Low-temperature direct bonding of glass nanofluidic chips using a two-step plasma surface activation process

Abstract

Owing to the well-established nanochannel fabrication technology in 2D nanoscales with high resolution, reproducibility, and flexibility, glass is the leading, ideal, and unsubstitutable material for the fabrication of nanofluidic chips. However, high temperature (~1,000 °C) and a vacuum condition are usually required in the conventional fusion bonding process, unfortunately impeding the nanofluidic applications and even the development of the whole field of nanofluidics. We present a direct bonding of fused silica glass nanofluidic chips at low temperature, around 200 °C in ambient air, through a two-step plasma surface activation process which consists of an O(2) reactive ion etching plasma treatment followed by a nitrogen microwave radical activation. The low-temperature bonded glass nanofluidic chips not only had high bonding strength but also could work continuously without leakage during liquid introduction driven by air pressure even at 450 kPa, a very high pressure which can meet the requirements of most nanofluidic operations. Owing to the mild conditions required in the bonding process, the method has the potential to allow the integration of a range of functional elements into nanofluidic chips during manufacture, which is nearly impossible in the conventional high-temperature fusion bonding process. Therefore, we believe that the developed low-temperature bonding would be very useful and contribute to the field of nanofluidics.

Extended Nanofluidic Immunochemical Reaction with Femtoliter Sample Volumes

“…We utilized low‐temperature bonding in order to avoid heat‐associated destruction of functional molecules during thermal bonding. This method enables glass‐glass bonding at 25–100 °C by oxygen plasma surface activation involving fluorine.…”

“…After permanent glass bonding, patterning is difficult in the closed channels, which are not easily accessible from the outside. Low‐temperature (25–100 °C) bonding methods recently developed by our group avoid thermal destruction because the principle is based on chemical bonding between silanol groups without heat; however, the oxygen plasma irradiation surface activation process decreases the activity of modified functional molecules.…”

Low temperature direct bonding of silica glass via wet chemical surface activation

“…Before the activation treatment, all samples were initially passed through a proprietary multistage bath cleaning process. First, the glass pieces were rinsed in acetone and methanol with ultrasonic assistance for 8 Notably, during each process, we carefully washed the samples under running DI water to remove any residue from the previous procedure and then kept the samples in DI water for the next procedure.…”

Interfacial Phenomena and Fluid Control in Micro/Nanofluidics

“…[58][59][60][61][62][63][64][65] Many well-written review articles have been published on the subject of droplet flow. 9,[66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] In this review, parallel two-phase flow 6,[82][83][84][85] is considered with respect to the roles of liquid interfaces for the sake of simplified physical descriptions.…”