Search

Hybrid polymers constitute a class of optical materials combining properties of inorganic glass and organic polymers. The flexible synthesis and processing allows for specific tailoring of their properties as required for the fabrication of high-performance and reliable microoptical elements. While wafer-scale fabrication of microoptics using hybrid polymers is widely used in an industrial environment, they gain ever-increasing attention in additive manufacturing and 3D printing technologies. This chapter introduces the chemical concepts behind hybrid polymers, discusses their synthesis and processing, and gives a record on their application for the fabrication of microoptical and photonic elements using established wafer-scale as well as emerging additive manufacturing processes, in particular inkjet printing and two-photon polymerization direct laser writing.

We propose novel additive manufacturing processes to cost-effectively generate prototypes and small batches of hybrid micro-optical components. We combine UV-molding with inkjet printing techniques using the polymer inks InkOrmo and InkEpo designated for permanent optical applications. This enables the integration of diffractive and refractive optical elements into one monolithic micro-component and thus the implementation of tailor-made optical designs. Finally, the proposed processes allow a high versatile fabrication making individual micro-optics easily accessible.

A novel manufacturing chain to cost-effectively generate prototypes of hybrid micro-optical components is proposed. UV-molding and inkjet printing techniques are combined with the optical polymer inks InkOrmo and InkEpo for easily implementing tailor-made optical designs.

Nanoimprint lithography (NIL) is one of the most promising technology platforms for replication of nanometer and micrometer scale 3D topographies with extremely high resolution and throughput, as needed for e.g. photonic or optical applications. One of the remaining challenges of 3D NIL, however, is the fabrication of high quality 3D master originals – the initial patterns that are replicated multiple times in the NIL process. Here, we demonstrate a joint solution for 3D NIL where NanoFrazor thermal scanning probe lithography (t-SPL) is used to pattern the master templates with singlenanometer accurate 3D topographies. 3D topographies from polymer resist master templates are replicated using a HERCULES NIL system with SmartNIL technology. Furthermore, 3D patterns are transferred from the resist into a silicon substrate via reactive ion etching (RIE) and the resulting silicon master template is used for producing polymeric working stamps into OrmoStamp and, finally, replicas into optical grade OrmoClearFX material. Both replication strategies result in very high-quality replicas of the original patterns.

Edited by Reinhold Leinfelder, Alexandra Hamann, Jens Kirstein and Marc Schleunitz. Image Knowledge Gestaltung. An Interdisciplinary Laboratory. Cluster of Excellence at the Humboldt-Universität zu Berlin | Freie Universität Berlin. There are no simple solutions in the Anthropocene epoch. Every single person lives in a highly complex system and is connected to it by his or her actions. By focusing on the example of alimentation, this interconnectedness can be exposed and presented in a form that everyone can understand. Comics as a communication medium not only have the potential to make complex issues accessible in an appealing form; the comic-making process itself can inspire scientific work, and reveal new connections. This proceedings volume includes contributions on alimentation and comic theory by Jaqueline Berndt, Anne-Kathrin Kuhlemann, Toni Meier, Veronika Mischitz, Stephan Packard, Lukas Plank, Nick Sousanis, Katerina Teaiwa and Arnold van Huis. It is the result of the two-day symposium Science meets Comics, held in October 2015 in the Cluster of Excellence Image Knowledge Gestaltung. An Interdisciplinary Laboratory at the Humboldt-Universität zu Berlin, which discussed and developed these new means of communication in relation to alimentation.

The fabrication of optical interconnects has been widely investigated for the generation of optical circuit boards. Twophoton absorption (TPA) lithography (or high-precision 3D printing) as an innovative production method for direct manufacture of individual 3D photonic structures gains more and more attention when optical polymers are employed. In this regard, we have evaluated novel ORMOCER-based hybrid polymers tailored for the manufacture of optical waveguides by means of high-precision 3D printing. In order to facilitate future industrial implementation, the processability was evaluated and the optical performance of embedded waveguides was assessed. The results illustrate that hybrid polymers are not only viable consumables for industrial manufacture of polymeric micro-optics using generic processes such as UV molding. They also are potential candidates to fabricate optical waveguide systems down to the chip level where TPA-based emerging manufacturing techniques are engaged. Hence, it is shown that hybrid polymers continue to meet the increasing expectations of dynamically growing markets of micro-optics and optical interconnects due to the flexibility of the employed polymer material concept.

