Flexible Inserts for Injection Molding of Complex Micro‐Structured Polymer Components

Abstract

Mass production of microfluidic devices commonly relies on injection molding. Injection molding requires a master surface made using micro or nanofabrication. Conventionally, electroplating from a silicon master is used for mold insert production, but this is expensive and cannot be used with masters produced via the Bosch process as interlocking of the scalloping between polymer and metal insert hinders part ejection. Here, an alternative to the electroplating process is developed by adapting a nanoimprint route to produce flexible micro-structured polymer inserts capable of molding using a Bosch process-produced master. An optimized fabrication approach using silicon masters with smooth sidewalls (produced using the mixed process) is used to characterize the limits of the process. Aspect ratios of 1 and below are successfully replicated. Feature spacings down to 20 μm are successfully produced with minimal variation between repeated parts. Masters produced using two different Bosch etches exhibiting both coarse and fine nanometer scalloping are also studied. Parts are successfully ejected with retained nanometer scalloping in all samples although inlay damage occurred after >10 replicas. A proof-of-concept microfluidic device is successfully produced vindicating the use of this approach as an efficient and cost-effective approach for the rapid prototyping of complex micro-structured designs.

Optimisation of interlocking microstructured adhesive joints via finite element modelling, design of experiments and 3D printing

“…To enable direct comparison with the model, experiments were conducted to study the effect of feature width on the joint performance, with feature widths of 50 μm and 100 μm used for testing. The microstructured interfaces were produced using the micro-fabrication and injection moulding protocol utilised in the previous study and polycarbonate was retained as the adherend material [18]. During the micro-fabrication process, anisotropic reactive ion etching was utilised to define the feature height in the silicon master.…”

“…In our recent work (Hamilton et al [17]), the scope of the interlocking adherend work was expanded by developing an alternative adhesive single lap joint comprising micron scale interlocking square wave microfeatures within polycarbonate adherends. This was achieved via a photolithography based microfabrication approach in conjunction with injection moulding [18] (this methodology was also deployed recently in studies of the friction [19] and contact stiffness [20] of non-bonded interfaces). For the bonded interlocking interfaces, mechanical strength and work-to-failure improved by up to 95% and 162% relative to benchmark roughened planar specimens, respectively.…”

Protein-coated nanostructured surfaces affect the adhesion of Escherichia coli

“…In short, a master template with nanopatterns was made by electron beam lithography followed by a replication process using UV-based nanoimprint lithography (UV-NIL) (EV Group, Sankt Florian am Inn, Austria) into a working stamp material. 69 Injection moulding was performed using an Engel Victory 28 hydraulic injection moulding machine (Engel Austria GmbH, Schwertberg, Table 3 The characterisation of the nanopillars with interspace, diameter, and height (n = 5) Austria) to produce multiple polystyrene samples. 30 Each surface consisted of 7 × 4 repetitions of the pattern divided into three sections (total size 1 × 3 mm) with a different surface coverage: low (2.5%), medium (3.5%) and high (20%).…”

3D Printing and Rapid Replication of Advanced Numerically Generated Rough Surface Topographies in Numerous Polymers

“…These range from microinjection molding, milling, laser structuring, embossing, treatments and coatings, additive manufacturing, various lithography process methods, surface replication, etc. For example, injection molding or 3D printing can be used to fabricate surfaces for microfluidic devices [1,2] or MEMS. [3,4] Laser structuring can be employed to improve surface performance in areas such as optical devices, [5] solar cell design, [6,7] metallic joints, [8] biomedical surfaces and implants.…”

“…[34] The high accuracy has prompted researchers to explore its use in surface engineering to produce highly accurate replicas of micro and nanostructured topographies. [1,17] This makes the process ideally suited for the rough surface challenge being addressed in this work. However, there are many variables that can alter the performance of the injection molding process, and by extension, the quality of the components produced.…”