Microflow extraction: A review of recent development

Review on ultrasonic fabrication of polymer micro devices.

A review on microfabrication of thermoplastic polymer-based microneedle arrays

Micro injection molding processing of UHMWPE using ultrasonic vibration energy

Abstract Precision injection molding is the most efficient mass production technology for manufacturing plastic optics. Applications of plastic optics in field of imaging, illumination, and concentration demonstrate a variety of complex surface forms, developing from conventional plano and spherical surfaces to aspheric and freeform surfaces. It requires high optical quality with high form accuracy and lower residual stresses, which challenges both optical tool inserts machining and precision injection molding process. The present paper reviews recent progress in mold tool machining and precision injection molding, with more emphasis on precision injection molding. The challenges and future development trend are also discussed.

Precision injection molding of freeform optics

Ultrasonic hot embossing has been developed in recent years enabling quick and flexible fabrication of micro structures from thermoplastic polymers. This paper describes many possibilities of the fabrication, use, and limits of tools for this process. Tools have been produced by milling, drilling, silicon etching, photo and X-ray lithography, and electroplating and by combining these processes.

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Tools for ultrasonic hot embossing

Microstructures are fabricated from polymer foils in seconds by a new process called ultrasonic hot embossing. This process allows to realize new designs within a day and is suitable both for large- and small-scale production. The required investment costs are in the order of some 10,000 ź. In this paper, heat generation and distribution in ultrasonic hot embossing is investigated with piezo-electric and pyro-electric foils from the polymer polyvinylidene fluoride (PVDF) placed into a stack of polymer layers. This way, the influence of pre-structures on and powders between polymer layers is revealed.

Heat generation and distribution in the ultrasonic hot embossing process

Nozzles with circular cross-section and a diameter varying in axial direction have been fabricated in a microfluidic channel from polyvinylidene fluoride as chemically resistive thermoplastic polymer. Smallest diameter and length of the nozzle are approximately 150 µm and 3.4 mm, respectively. The nozzle and the entire channel system have been fabricated from two halves generated by ultrasonic hot embossing and bonded to each other by ultrasonic welding. Alignment during ultrasonic welding was assisted by a fit of energy directors and an accuracy of 35 and 10 µm in normal and lateral direction, respectively, was obtained. Thermoplastic molding of the two halves of the channel structures was performed by ultrasonic hot embossing with a cycle time of a few seconds. The development was significantly accelerated by milling the tools directly into aluminum plates. This way, new designs were realized within a day. The micro nozzles have been proven generating liquid/liquid dispersions of different flow patterns as a function of flow velocity and Capillary number.

Ultrasonic fabrication of micro nozzles from a stack of PVDF foils for generating and characterizing microfluidic dispersions

Electronic circuit boards have been fabricated in cycle times of a few seconds by ultrasonic fabrication. A stack of thermoplastic polymer foils with a copper layer, 20 μm in thickness, on top is transformed into a polymer carrier with separated conductor paths. This process is accomplished in cycle times of a few seconds and the required equipment is just a commercially available ultrasonic welding machine and a metal tool micro patterned, e.g., by milling.Since soldering is often not possible on a thermoplastic carrier, electronic components are joined to the conductor paths by ultrasonic welding. This is achieved by employing an anisotropic conductive foil containing metal particles providing the electrical contact normal to the foil and showing no conductivity in lateral direction. The anisotropic conductive foil also serves as glue between circuit board and electronic components.

S. Liao

Papers

Review on ultrasonic fabrication of polymer micro devices.

Tools for ultrasonic hot embossing

Heat generation and distribution in the ultrasonic hot embossing process

Ultrasonic fabrication of micro nozzles from a stack of PVDF foils for generating and characterizing microfluidic dispersions

MID Fabricated by Ultrasonic Processing