We developed a simple two-step replication method to transfer arrays of high aspect ratio nanopillars into films of poly(L-D,L-lactic acid) (PLLA). Such structures are promising model surfaces for tissue engineering applications. From arrays of 1 mu m high and 200 nm wide pillars produced with e-beam lithography and reactive ion etching negative replicas were first formed by polydimethylsiloxane (PDMS) casting. The final replicates were produced by solvent casting from 1% to 4% solutions of PLLA in chlorinated solvents on the PDMS templates. The silicon masters provide excellent stability and reusability, whereas the flexibility and low surface energy of the PDMS are necessary for the separation of the casts made with PLLA, a brittle material which is difficult to handle. AFM and SEM characterizations confirmed a high fidelity reproduction of the structures with aspect ratios of 1:5. In vitro tests using mouse neural stem cells seeded on nanopillars showed that the cells sense the nano-sized topography and respond accordingly by orienting themselves. (C) 2010 Elsevier B.V. All rights reserved.

A novel process route is presented for the fabrication of three-dimensional (3D) patterns with both vertical and inclined profiles in close vicinity on the same substrate. The 3D patterns were generated by dose-modulated electron-beam lithography (EBL) in polymeric resist combined with a thermal annealing (reflow) post-treatment at a moderate temperature. Thus, technical limitations usually connected with grayscale EBL to manufacture continuous patterns were overcome. 3D sawtooth structures which exhibit both sharp and continuous profiles were generated and slopes up to 27^o with smooth surfaces were achieved.

Nanoimprinted resist pre-forms were modified using thermal reflow. This post-processing of binary structures enabled us to generate lens-like 3-D structures with different shapes by time- and surface chemistry controlled spreading. The method was extended to feature dimensions down to 100nm. Surfactant coated line nanostructures were found to be limited by a maximum aspect ratio for imprinted pre-forms. This powerful post-processing method can be used either directly as post-processing step in production or for the fabrication of 3-D stamp copies with the desired shapes.

Here we describe the use of a backside exposure method for the creation of high aspect ratio tapered microstructures with nano-porous sidewalls. These sidewalls result from the exposure and curing conditions of the SU8 matrix. The structures show ultra-hydrophobic behavior with water contact angles of more than 160°, without an additional coating of the SU8 polymer. By choosing appropriate exposure conditions, needlelike structures can be created with a high level of porosity, covering their entire surface. The contact angle hysteresis values of such structures lie in the range of 20°. After an additional deposition of smooth and thin metallic gold film and coating it with an alkyl thiol selfassembled monolayer (SAM), we were able to decrease this hysteresis to values of around 10°. By using thin and rough metallic films like wet chemically oxidized titanium oxide and a fluoralkylsilane SAM, the hysteresis values could be reduced to only 4°.

In this paper we report on the optical gas sensitivity of a sputtered multilayer system consisting of InxOyNz thin films and gold-nano-clusters. This system shows a reversible change in the optical absorption (increase or decrease of absorbance) during exposure to reducing or oxidizing gases in air. The gold-nano-clusters are randomly distributed on and inside the multilayer system. Here, we demonstrate the optical gas sensitivity at a temperature of 400 °C and three exemplary gas samples: carbon monoxide in dry synthetic air, nitrogen dioxide in dry synthetic air and hydrogen in dry synthetic air. We show that the incorporation of the gold-clusters leads to a broad absorption peak in the range of visible light due to the excitation of localized surface plasmons. The corresponding resonance wavelength is shifted by gas exposure that in turn changes the optical behavior of the multilayer system.

Plano-convex microlens arrays of organic-inorganic polymers with tailored optical properties are presented. The fine-tuning of each microlens within an array is achieved by confining inkjet printed drops of the polymeric ink onto pre-patterned substrates. The lens optical properties are thus freely specified, and high numerical apertures from 0.45 to 0.9 and focal lengths between 10 μm and 100 μm are demonstrated, confirming theoretical predictions. Combining nanoimprint lithography approaches and inkjet printing enables using the same material for the microlenses and their substrates, improving the optical performances. Microlens arrays with desired specifications are printed reaching yields up to 100% and high lens reproducibility with standard deviations of the apparent contact angle under 1° and of the numerical apertures and focal lengths under 6%. Microlens arrays involving lenses with different characteristics, e.g. multi focal length, and thus focal planes separated by only few microns are printed with the same reproducibility.

