Chris Steinert

Rapid prototyping of microfluidic chips in COC

We present a novel, cost-efficient process chain for fast tooling and small-lot replication of high-quality, multi-scale microfluidic polymer chips within less than 5 days. The fabrication chain starts with a primary master which is made by well-established cleanroom processes such as DRIE or negative SU-8 resist based surface micromachining. The formation of undercuts in the master which would complicate demolding is carefully avoided. Secondary PDMS masters or epoxy-based masters which are more suitable for common polymer replication schemes such as soft-embossing, hot-embossing or injection molding are subsequently cast from the primary masters. The polymer replica are mainly made of COC and show excellent fidelity with the conventionally micromachined master while displaying no degeneration, even after more than 200 cycles. The use of other polymers such as PMMA is also possible. The process chain further includes surface modification techniques for overall, long-term stable hydrophilic coatings and for local hydrophobic patches as well as a durable sealing based on thermal bonding.

A tuneable and highly-parallel picolitre-dispenser based on direct liquid displacement

We present a new method for the highly parallel and simultaneous delivery of a multitude of reagents in the picoliter range. This method is based on direct displacement of the liquids using an elastomer stamp which simultaneously actuates up to 96 different dosing channels, at a pitch of 500 /spl mu/m. We were able to tune droplet volume from 150-720 pl and droplet speed from 0,2m/s-2,8m/s using printheads with 50 /spl mu/m nozzles. In contrast to all other inkjet techniques the new direct displacement method enables the precise control of dispensing quantity in the picoliter range regardless of reagent viscosity.

An improved 24 channel picoliter dispenser based on direct liquid displacement

For the first time we present a systematic study concerning the relation between nozzle diameter and ejected droplet volume of a highly parallel picoliter dispenser. Such dispensers are essential parts for the mass fabrication of microarrays and are able to dispense up to 96 different reagents at a pitch of 500 /spl mu/m simultaneously. In contrast to an earlier design we investigated different nozzle diameters. The change from 35 /spl mu/m to 60 /spl mu/m in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum of dispensed volumes have been determined to be 125 pl and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the CV of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).

A tunable and highly-parallel picoliter-dispenser based on direct liquid displacement

We present a new method for the highly parallel and simultaneous delivery of a multitude of reagents in the picoliter range. This method is based on direct displacement of the liquids using an elastomer stamp which simultaneously actuates up to 96 different dosing channels, at a pitch of 500 /spl mu/m. We were able to tune droplet volume from 150-720 pl and droplet speed from 0,2m/s-2,8m/s using printheads with 50 /spl mu/m nozzles. In contrast to all other inkjet techniques the new direct displacement method enables the precise control of dispensing quantity in the picoliter range regardless of reagent viscosity.

Microfluidics and Beyond – Devices for Applications in Biotechnology -

For the performance of certain analytical and diagnostic tasks in modern Life Science applications high throughput screening (HTS) methods are essential. Miniaturization, parallelization and automation allow to decrease consumption of expensive materials and lead to faster analyzing times. The miniaturization of total assay volumes by the use of microtiter plates as well as the microarray technology have revolutionized the field of biotechnology and Life Sciences. Neither printing of microarrays with droplet volumes of several picoliters, nor handling of precious enzymes in the upper nanoliter range can be accomplished with traditional liquid handling devices like air displacement pipettes. The development of novel low volume liquid handling devices, which are subject to current research, addresses the diverse requirements shifting steadily to lower volumes. Various novel non-contact dispensing methods in the nanoliter and picoliter range are presented and classified according to their working principles like air displacement and direct displacement methods (TopSpot ® , NanoJet TM , Dispensing Well Plate TM ). Properties of the various methods are compared in terms of flexibility, integration density, speed of operation, precision, addressable volume range and amenability to multi-parallel operation. By integrating processing steps of biological assays within these novel non-contact dispensing devices multifunctional Lab-on-a-chip (LOAC) devices can be developed. A prototype of such a flexible and modular application platform was developed. This platform enables to perform various processing steps (e.g. PCR, post-processing) in one chip with subsequent probe transfer into another chip with a different functionality (e.g. detection). This basically points into the direction to reach new functionalities by combining advantages of novel low volume liquid handling devices with LOAC functionality.