We developed a novel two-photon polymerization (2PP) configuration for fabrication of high-aspect three-dimensional (3D) structures, with an overall height larger than working distance of the microscope objective used for laser beam focusing into a photosensitive material. This method is based on a modified optical 2PP setup, where a microscope objective (1003 high N.A.), immersion oil and cover glass can be moved together into the photosensitive material, resulting in an effective higher and wider objective working range (WOW-2PP). The proposed technique enables the fabrication of high-aspect structures with sub-micrometer process resolution. 3D structures with a height of 7 mm are demonstrated, which could hardly be built with the conventional 2PP set-up due to refractive index mismatch and laser beam disturbances.

Multi-focus two-photon polymerization with a spatial light modulator is demonstrated. The spatial light modulator generates multi-focus spots via phase modulation technique controlled by a computer generated hologram (CGH) pattern. Each focus spot can be individually addressed in position and laser intensity. The multi-focus two-photon polymerization technique allows the fabrication of complex 2-D and 3-D structures both symmetric and asymmetric. Smooth sine curved polymerized lines with amplitude of 5 microm and a period of 200 microm were obtained by fast switching of the CGH patterns.

No abstract

This paper describes methods for design, manufacturing and characterization of a micro-mechanical valve for a novel glaucoma implant. The implant is designed to drain aqueous humour from the anterior chamber of the eye into the suprachoroidal space in case of an elevated intraocular pressure (IOP). In contrast to any existing glaucoma drainage device (GDD), the valve mechanism is located in the anterior chamber and there, surrounded by aqueous humour, immune to fibrosis induced failure. For the prevention of hypotony the micro-mechanical valve is designed to open if the physiological pressure difference between the anterior chamber and the suprachoroidal space in the range of 0.8 mmHg to 3.7 mmHg is exceeded. In particular the work includes: (i) manufacturing and morphological characterization of polymer tubing, (ii) mechanical material testing as basis for (iii) the design of micro-mechanical valves using finite element analysis (FEA), (iv) manufacturing of microstent prototypes including micro-mechanical valves by femtosecond laser micromachining and (v) the experimental fluid-mechanical characterization of the manufactured microstent prototypes with regard to valve opening pressure. The considered materials polyurethane (PUR) and silicone (SIL) exhibit low elastic modulus and high extensibility. The unique valve design enables a low opening pressure of micro-mechanical valves. An ideal valve design for PUR and SIL with an experimentally determined opening pressure of 2 mmHg and 3.7 mmHg is identified. The presented valve approach is suitable for the inhibition of hypotony as a major limitation of today's GDD and will potentially improve the minimally invasive treatment of glaucoma.

Tetrarubidium‐und Tetracäsiumhexaphosphid werden beim quantitativen Umsatz der Elemente bei 870 K bzw. 920 K in Nb‐Ampullen erhalten. Beide Verbindungen sind schwarze Halbleiter (EG ≈ 1,3—1,6 eV), die Kristalle zeigen metallischen Glanz. Die Strukturen sind orthorhombische Defektvarianten M4P6□2 der hexagonalen AlB2‐Struktur mit planaren isometrischen P6‐Ringen als charakteristische Baueinheiten. Die Bindungslänge d(PP) = 215 bzw. 214 pm entspricht einem aromatischen 10° System mit einer über die sechs Bindungen delokalisierten Doppelbindung. Beim thermischen Abbau entsteht quantitativ M3P7. In Lösungen von Ethylendiamin disproportionieren die Verbindungen M4P6 in M3P7 und M3P. Intermediär treten im Tieffeldbereich von 31P‐NMR‐Spektren jeweils Singulett‐Signale auf (Δ(α‐K4P6) = 331; Δ(Rb4P6) = 337; Δ(Cs4P6) = 348), die dem valenztautomeren Hexaphosphen(4) zugeschrieben werden. Die inneren Schwingungen der P6‐Ringe wurden aus IR‐und Raman‐Spektren ermittelt. Für Cs4P6 liegen die Fundamentalschwingungen bei n̈(A1g) = 356 cm−1, n̈(E2g) = 507 bzw. 202 cm−1. Diese Abfolge entspricht derjenigen von Benzol. Mit semiempirischen LCAO‐MO Rechnungen wird gezeigt, daß in der Reihe P6n− mit n = 2, 4, 6 zwar das Anion P62− das stabilste ist, daß jedoch mit der Bildung eines M2[m̈‐(η6‐P6)]‐Komplexes die Einheit M2P62− wesentlich stärker stabilisiert wird als die übrigen Isomeren. Unter den Isomeren P64− ist das hexagonal‐planare 10°System um 7 eV stabiler als der isomere Bicyclus.