Hybrid polymers have been already widely applied in photonic applications to manufacture microlenses or 2D and 3D waveguides. Thus, they are promising candidates to manufacture optical systems down to the chip level. A brief review on hybrid polymers consisting of both inorganic and organic functional units and thus combine superior material properties in just one material class will be given in this report. The material properties, which can be adjusted to the application in wide ranges enable to fabricate micro-optical elements (e.g. microlenses) using replication techniques such as UV-assisted replication or nano-imprint lithography. Aside of their applicability in 2D, emphasis will be in particular on the evaluation of hybrid polymer materials for two-photon absorption lithography, which is employed to directly manufacture sophisticated 3D photonic structures impossible to be generated with conventional 2D techniques.

In this paper we present new results achieved with a sputtered multilayer system consisting of In"xO"yN"z and gold-nano-dots. This system shows not only electrical but also optical gas sensitivity. The optical sensing effect is enhanced by the gold-nano-dots which are randomly distributed on and inside each In"xO"yN"z layer. The optical measuring system consists of a tuneable light source (or alternatively of a simple light emitting diode) and a CdS-photoresistor. As an example of the optical gas sensing effect we show the sensitivity to hydrogen at a temperature of 400^oC.

The high throughput and large area nanostructuring of flexible substrates by continuous roller processes has great potential for future custom applications like wire grid polarizers, antireflection films, or super-hydrophobic surfaces. For each application different material characteristics have to be considered, e.g. refractive index, hydrophobicity, or dry etch stability. Herein, we show experimental results of nanoimprint lithography resist developments focused on inkjetable and photo-curable resists suitable for high throughput production, especially roll-to-roll NIL. The inkjet deposition of the novel materials is demonstrated by the use of different state-of-the-art inkjet printheads at room temperature. A plate-to-plate process on silicon substrates was successfully implemented on a NPS300 nano patterning stepper with previously inkjet dispensed NIL resist. Furthermore, we demonstrate a throughput of 30 m min-1 in a roller NIL process on PET. Dry etching of unstructured thin films on Si wafers was performed, and it was demonstrated that the etch stability in Si is tunable to a value of 3.5:1 by a concise selection of the resist components. The surface roughness of the etched films was measured to be < 2 nm, after etching of around 100 nm of the resist films what is an essential factor for a low line edge roughness. All resists reported herein can be deposited via inkjet dispensing at room temperature, are suitable for continuous high throughput imprinting on flexible substrates, and are applicable in step-wise NIL processes with good etch resistance in dry etch processes.

Advanced micro- and nanofabrication processes are constantly evolving from academic R&D environment towards real production technology. Therefore, the availability of suitable polymers for optical applications plays a crucial role to satisfy not only application based requirements but also the compatibility to industrial production technologies. In this context, UV-curable hybrid polymers, i.e. inorganic-organic materials obtained by sol-gel chemistry, were recently implemented into mass production environment, e.g. for micro-lenses in mobile device applications. In this contribution, we report on the development of innovative hybrid polymers and their tailoring towards an easy and fast processing with reliable and reproducible performance output for industrial large-scale production. Based on a discussion on standard process parameters with respect to optimize the material’s performance, the technical demands of industrial manufacture to the hybrid polymers will be subsequently reviewed by giving selective examples. This will be complemented by a brief description of current R&D activities adapting hybrid polymers to future patterning technologies.

The last 40 years have impressively shown that adding additional dimensionality makes an important difference in cell culture microenvironments. With this in mind, a variety of 3D microfluidic cell culture platforms have previously been fabricated using a broad spectrum of materials. One prominent example is the “3D-KITChip”, a polymer chip for 3D cell culture in form of an array of microcontainers provided with porous bottoms or walls to allow an active perfusion of the cells therein with cell culture medium within dedicated microfluidic bioreactors. In this chapter, the fabrication of the KITChip by different means of polymer micromolding is described as well as different methods to introduce porosity in the chips. Furthermore, various techniques to tailor the biophysicochemical microenvironment of the cells cultured in the containers of the KITChip are discussed. The end of the chapter deals with the integration of the chip into the bioreactors.

Microlens and prism arrays were fabricated using multi-level electron beam patterning combined with thermal reflow. The molecular weight dependent processing allows selective transfer of stepped into sloped resist structures with smooth surfaces.

