Mike Stubenrauch

Liquid‐Crystalline Elastomer Microvalve for Microfluidics

Dr. A. Sanchez-Ferrer Food & Soft Materials Science Group Institute of Food, Nutrition & Health ETH Zurich, Schmelzbergstrasse 9, 8092 Zurich, Switzerland E-mail: antoni.sanchez@agrl.ethz.ch Dr. A. Sanchez-Ferrer , Prof. H. Finkelmann Albert Ludwigs University Institute for Macromolecular Chemistry Stefan-Meier-Str. 31, 79104 Freiburg, Germany Fischl , Dr. . T Dr. M. Stubenrauch , Dr. A. Albrecht , Prof. H. Wurmus , Prof. M. Hoffmann Ilmenau University of Technology Faculty of Mechanical Engineering Department of Micromechanical Systems Max-Planck-Ring 14, 98693 Ilmenau, Germany

Black silicon—new functionalities in microsystems

Black silicon and its application as a new assembly method for silicon wafers at room temperature is presented. Needle-like structures on the surface after deep reactive ion etching with a length of 15–25 µm and 300–500 nm in diameter interlock with each other to form a bonding interface. After compression of two wafers at room temperature they generate retention forces up to 380 N cm−2 (3.8 MPa). If low contact forces are applied with partially interlocking of the needles, it is possible to generate a reversible Velcro®-like assembly. This new bonding process can be used for applications in the area of microfluidics with catalysts, microoptical or mechanical mountings or carrier wafer bonding in microelectronics.

Silicon on Ceramics―A New Integration Concept for Silicon Devices to LTCC

A new integration concept for MEMS-devices to ceramic substrates based on a new bonding technique between nano-scaled black silicon (BSi) and an adapted LTCC substrate is presented. The novel technique allows combining advantages of silicon and ceramic technology whereby a new wafer compound material (silicon on ceramics) and innovative ceramic carrier as well as chip packages become available. The new compound is fabricated by the use of standard technologies (reactive ion etching, lamination, and pressure assisted sintering) without additional materials and devices. A bonding strength up to 1750 N/cm2 and gas tightness are remarkable features of the bond interface. Simultaneously, electrical interconnects between silicon and LTCC can be manufactured during lamination and sintering.

Suspended nanowire web

A complex three-dimensional, nanowire based nanoarchitecture is presented, which can be processed by high-throughput bottom-up procedures without any high-resolution lithography. It combines the benefits of three self-organization mechanisms to produce nanostructures, i.e., the formation of nanoneedles, the droplet formation out of a thin metal film, and the vapor-liquid-solid growth of nanowires. The principle is demonstrated for a silicon based suspended nanowire web. Cell adherence on this assembly was found to be superior to other nanostructures. The possibility of fluid transport beneath the nanowire web enables improved microcatalyst principles and the realization of novel interfaces for biosensing or bioelectronics.

Integration of 3-D cell cultures in fluidic microsystems for biological screenings

A life support system for the cultivation of adherent 2‐D and scaffold‐based 3‐D cell cultures in a microfluidic device, a Bio‐Micro‐Electro‐Mechanical System (BioMEMS) is presented. The miniaturization level and system set‐up allow incubator‐independent operation modes and long‐term experiments with real‐time microscope observation. A dedicated seeding procedure for adherent cells into the microstructures is one key issue of the BioMEMS developed. Several seeding methods for the cells were evaluated. Biocompatibility of all materials, surfaces and methods could be demonstrated. First experiments with several cell types show the feasibility of the approach employing standard laboratory protocols. At present, the modular design and set‐up offer a broad application spectrum as well as its future extension to e.g. cultivation of other cell types, coupled cultivation chambers and the implementation of other manipulation or analysis components.

Mechanical Properties and Residual Stress of Thin 3C-SiC(100) Films Determined Using MEMS Structures

3C-SiC(100) was grown on Si (100) in a thickness range between 40 and 500 nm by low pressure chemical vapor deposition. The mechanical properties and the residual stress were determined using the length dependence of the resonance frequencies of cantilevers and beams. Taking into account the influence of the cantilever bending and the stress gradients the Young’s modulus of the 3C-SiC(100) was obtained. It decreases with decreasing thickness of the epitaxial layer grown on Si (100).

Residual stress measurements and mechanical properties of AlN thin films as ultra-sensitive materials for nanoelectromechanical systems

Knowledge of the mechanical properties of new materials is essential for their usability and functionality when used in micro- and nanoelectromechanical systems (MEMS/NEMS). Recently, Group III nitrides have gained interest for MEMS and NEMS application. In order to test these materials, three different types of microstructures were fabricated by etching processes: rhombus-shaped structures and doubly-clamped beams for the determination of tensile and compressive stress as well as cantilever structures for the determination of stress gradients in the surface. Furthermore, three different methods were applied for determining the residual stress of AlN thin films: wafer bending measurements, Fourier transform infrared spectroscopic ellipsometry before the etching processes and laser Doppler vibrometer measurements after the etching processes using the doubly-clamped beams. All three methods showed a good correlation of the residual stress in the AlN thin films.

Automated control of micromanipulators - A tool for BioMEMS based cell culture

The progress in regenerative medicine in combination with the trend towards miniaturization leads to an increased usage of bio-microsystems for cell culturing. Similar processes can be found in the field of biomaterial research. New scaffold materials and scaffold fabrication technologies give a possibility to create biocompatible biodegradable 3-dimensional artificial extra cellular matrices to improve implant materials designed by tissue engineering. For small and delicate technical and biological structures (hydrogels for scaffolds, cells) a high resolution and precise manipulation system is needed. A semi-open BioMEMS structure offers access to cultivated cells and to the scaffold structures. The bio-microsystem consists of a structured silicon substrate bonded to a glass cover with orifices. Polymer tube adapters, directly bonded to the silicon via nanostructured surfaces, connect it to a perfusion system for the long term cultivation of mammalian or human chondrocytes or fibroblasts. Externally fabricated scaffolds are integrated into the cultivation chambers. In this paper we present a piezo driven micromanipulator with automated control. Several tools such as grippers and needles can be fixed on the manipulators. The manipulation unit is completed by an observation unit to monitor the processes. Image processing software provides parameters for the control algorithm by detecting the position of the manipulation devices. So, a positioning of the tools is achieved in 2D inside the cultivation chamber of the microsystem. It is possible to influence technical and biological structures by deliberate mechanical manipulation.

Microsystems for the Characterization of 3D-ECM Analogous Bio-Interfaces

Characteristics of scaffold materials for tissue engineering have to be adapted to the respective cell lines. Especially cartilage cells require an artificial 3-dimensional extra cellular matrix, to behave and grow like in natural environment. To reach this goal, biomaterials have to be developed that fulfill these requirements. A novel structuring technique for degradable polymer scaffolds is 2-photonpolymerization. For defining best chemical and geometrical properties a microsystem is necessary that can be used as a test-environment in cell-cultivation-experiments. In this paper we describe both materials for and the process of 2-photonpolymerization. We introduce a silicon-glass-micro system with scaffold integration option for testing of scaffold materials and structures.

Bio-Microsystem for Cell Cultivation and Manipulation and its Peripherals

The smart combination of silicon, glass and polymers offers microenvironments with properties applicable to cultivation, observation and manipulation of cells. Function modules of the system and a concept for their use in the laboratory as well as the combination with adapted peripheral devices form such platforms for cell and biocompatibility analyses and cell breeding. Requirements for the design of these modular microsystems and its auxiliary components determine the main components of the cultivation and manipulation system which are introduced in this paper.