In the fabrication of microfluidic devices by hot embossing, secondary molds made from epoxy and other polymeric materials with high Tg are commonly used in lab-scale research and for short production runs of several hundred products. However, few studies have been conducted to compare the performance and efficacy of such molds compared to the master silicon mold. To allow such molds to be exploited fully, this study investigates the performance of silicon, epoxy and COC (TOPAS-6017 grade) molds to fabricate microchannels on COC (TOPAS-8007 grade) substrate using hot embossing. The degree of filling of the mold cavity during microfabrication was assessed. At the optimum embossing conditions (i.e. 100 °C, 2.94 kN load and 5 min loading time), all three molds had similar performance in terms of replication fidelity. However, at sub-optimum conditions (e.g. 80 °C), the silicon mold was the best in terms of mold cavity filling followed by COC and epoxy. For surface roughness and friction coefficient which are important factors affecting tool life, it was found that epoxy mold gives the lowest values followed by COC and silicon. The surface energy determined using contact angle measurements gave a similar trend with epoxy having the lowest surface energy (28 dyne/cm), followed by COC (33.52 dyne/cm) and silicon (71.63 dynedyne/cm). A lower surface energy will result in lower adhesion and friction coefficient between the polymer and mold, resulting in easier demolding.

Comparison of different molds (epoxy, polymer and silicon) for microfabrication by hot embossing technique

The roll-to-roll (R2R) hot embossing process is a recent advancement in the micro hot embossing process and is capable of continuously fabricating micro/nano-structures on polymers, with a high efficiency and a high throughput. However, the fast forming of the R2R hot embossing process limits the time for material flow and results in complicated flow behavior in the polymers. This study presents a fundamental investigation into the flow behavior of polymers and aims towards the comprehensive understanding of the R2R hot embossing process. A three-dimensional (3D) finite element (FE) model based on the viscoelastic model of polymers is established and validated for the fabrication of micro-pyramids using the R2R hot embossing process. The deformation and recovery of micro-pyramids on poly(vinyl chloride) (PVC) film are analyzed in the filling stage and the demolding stage, respectively. Firstly, in the analysis of the filling stage, the temperature distribution on the PVC film is discussed. A large temperature gradient is observed along the thickness direction of the PVC film and the temperature of the top surface is found to be higher than that of the bottom surface, due to the poor thermal conductivity of PVC. In addition, creep strains are demonstrated to depend highly on the temperature and are also observed to concentrate on the top layer of the PVC film because of high local temperature. In the demolding stage, the recovery of the embossed micro-pyramids is obvious. The cooling process is shown to be efficient for the reduction of recovery, especially when the mold temperature is high. In conclusion, this research advances the understanding of the flow behavior of polymers in the R2R hot embossing process and might help in the development of the highly accurate and highly efficient fabrication of microstructures on polymers.

https://iopscience.iop.org/article/10.1088/0960-1317/25/6/065004/pdf

Flow behavior of polymers during the roll-to-roll hot embossing process

The development of a one-step process for producing high fidelity hot-embossed cyclic-olefin co-polymer (COC) based microfluidic devices without the need for pre-annealing the base polymer substrate/film is outlined. This was achieved through proper selection of the hot-embossing conditions that was based on an in-depth understanding of the fundamental factors which affect the replication accuracy of microchannels during the hot-embossing process. An important factor that is commonly overlooked in the hot-embossing of films (typically with thicknesses less than 1 mm) is the existence of polymer chain orientation. Generally, polymer films used for hot-embossing are not pre-annealed to minimize residual stresses and remove any chain orientation that may be present, and this affects the replication accuracy. In contrast, polymer substrates (typically with thicknesses more than 1 mm) that are used for hot-embossing to produce microfluidic devices need to be pre-annealed to minimize residual stresses and remove any chain orientation. Processing of the latter thus required an additional step. The avoidance of such pre-annealing may affect the replication accuracy. In the present work, it was demonstrated that microfluidic devices with high fidelity microchannels could be produced using a single-step hot-embossing process based on knowledge of the influence of embossing temperature, embossing pressure, embossing time and polymer chain orientation in the film/substrate on micro-replication.

High fidelity hot-embossing of COC microdevices using a one-step process without pre-annealing of polymer substrate

Hot embossing molding is a promising method to fulfill fabrication of microstructures. The surface flatness of a hot embossing tool is the key parameter affecting the transcription rate significantly of the micro-hot embossing process. This study demonstrated a technology for fabricating a precision hot embossing tool using hybrid materials. The silicone rubber mold was chosen as a bridge tooling, which is the key process for fabricating a precision hot embossing tool using hybrid materials. The mold plate can improve the surface flatness of the fabricated hot embossing tool during post-curing. The surface flatness of the hot embossing tool around 46.38% can be improved and a cost reduction around 69.61% can be achieved.

Development of a precision hot embossing tool with microstructures for microfabrication

The embossing of polymeric materials is widely used for manufacturing of micro-parts. The thermoplastic amorphous polymers are always selected to get micro-components. The paper consists to characterise the thermal mechanical properties of three amorphous polymers: polystyrene (PS), poly(methyl methacrylate) (PMMA) and polycarbonate (PC). A set of experiments such as differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) have been carried out with PS, PMMA and PC. The thermoplastic polymers’ behaviours have been characterised above their glass transition temperature. Then, flexible micro-fluidic devices have been manufactured with the polymers by hot embossing process. The surface topography of mould die cavity insert and the micro-fluidic devices have been observed and analysed by a 3D optical microscopy viewing and measurement system in order to compare the replication accuracy for polymeric replicas. The surface roughness of the micro-fluidic devices has been measured to characterise the effect of the compression load and temperature in the hot embossing process. The paper is mainly concentrated on the effect of the process parameters with different amorphous thermoplastic polymers to achieve the process optimization. The results concerning the micro- and nano-scale cavities filling provide information on the reliability about the facilities to replicate complex surface topographies. In this paper, the flow behaviour of polymer during forming process thus process parameters would be investigated. The mould instrumented with micro-structured patterns will be presented. The relationship between embossing conditions and parts quality will be established.

Process parameter effects on dimensional accuracy of a hot embossing process for polymer-based micro-fluidic device manufacturing

A parameter study on the micro hot-embossing process of glassy polymer for pattern replication

If a vibration module is added on laser machining system, the quality of surface finish and aspect ratio on metals can be significantly enhanced. In this study, a single mobility model of vibrating laser along the path of laser beam was put forward. In order to realize the desired unidirectional motion, a resonance type vibration module with optical lens was designed and manufactured. This cylindrical module was composed of curved-beam flexure elements. The cylindrical coordinate system was established to describe the relationship of a curved-beam flexure element’s motion and deformation. In addition, the stiffness matrix of the curved-beam element was obtained. Finite element method and dynamical modeling were provided to analyze the resonance frequency and the displacement of the motion. The feasibility of the design was demonstrated with the help of experiments on frequency response. Experimental results show good agreement with theoretical analysis and simulation predictions.

Design and verification of a novel hollow vibrating module for laser machining

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

EunHee Kim

Author Tools

Chat about Author

Papers

A parameter study on the micro hot-embossing process of glassy polymer for pattern replication

Design and verification of a novel hollow vibrating module for laser machining