A step-and-repeat nanoimprint lithography (SR-NIL) process on a pre-spin-coated film is employed for the fabrication of an integrated optical device for on-chip spectroscopy. The complex device geometry has a footprint of about 3 cm2 and comprises several integrated optical components with different pattern size and density. Here, a new resist formulation for SR-NIL was tested for the first time and proved effective at dramatically reducing the occurrence of systematic defects due to film dewetting, trapped bubbles, and resist peel-off. A batch of 180 dies were imprinted, and statistics on the imprint success rate is discussed. Devices were optically characterized and benchmarked to an identical chip that was fabricated by electron-beam lithography. The overall performance of the imprinted nanospectrometers is well-aligned with that of the reference chip, which demonstrates the great potential of our SR-NIL for the low-cost manufacturing of integrated optical devices.

We present a new platform for the optical analysis of biomolecules based upon the polysaccharide chitosan. The versatile, stable, and compatible nature of chitosan makes it an ideal material for integrating biological materials in microfabricated systems. Chitosan’s pH-responsive solubility allows electrochemical deposition, while its chemical reactivity enables facile coupling of proteins, oligonucleotides, and other biomolecules by covalent bonds. This work demonstrates the spatially selective assembly of a fluorescent molecule on chitosan and its applicability to microscale optical transducers. We define multimode waveguides and fluidic channels on a Pyrex wafer using a single layer of SU-8. Our implementation of sidewall patterning of transparent electrodes (indium tin oxide) on SU-8 structures is demonstrated and can be highly beneficial to fluorescent signal transduction. In this optical configuration, normally incident excitation light illuminates a chitosan surface on the vertical face of a collector waveguide intersected by a microfluidic channel. We demonstrate the collection of the optical signal in the integrated waveguide and analyze the signal by coupling the waveguide to a grating spectrometer.

An intensive, energy-based analysis of the thermal reflow of thermoplastic polymer structures is presented. Poly (methyl methacrylate) (PMMA) was patterned by grayscale electron beam lithography. The obtained rectangular, micron-scale structures were transformed into lens-like structures by thermal reflow near the glass transition temperature of the original PMMA. Representative parameters obtained from these reflow experiments were used to model the reflow process by using a new, energy-based, finite element, soapfilm method using the free software Surface Evolver. The time-, temperature- and molecular-weight-dependent geometry evolution of the PMMA structures could be described by an apparent contact-angle-evolution time constant and a shape-evolution time constant. The developed model allows the prediction of intermediate geometries during the reflow process occurring between the initial and the final energy optimal geometry. The proposed model is independent from the explicit knowledge of material-specific parameters such as viscosity or glass transition temperature. Extensive experimental data for PMMA reflow is provided. Simulation examples are given for a contact-angle-dominated reflow which demonstrate a good agreement between model and experiment.

Nanoimprint stamp cavities with vertical and sloped sidewalls show different filling behaviors during thermal nanoimprinting resulting from the varying ability of the viscous polymer to wet the surface during the thermal imprint step. In this paper, the authors describe the formation of prefill states already in the pressure-less contact phase, before squeeze flow begins to fill the cavities. These stable states are created by a constant contact angle formed at the sidewall, and the states themselves generate surface topographies in the resist below the imprint cavities which are dependent upon the surface energy, the geometry of the stamp cavities, and the resist thickness. Therefore, prefilling topographies, formed once a stamp is in contact with a liquid polymer surface and resulting in a transformation of the resist layer with homogeneous thickness into a thickness modulated film, have to be considered as the standard case in molding. Furthermore, due to the local balance of material pinning and wetting mechanisms, cavities preferentially fill from the sloped sidewall and, therefore, this observed phenomenon is highly relevant for the defect-free replication of 3-D surface topographies.Nanoimprint stamp cavities with vertical and sloped sidewalls show different filling behaviors during thermal nanoimprinting resulting from the varying ability of the viscous polymer to wet the surface during the thermal imprint step. In this paper, the authors describe the formation of prefill states already in the pressure-less contact phase, before squeeze flow begins to fill the cavities. These stable states are created by a constant contact angle formed at the sidewall, and the states themselves generate surface topographies in the resist below the imprint cavities which are dependent upon the surface energy, the geometry of the stamp cavities, and the resist thickness. Therefore, prefilling topographies, formed once a stamp is in contact with a liquid polymer surface and resulting in a transformation of the resist layer with homogeneous thickness into a thickness modulated film, have to be considered as the standard case in molding. Furthermore, due to the local balance of material pinning and wetti...

