Entity

Time filter

Source Type

Binghamton, NY, United States

Jena R.K.,Alliance for Manufacturing and Technology | Jena R.K.,Nanyang Technological University | Yue C.Y.,Alliance for Manufacturing and Technology | Yue C.Y.,Nanyang Technological University | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2011

This paper reports on the development and application of a permanent surface modification technique (photo-grafting) as an improved method for bonding COC (TOPAS) microfluidic substrates with a cover plate without affecting the channel integrity. This technique not only helps to increase the bond strength of the original device but also makes the surface hydrophilic which is essential for quick fluid flow while passing analytes through the device. The bond strength of the modified and unmodified chips was measured using the tensile and peel tests. It was observed that the bond strength of the modified chips has increased approximately 6 times to 1.18 (±0.08) MPa compared to 0.21 (±0.05) MPa for the unmodified chip. The modified surface was evaluated using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and water contact angle measurement. The contact angle of the modified surface decreased to 20 ± 5° from 85 ± 3° for the untreated substrate. Scanning electron microscope and confocal microscope examinations of cross-sectional profiles of the bonded chips indicated that the integrity of the channel features was successfully preserved. © 2011 Elsevier B.V. Source


Jena R.K.,Alliance for Manufacturing and Technology | Jena R.K.,Nanyang Technological University | Yue C.Y.,Alliance for Manufacturing and Technology | Yue C.Y.,Nanyang Technological University | Yun K.X.,Nanyang Technological University
RSC Advances | Year: 2014

In recent years, polymer based microfluidic devices have become more widespread with the driving force being the development of inexpensive disposable analytical devices. Hot embossing and injection moulding are the two promising techniques that are widely used for micro-fabrication of polymeric substrates because identical devices can be mass produced using a master/mold. However, the major problem with these techniques is the time and expense needed to produce a stamping tool (mold) which can withstand the temperature and stress of the fabrication process over multiple cycles. To overcome this problem, we have developed an epoxy toughened nanocomposite mold material, which is relatively inexpensive compared to the commonly used metallic glass mold material. Our molds can be produced with ease, and are sufficiently durable to withstand multiple embossing cycles. Moreover, compared to other mold materials, very high aspect ratio microchannels can be replicated. We have characterized the morphological, physical and thermomechanical properties of this new nanocomposite mold material including its surface morphology, roughness and friction coefficient. Finally, the performance of the nanocomposite mold to fabricate microdevices using a cyclic olefin copolymer (COC) by the hot embossing and injection molding techniques was assessed. This mold material was found to be suitable for fabricating polymeric microdevices with high channel integrity. © 2014 The Royal Society of Chemistry. Source


Jena R.K.,Alliance for Manufacturing and Technology | Jena R.K.,Nanyang Technological University | Chen X.,Alliance for Manufacturing and Technology | Chen X.,Nanyang Technological University | And 3 more authors.
Journal of Micromechanics and Microengineering | Year: 2011

Transparent, amorphous cyclic olefin copolymers (COCs) have been frequently used for the fabrication of microfluidic devices using a hot embossing technique for numerous applications. In hot embossing, the polymer is deformed near its glass transition temperature (Tg), i.e. between Tg and Tg + 60 °C where the viscoelastic properties of the material are dominant. The proper characterization of the viscoelastic properties is of interest as this can lead to a better understanding of polymer flow behaviour during microfabrication. Furthermore, the ability to model its rheological behaviour will enable the prediction of the optimal hot embossing processing parameters. We performed small amplitude oscillatory shear experiments on four grades of COCs, TOPAS-8007, TOPAS-5013, TOPAS-6015 and TOPAS-6017, in order to characterize their flow behaviour. The experiments were conducted within the frequency range from 0.01 to 500 Hz at between Tg + 20 and Tg + 60 °C. The flow properties could be represented using a generalized Maxwell viscoelastic constitutive model with Williams-Landel-Ferry-type temperature dependence. Good fit of the experimental data was obtained over a wide range of temperatures. The model could be coupled with ABAQUS finite element software to predict the optimal conditions for fabricating a capillary electrophoresis micro-chip on a TOPAS-5013 substrate by hot embossing. © 2011 IOP Publishing Ltd. Source


Jena R.K.,Alliance for Manufacturing and Technology | Jena R.K.,Nanyang Technological University | Taylor H.K.,Alliance for Manufacturing and Technology | Taylor H.K.,Massachusetts Institute of Technology | And 7 more authors.
Journal of Micromechanics and Microengineering | Year: 2011

The hot embossing process has been identified as a promising technique for fabricating micro- and nanostructures for polymer-based biological and chemical MEMS (micro electro mechanical systems). However, there has not been any investigation of the effect of polymer chain orientation in the base polymer substrate on replication during the micro-embossing process. Such effects could prove important because polymer chain orientation may develop in the polymer substrates during their production. In this investigation, it was observed that the degree and ease of microchannel replication are significantly influenced by the molecular chain orientation in injection-molded polymer substrates. Microchannels aligned along the flow direction of the polymer replicate easily compared to microchannels aligned across the flow direction of the polymer. The replication fidelity during hot embossing was investigated using a white-light confocal microscope. The anisotropy of injection-molded polymer plays a dominant role in the replication fidelity of microchannels, and the ability to model the anisotropic behavior of the material will enable understanding and prediction of the hot embossing process. Therefore, a material model that reflects the directionality was utilized to simulate the experimental embossing results obtained both along and across the flow direction of the polymer. By comparing experimental results with simulations, we observed that the model is reasonably realistic. © 2011 IOP Publishing Ltd. Source


Jena R.K.,Alliance for Manufacturing and Technology | Jena R.K.,Nanyang Technological University | Chester S.A.,Alliance for Manufacturing and Technology | Chester S.A.,Massachusetts Institute of Technology | And 8 more authors.
Sensors and Actuators, B: Chemical | Year: 2011

Amorphous cyclic olefin copolymers (COCs) are beginning to be used for making microfluidic devices for life science applications. Typically, both micro-scale and nano-scale channels are imprinted onto the copolymer by hot embossing. However, optimal manufacturing process conditions will only be possible if the COCs thermo-mechanical behavior is experimentally well characterized, mathematically modeled, and implemented in a numerical simulation. We have conducted large-strain compression experiments on two commercial grades of COCs: TOPAS-8007, and TOPAS-6015 in a wide temperature, and strain rate range. A constitutive theory and numerical implementation developed by Srivastava et al. [1] was applied to model the behavior of TOPAS. We have employed that numerical implementation, together with the material parameters for TOPAS determined here, to predict the response of TOPAS in the following microfluidic fabrication operations: (i) micro-scale hot embossing on TOPAS-8007 to replicate a micro-chip; and (ii) for sealing the channels in the micro-chip: (a) thermal bonding of an embossed chip of TOPAS-8007 with a cover plate of TOPAS-8007; and (b) thermal bonding of an embossed chip of TOPAS-6015 with a cover plate of TOPAS-8007. We show that the model can provide a simulation capability for estimation of the processing parameters for hot embossing and thermal bonding. © 2010 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations