Cyclic olefin polymers (COPs) are increasingly popular as substrate material for microfluidics. This is due to their promising properties, such as high chemical resistance, low water absorption, good optical transparency in the near UV range and ease of fabrication. COPs are commercially available from a range of manufacturers under various brand names (Apel, Arton, Topas, Zeonex and Zeonor). Some of these (Apel and Topas) are made from more than one kind of monomer and therefore also known as cyclic olefin copolymers (COCs). In order to structure these materials, a wide array of fabrication methods is available. Laser ablation and micromilling are direct structuring methods suitable for fast prototyping, whilst injection moulding, hot embossing and nanoimprint lithography are replication methods more appropriate for low-cost production. Using these fabrication methods, a multitude of chemical analysis techniques have already been implemented. These include microchip electrophoresis (MCE), chromatography, solid phase extraction (SPE), isoelectric focusing (IEF) and mass spectrometry (MS). Still much additional work is needed to characterise and utilise the full potential of COP materials. This is especially true within optofluidics, where COPs are still rarely used, despite their excellent optical properties. This review presents a detailed description of the properties of COPs, the available fabrication methods and several selected applications described in the literature.

Cyclic olefin polymers : Emerging materials for lab-on-a-chip applications

In this paper, a new mold-transfer method to pattern piezoelectric polymer has been developed and applied to fabricate innovative dome and bump shape polyvinylidene-fluoride-trifluoroethylene (PVDF-TrFE) films. The dome and bump shape PVDF-TrFE films have been successfully fabricated and characterized as a sensing component for flexible tactile sensors. The tactile sensors developed using these polymer microstructures show a high sensitivity which can measure as small as 40 mN force for bump shape sensors and 25 mN for dome shape sensors. The newly developed fabrication method provides a flexible way to pattern the piezoelectric polymer with different shapes and dimensions, including bump and dome shape piezoelectric polymer microstructures. In addition, a selective dc poling method for the PVDF-TrFE film has been developed for fabricating precisely located piezoelectric sensors with minimum crosstalk. The bump and dome shape PVDF-TrFE films developed in this paper can have numerous applications for microcatheters or other minimally invasive biomedical devices.

Flexible Dome and Bump Shape Piezoelectric Tactile Sensors Using PVDF-TrFE Copolymer

Disclosed is a method of fabricating a molded structure including both micro lenses and metallic pins. The method comprises the steps of providing a mold apparatus having a set of first cavities and a set of second cavities, depositing a first material in the first cavities to form a set of metallic pins, and depositing a second material in the second cavities to form a set of micro lenses. The formed molded structure comprises a substrate, a set of molded microlenses on said substrate, and a set of molded metallic pins on that same substrate. The metallic pins may be formed as alignment pins or as electrical connectors. The invention enables the micro lenses and metallic pins to be manufactured by way of molding on a common substrate for the first time.

Hybrid optical/electronic structures fabricated by a common molding process

We describe a new method for etching patterns in silver, copper, or gold, or other plate metal thin films. A pattern of a hard mask is placed onto the surface of the thin film, followed by a step of reactive ion etching using a plasma formed using a gas feed of some combination of some amounts of methane (CH 4 ) and hydrogen (H 2 ), and some or no amount of Argon (Ar). The areas of silver, copper or gold not covered by the hard mask are etched while the hard mask protects those areas that will form the raised portions of thin film in the final structure.

Patterning thin metal films by dry reactive ion etching

A device couples energy from an electromagnetic wave to charged particles in a beam. The device includes a micro-resonant structure and a cathode for providing electrons along a path. The micro-resonant structure, on receiving the electromagnetic wave, generates a varying field in a space including a portion of the path. Electrons are deflected or angularly modulated to a second path.

Structures and methods for coupling energy from an electromagnetic wave

Various techniques for the fabrication of highly accurate master molds with precisely defined microstructures for use in plastic replication using injection molding, hot embossing, or casting techniques are disclosed herein. Three different fabrication processes used for master mold fabrication are disclosed wherein one of the processes is a combination of the other two processes. In an embodiment of the first process, a two-step electroplating approach is used wherein one of the metals forms the microstructures and the second metal is used as a sacrificial support layer. Following electroplating, the exact height of the microstructures is defined using a chemical mechanical polishing process. In an embodiment of the second process, a modified electroforming process is used for master mold fabrication. The specific modifications include the use of Nickel-Iron (80:20) as a structural component of the master mold, and the use of a higher saccharin concentration in the electroplating bath to reduce tensile stress during plating and electroforming on the top as well as sides of the dummy substrate to prevent peel off of the electroform. The electroforming process is also well suited towards the fabrication of microstructures with non-rectangular cross sectional profiles. Also disclosed is an embodiment of a simple fabrication process using direct deposition of a curable liquid molding material combined with the electroforming process. Finally, an embodiment of a third fabrication process combines the meritorious features of the first two approaches and is used to fabricate a master mold using a combination of the two-step electroplating plus chemical mechanical polishing approach and the electroforming approach to fabricate highly accurate master molds with precisely defined microstructures. The microstructures are an integral part of the master mold and hence the master mold is more robust and well suited for high volume production of plastic MEMS devices through replication techniques such as injection molding.

Microfabricated structures and processes for manufacturing same

A novel fabrication scheme to develop high-throughput plastic microlenses using injection-molding techniques is realized. The initial microlens mold is fabricated using the well-known reflow technique. The reflow process is optimized to obtain reliable and repeatable microlens patterns. The master mold insert for the injection-molding process is fabricated using metal electroforming. The electroplating process is optimized for obtaining a low stress electroform. Two new plastic materials, cyclo olefin copolymer (COC) and Poly IR 2 are introduced in this work for fabricating microlenses. The plastic microlenses have been characterized for their focal lengths that range from 200 µm to 1.9 mm. This technique enables high-volume production of plastic microlenses with cycle times for a single chip being of the order of 60 s.

Sreeram Appasamy

Papers

Microfabricated structures and processes for manufacturing same

High-throughput plastic microlenses fabricated using microinjection molding techniques

Development of high throughput plastic microlenses using a replaceable injection mold disk