Sloped and stepped 3D structures were added to surface-patterned resists using grey-scale electron beam lithography and thermal reflow. A poly(methyl methacrylate) resist with moderate initial molecular weight of 120 kg/mol was chosen, which enabled processing with both nanoimprint and electron beam lithography. Using proper exposure doses, a molecular weight distribution was generated that allowed a selective thermal postprocessing of the exposed steps while the imprinted gratings on top of the resist were preserved. This allows fabricating mixed structures of microprisms surrounded by large-area nanogratings in the same resist layer. Working stamps were casted from the template pattern and subsequently replicated using thermal nanoimprint. As a possible application, backlight devices with arrays of light outcoupling prisms can be seen.

Novel 3D resist structures are generated with both smooth slopes and stepped resist profiles on the same substrate and in very close vicinity. By performing gray-scale electron-beam exposure and development steps twice with different dose ranges, a selective transformation of multilevel structures into continuous slopes upon thermal treatment was enabled. The molecular weight dependence was analyzed and related to the locally different ability of the resist to flow, which enables one to selectively address resist structures which should be altered while others stay unaffected. The technique has large potential for prototyping elements and devices and can be used to fabricate stamps with complex 3D surface patterns for fabrication using nanoimprint.

A manufacturing concept to fabricate working stamps with defined mesa structures using combined nanoimprint and photolithography is presented. OrmoStamp, an UV-curable organic-inorganic hybrid polymer, was used as mold material. 30 μm high large mesa structures (4×4 mm2) with sharp borders and almost vertical sidewalls were manufactured. On top they featured nanograting patterns with 200 nm height and lateral size as a surface relief. The good thermal decoupling of stamp body and imprinted substrate and the high planarity (divergence

3D electron beam lithography and thermal reflow were combined to fabricate structures with multilevel and continuous profiles. New shapes, smooth surfaces and sharp corners were achieved. By using exposure with variable doses, up to 20 steps were fabricated in a 500 nm thick resist with a lateral resolution of 200 nm. Steps were reflowed into continuous slopes by thermal post-processing, and were transferred into silicon substrates by proportional plasma etching. The method can be used for the fabrication of 3D nanoimprint stamps with both sharp features and continuous profiles.

Hybrid transparent working stamps with both a surface relief and absorbing mask pattern were fabricated by replicating nanostructures in an Ormostamp film on prepatterned glass substrates. By using a combined nanoimprint and photolithography process, self-aligned mixed patterns of nano- and microstructures can be generated within one single resist layer. In this article the authors present a simple process based on the organic-inorganic hybrid polymer Ormostamp by replication on prepatterned Borofloat substrates. Using these working stamps, grating arrays with 35 nm half pitch were replicated in thermoplastic UV-curable resist. The method is easy to employ for generating mesas with nanostructures on top or the backfilling with microstructures in thermal nanoimprint lithography applications.

We report a new approach for microfluidic optical bioanalysis that is based on the electrically driven assembly of bio-components on a transparent sidewall and the optical detection of the assembled components using planar waveguides. This allows localized electrical signals for bio-assembly and optical signals for bio-detection that can easily be applied in MEMS systems. We demonstrate a BioMEMS design incorporating this scheme and its output signal when using fluorescent detection.

The replicated sol-gel stamps used in this work were fabricated according to a process developed. As a substrate, thin Ni foils (250 ìm thickness) were used. The pattern was imprinted from an intermediate polycarbonate replica into an approx. 40 ìm thick Ormostamp® layer by UV-NIL. The metal shims were cut, wrapped around a 66 mm diameter metal cylinder and mechanically attached to the home-build roll-to-roll (R2R) embossing setup at VTT.

In this work, we used a poly(methyl methacrylate) (PMMA) substrate which was at first pre-patterned with a nanoscale binary line grating by thermal NIL. A rather thick polymer slab (3 mm) ensured a sufficient mechanical stability when the substrate is exposed to the heat load of a second thermal imprint step. The linear grating was replicated onto the PMMA slab at 165 °C. A reduced pressure of 0.25 MPa enabled the generation of a surface patterning without reducing the slab thickness, which was previously observed for increased temperatures and imprint pressure. The second imprint was added into the linear surface-gratings by thermal imprinting using a nickel stamp with micron scale blaze gratings. The rotation controlled patterning was realized by Step and Stamp Imprint Lithography (SSIL) using NPS300 nanoimprinting stepper with rotation imprint head. The rotating head introduces ability to control X/Y positioning and angular orientation of the stamp. The imprinting head can be rotated between -90° and +90° with accuracy of 0.1°