Using Micromachined Molds, Partial-curing PDMS Bonding Technique, and Multiple Casting to Create Hybrid Microfluidic Chip for Microlens Array

Abstract

In a previous study, we presented a novel manufacturing process for the creation of 6 × 6 and 8 × 8 microlens arrays (MLAs) comprising lenses with diameters of 1000 μm, 500 μm, and 200 μm within an area that covers 10 mm × 10 mm. In the current study, we revised the manufacturing process to allow for the fabrication of MLAs of far higher density (15 × 15 and 29 × 29 within the same area). In this paper, we detail the revised manufacturing scheme, including the micromachining of molds, the partial-curing polydimethylsiloxane (PDMS) bonding used to fuse the glass substrate and PDMS, and the multi-step casting process. The primary challenges that are involved in creating MLAs of this density were ensuring uniform membrane thickness and preventing leakage between the PDMS and glass substrate. The experiment results demonstrated that the revised fabrication process is capable of producing high density arrays: Design I produced 15 × 15 MLAs with lens diameter of 0.5 mm and fill factor of 47.94%, while Design II produced 29 × 29 MLAs with lens diameter of 0.25 mm and fill factor of 40.87%. The partial-curing PDMS bonding system also proved to be effective in fusing PDMS with glass (maximum bonding strength of approximately six bars). Finally, the redesigned mold was used to create PDMS membranes of high thickness uniformity (coefficient of variance <0.07) and microlenses of high lens height uniformity (coefficient of variance <0.15).

Polymer Microchannel and Micromold Surface Polishing for Rapid, Low-Quantity Polydimethylsiloxane and Thermoplastic Microfluidic Device Fabrication

“…Recently, polymer-based micromold has been proposed as a simple alternative to silicon or SU-8 micromold for microfluidic chip fabrication. Polymer micromolds are fabricated through CNC milling [30], laser ablation [31], or 3D printing [32,33]; these are straightforward methods with low-cost desktop fabrication facilities. Such facilities also require fewer operating skills, enabling broad usage [3,34].…”

Research on Integrated 3D Printing of Microfluidic Chips

“…At the same time, mature polymer hot presses on the market are small and need to be customized or self-developed [ 27 , 28 ]. Plasma bonding requires rapid and accurate alignment and bonding of microchannels after the surface modification of the base material is completed, which requires high-operation technology [ 29 ]. High-temperature bonding requires a muffle furnace to reach temperatures of more than 500 °C, and then annealing to achieve bonding.…”

Study of PDMS Microchannels for Liquid Crystalline Optofluidic Devices in Waveguiding Photonic Systems

“…Importantly, a mold with sufficient quality and specific geometry is needed to fabricate optofluidic structures in PDMS using a casting technique. There are many methodologies to manufacture molds [11], including 3D printing [12][13][14], micromilling [11,12,15,16], and capillary film processing [17]. In the same context, photolithography is the most widely used for complex and precise structures [18,19].…”