Machining technologies and structural models of microfluidic devices

Abstract

In the past decades, microfluidic chips have been one of the hottest research topics in the “lab-on-a-chip” field. However, it is still a challenge for design the perfect microchannels with high functional integration, complex geometry, and high production efficiency. This review paper provides a comprehensive overview of microfluidic structural models and designs, manufacturing techniques, and bonding methods. The effect of three types of microfluidic channel structure models and their configuration parameters on the fluid behaviors of microfluidics was investigated. Surface-to-volume ratio of the flow channel is a critical parameter for determining the mixing and diffusion capabilities of the microfluidic devices (MDs). Thereafter, the main manufacturing techniques for microstructures were discussed, including etching, photolithography, soft lithography, molding, mechanical micro-machining, laser beam micromachining, printing, and 3D printing. We performed a statistical analysis to discuss the relative advantages and disadvantages of these manufacturing methods. In addition, the current bonding methods for MDs were also summarized, including thermal bonding, solution adhesive bonding, dry adhesive bonding, plasma bonding, and anodic bonding. a comparison of different bonding methods was presented to provide a reference to select a suitable bonding method for the assembly of microfluidic device. Finally, the tendencies and challenges of microchannel manufacturing were discussed, and the prospects were also provided.

Establishment and evaluation of on-chip intestinal barrier biosystems based on microfluidic techniques

“…Unfortunately, the optically opaque nature of silicon makes optical imaging and analysis difficult. In contrast, glass exhibits excellent optical transparency, lower cost, higher resistance to high temperature and greater elasticity to high pressures [ 63 , 65 ]. The main concern is that the use of amorphous glass results in anisotropic structures with a high-aspect-ratio [ 66 ].…”

“…Over the past few decades, multiple microfabrication technologies, including photolithography, milling and laser cutting, molding [ 65 , 101 , 102 ] and 3D printing technology, have been successfully applied for the construction of in vitro intestinal barrier models. In this part, we will introduce these established technologies in detail.…”

“…The molding processing technique can be divided into hot embossing and injection molding according to process principles [ 65 ]. Hot embossing is a relatively simple manufacturing process for replicating microchannels on a mold by applying force and temperature onto substrates such as silicon, glass, and polymer materials.…”

“…Injection molding constitutes a process wherein the thermoplastic material is initially subjected to uniform plasticization within a heated barrel, followed by its forced introduction into the confines of a pre-closed mold cavity via a plunger or a reciprocating screw mechanism [ 65 ]. Subsequently, the material is allowed to solidify and take the shape of the mold through the application of cooling mechanisms, culminating in the formation of the desired molded component.…”