Film transfer and bonding techniques for covering single-chip ejector array with microchannels and reservoirs

Abstract

This paper describes a novel covering technique for an MEMS ejector array that is integrated with liquid reservoirs and microchannels on a single chip. The covering technique is based on wicking of a low viscous epoxy through the gap between the ejector wafer and a plate containing a parylene film, and allows the integrated ejector array to be fully covered by the parylene film with excellent uniformity, repeatability and yield. The technique is batch-processible and is suitable to cover many microfluidic systems with a thin film. The parylene film is tightly attached to the ejector array chip (with excellent bonding strength owing to the epoxy), so that liquid is automatically brought into the ejectors from the reservoirs through the microchannels (due to capillary force), as the ejectors shoot out liquid droplets. This automatic liquid supply makes the liquid level (in the ejector) be maintained constant throughout the entire ejection process until more than 90% of the liquid stored in the reservoir is delivered to the ejector through the microchannel. This paper describes also a number of other covering methods that we have experimentally tried, and compares those with the new covering technique.[1459]Index Terms-Acoustic droplet ejector, enclosed microchannels and reservoirs, epoxy wicking, film cover, integrated ejector array, microfluidic systems, parylene bonding.

Directional droplet ejection by nozzleless acoustic ejectors built on ZnO and PZT

“…Thus, it is important to maintain the liquid level constant during the ejection process, if one desires a uniform droplet size throughout the whole ejection process. We recently developed a technique to cover the ejection chamber, microchannel and reservoir so that the liquid level in the ejection chamber is maintained at a constant level through surface tension and capillary force [17].…”

“…Then, we need to make the SFAT capable of ejecting droplets of uniform size consistently from droplet to droplet. This will require the liquid level to be maintained at a constant level [17] throughout the whole ejection process. In this paper, the spatial accuracy of the ejector (as shown in figure 13) is not good, because of the environmental air flow and the varying liquid level during the ejection.…”

Plasma enhanced bonding of polydimethylsiloxane with parylene and its optimization

“…However, these methods cannot be used for bonding parylene with PDMS due to either ineffective bond qualities or degradation of the material. Other existing bonding methods for either materials result in poor adhesion between PDMS and parylene [31]. This lack of suitable bonding method has been a major impediment in the widespread use of both these materials in an integrated device.…”

Scalable bonding of nanofibrous polytetrafluoroethylene (PTFE) membranes on microstructures

“…Over the past years, a wide variety of polymers such as epoxies [26], SU-8 [27] and polyimide [28] have been used as the intermediate adhesive layer and their bonding strength as well as bonding robustness were investigated. Satyanarayana et al [29], for instance, demonstrated the so-called 'stampand-stick' transfer bonding method for adhesive bonding of microdevices using a UV curable adhesive.…”