Abstract
Injection molding is one of the main techniques for manufacturing microfluidic chips. As an important stage, the demolding process in injection molding will directly affect the quality of the functional unit of microfluidic chips (polymer microchannels), thus limiting the realization of its functions. In this study, molecular dynamics (MD) simulations on the demolding process were carried out to investigate the influence of diamond-like carbon (DLC) coating on the channel deformation. The channel qualities of polystyrene (PS), polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC) and polycarbonate (PC) were analyzed after demolding with nickel (Ni) and DLC-coated mold inserts, respectively. In particular, the non-bonded interfacial interaction energy, elastic recovery and gyration radius of polymer molecular chains were further studied. The results showed that the non-bonded interfacial interaction energies could be significantly reduced by DLC-coating treatment on the mold insert. Moreover, common channel defects such as molecular chain separation, surface burrs and necking did not occur. The treatment of DLC coating could also significantly reduce the change in the gyration radius of polymer molecular chains, so the morphology of the polymer channel could be maintained well. However, the change in the elastic recovery of the polymer channel was increased, and the opening width became larger. In a word, DLC-coating treatment on the mold insert has great application potential for improving the demolding quality of injection-molded microfluidic chips.
Highlights
Microfluidic chips have been widely used in life science, chemical analysis, medical detection and other fields [1]
The molecular dynamics (MD) method was used to simulate the demolding process of polymer PS, polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC) and PC on the Ni and diamond-like carbon (DLC)-coated mold inserts
The non-bonded interfacial interaction energy, elastic recovery and gyration radius were analyzed to find out the influence of DLC coating on improving the demolding quality of the polymer channel under the external demolding force of
Summary
Microfluidic chips have been widely used in life science, chemical analysis, medical detection and other fields [1]. The main functional structure of the microfluidic chip is the microchannel, as to complete fluid filling, sample separation and detection. The performance of the microfluidic chip largely depends on the replication quality of these channels. Injection molding technology is one of the main methods for microfluidic chip manufacturing [2], which has the advantages of high precision, low cost, high efficiency, and short cycle [3]. Its process mainly includes four stages as the filling, the packing, the cooling and the demolding. The demolding process plays an important role in the high-quality replication of the microchannels
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