to external chemical/biochemical [8][9][10][11][12], thermal [13][14][15], electrical [16][17][18][19][20], and optical stimuli [21][22][23][24][25][26][27][28][29][30][31]. Due to their dynamic nature such substrates are very appealing for applications in the biomedical field [32]. Progress to date has led to control over biomolecule activity [33] and immobilization of a diverse array of proteins, including enzymes [34] and antibodies [35]. These prior achievements have encouraged researchers to take the challenge of using dynamic surfaces to modulate larger and more complex systems, such as bacteria [36] and mammalian cells [37].Achieving control over surface properties could provide new insights in the understanding of cell behavior and can offer distinct benefits with regard to the development of medical devices. For instance, the modulation of cell attachment and detachment could lead to the prevention of unwanted bacteria fouling on implants, reducing the risk of infections and rejection [38][39][40][41][42]. Furthermore, dynamic surfaces able to present on demand regulatory signals to a cell could provide unprecedented opportunities in studies of cell responses in real-time. Cells in tissues adhere to and interact with their extracellular environment via specialized cell-cell and cell-extracellular

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Gold‐Nanokristalle, stabilisiert durch Thiole, die kovalent mit einer Kronenethereinheit verbunden sind, wurden auf das Erkennen und die selektive Bindung von Dibenzylammoniumionen in Lösung programmiert. Das Ergebnis ist ein Selbstorganisationsprozeß an der Nanokristalloberfläche unter Bildung eines Pseudorotaxans (siehe Bild).

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