Klaus Plewa

Liquid Glass: A Facile Soft Replication Method for Structuring Glass

Liquid glass is a photocurable amorphous silica nanocomposite that can be structured using soft replication molds and turned into glass via thermal debinding and sintering. Simple polymer bonding techniques allow the fabrication of complex microsystems in glass like microfluidic chips. Liquid glass is a step toward prototyping of glass microstructures at low cost without requiring cleanroom facilities or hazardous chemicals.

Sensitivity optimization of injection-molded photonic crystal slabs for biosensing applications

For label-free assays employing photonic crystal slabs (PCSs), the sensitivity is one of the most important properties influencing the detection limit. We investigate the bulk sensitivity and the surface sensitivity of 24 different PCSs fabricated by injection molding of PMMA and subsequent sputtering of a Ta2O5 high-index layer. The duty cycle of the linear grating is varied in steps of 0.1 between 0.2 and 0.7. Four different Ta2O5 layer thicknesses (89 nm, 99 nm, 189 nm, 301 nm) are deposited. Both bulk and surface sensitivity are optimal for a Ta2O5 layer thickness of 99 nm. The maximum bulk sensitivity of 138 nm/RIU is achieved for a duty cycle of 0.7, while the maximum surface sensitivity of 47 nm/RIU is obtained for a duty cycle of 0.5. Good agreement between experimental results and finite-difference time-domain (FDTD) simulations is observed. The PCSs sensitivity is linked to the mode intensity distribution.

Micro PIM moves into the zone of industrial possibility

Increasing demand for ever-smaller devices presents challenges for materials science. German researchers are looking at the possibilities of micro powder injection moulding, and how to match the process to the needs of large-scale industrial production…

Manufacturing of High-Grade Micro Components by Powder Injection Molding

Powder injection molding (MicroPIM) has a considerable potential for the production of high-value metal and ceramic micro components. This does not only apply to technical aspects but, due to the deployability of mass production, also to economic ones. The current status can be summed up by the following key data: latest trials revealed smallest struc-tural details in the 10µm range or lower. Theoretical densities of up to 99% were achieved depend-ing on the particular powder applied. Typical materials processed are metals (Fe, Cu, 316L, 17-4PH, W and W-alloys etc.) or ceramics (aluminum/zirconium oxide etc.). Best surface qualities were obtained with ultrafine or even nano-doped ceramic powders. Another major line of development is multi-component or assembly injection molding. These proc-esses do not only reduce assembly expenditure, but also allow for the use of new functional material combinations. Interesting examples are ceramic micro heating elements or gear wheel/shaft samples which can be performed as fixed or movable combinations. Micro inmold-labelling using PIM feed-stocks offers further promising opportunities.

Towards Reliable Organs-on-Chips and Humans-on-Chips

The artificial production of complete three-dimensional vascularized functional organs is still a research challenge, although recent advances are opening up new horizons to the treatment of many diseases by combining synthetic and biological materials to produce portions of veins, capillaries, arteries, skin patches and parts of bones and soft organs. Counting with artificially obtained completely functional replicas of human organs will constitute a benchmark for disease management, but there is still a long way to achieve the desired results and produce complete organs in vitro. In the meantime, having at hand simple biomimetic microsystems capable of mimicking the behaviour of complete complex organs, or at least of some of their significant functionalities, constitutes a realistic and very adequate alternative for disease modeling and management, capable of providing even better results than the use of animal models. These simplified replicas of human organ functionalities are being developed in the form of advanced labs-on-chips generically referred to as “organs-on-chips” and are already providing interesting results. This chapter provides an introduction to this emerging area of study and details different examples of organs-on-chips and their development process with the aid of computer-aided design and engineering technologies and with the support of rapid prototyping and rapid tooling resources.

Rapid prototyping of glass microfluidic chips

In academia the rapid and flexible creation of microfluidic chips is of great importance for microfluidic research. Besides polymers glass is a very important material especially when high chemical and temperature resistance are required. However, glass structuring is a very hazardous process which is not accessible to most members of the microfluidic community. We therefore sought a new method for the rapid and simple creation of transparent microfluidic glass chips by structuring and sintering amorphous silica suspensions. The whole process from a digital mask layout to a microstructured glass sheet can be done within two days. In this paper we show the applicability of this process to fabricate capillary driven microfluidic systems.

Powder injection moulding of multi-material devices

An important goal in research and development (R+D) is to enhance powder injection moulding (PIM) to combine two or more materials with different properties in a single piece manufactured in one process cycle. A further advantage is the considerable reduction of mounting costs. In principle, a certain range of options should be suitable for creating multi-component products. An important option is two-component PIM which is mainly characterized by a sophisticated sintering procedure taking into account the kinetics of all powder types involved. Investigations into how to fabricate immobile or mobile ceramic shaft-wheel components have been carried out successfully and even metal and ceramic materials can be connected for fixed joints. A further opportunity is opened up by In-mould Labelling PIM which uses powder filled tapes as the first component. Here again particular attention has to be paid to the sintering procedure, but if this is done, samples containing nano-sized powders in the surface area of the whole body can be obtained.

Micro systems need a boost in manufacturing methodologies

While macroscopic powder injection moulding is drawing the attention of mass manufacturing and winning plaudits for its high process and economic efficiency, its micro variant still faces challenges…