Ultrasonic Fusion Bonding For Polymer Microfluidic Chips

Polymers play important role in microfluidic chips in recent years. They have lots of advantages such as low cost, a broad range of material, comparatively simple process and good biological compatibility. Polymer microfluidic chips have become a research hotspot. Bonding is a last and key step in the fabrication process of microfluidic chips which properties own much to bonding quality, and it is also important part to realize microfluidic chips form study to application and mass production. Traditional bonding methods of thermoplastic polymer microfluidic chips contain direct heating and interstitial bonding. But there are many problems when using these methods, such as low processing efficiency and bonding strength, hard to realize mass production and so on.A novel bonding method, ultrasonic welding technology, applied to polymer microfluidic chips bonding has advantages such as short bonding time, high strength and with no other material to introduce and so on, and so it has a prospect with large scale production for polymer microfluidic chips. But there are also many problems while introducing the macro technology into the micro area. Ultrasonic fusion bonding has a high strength after welding, but how to design a reasonable welding joint for microfluidic chip to gain a successful bonding is a key problem. In order to solve this problem, the paper presented two kinds of novel bonding joints based on the general principles of design in welding joints of macro plastic specimens and silicon-based process technologies, and their solid molds were fabricated by lithography and anisotropic wet etching technology. Modified the traditional routes of silicon-based technologies, solved the problems during spinning photoresist and finally obtained the two kinds of joints of silicon molds.Their substrates were fabricated by hot embossing. Modified hot embossing process, solved many problems appeared in hot embossing process and finally got the two kinds of substrates. Several reasonable design rules of ultrasonic bonding joints on microfluidic chips are obtained by analysis and comparison of the quality of ultrasonic bonding between the two kinds of bonding joints after ultrasonic bonding tests, which possesses guiding significance for ultrasonic welding joints design of polymer MEMS.