Polymer welding offers alternative to adhesives

Edited by the Engineeringtalk editorial team Aug 21, 2006

Mask welding system enables the joining of intricate microfluidic plastic components.

Swiss manufacturer Leister Process Technologies has developed a mask welding system that enables the joining of intricate microfluidic plastic components.

This system, known as the Novolas micro, provides exciting opportunities for the development of improved production methods and techniques deployed in the medical, biotechnology and pharmaceutical sectors.

Leister have recently appointed Horizon Instruments as the authorised distribution and service centre for all Novolas laser systems for the UK and Ireland.

The key features of the Novolas mask welding process are: outstanding micron precision and detail combined with optimum strength, fully automated alignment of mask with part, high reproducibility and the ability to join very fine 2D structures.

Polymer welding offers a superior alternative to adhesives, eliminating the common problems of particulates and undesirable chemical interactions.

Leister states: "The research and development of microfluidic devices (so called lab-on-a-chip technology) is one of the fastest growing areas of medical and biological diagnostics for a variety of applications including DNA analysis, drug discovery and clinical diagnostics".

"Up to now, the preferred materials have been silicon, glass or quartz, mainly because micro fabrication methods for these materials have been extensively developed in the microelectronics industry".

"However, for many applications, these materials, and associated fabrication processes, are not cost-effective for commercial production and [are typically used] for single use devices".

Plastics are now playing an ever increasing role in micro-technology, especially in low-cost, mass-produced applications.

Plastics like polymethylmethacrylate (PMMA), polycarbonate (PC) and cyclopolyolefinpolymere (COC) have been intensively investigated because of their resistance to certain chemicals and their biocompatibility.

Traditional joining procedures for plastic parts include glue cured by heat or UV light, ultrasonic welding and hot gas welding.

However, most of these methods cannot easily be adapted to micro structured plastic parts due either to adhesive dispensing problems and the chemical and surface properties of the adhesives or, with the latter methods, the generation of particulates and the lower precision of energy transfer.

Although laser welding of plastics was developed in the 1960s it has only recently become a cost-effective technology offering the advantages of noncontact and localised energy input by laser beam.

Moreover, recent progress in semiconductor laser technology coupled with the development of compact, economical and reliable laser sources in the NIR range (700 to 1500nm), have promoted the use of laser welding as an effective and viable alternative for joining microfluidic devices.

The benefits of the Novolas mask welding system can be applied to a wide range of medical, biological and pharmaceutical applications, typically wherever intricate components require joining with excellent welding quality, high precision and high reproducibility.