Wet micro-embossing and alternative wax printing of paper for disposable lab-on-chip devices

• Main Author: Tang, Samuel Liang Hao.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/53546
• Institution: Nanyang Technological University

Research done on paper based microfluidic has been escalating since 2007 as paper is because attractive substrate for making microfluidic devices. There are several advantages of using paper as a substrate over other materials such as glass or plastic. Paper has the inherent ability to transport fluids via capillary forces without the need for external pumps and valves. Paper is also cheap, easily available, and biocompatible. Applications of paper based microfluidics include health diagnostic, environmental monitoring and food quality testing. As paper based microfluidic are claimed to be low-cost and equipment-free, it is an attractive device for usage in developing countries. The main focus of this research project is to study and explore new fabrication methods for paper-based microfluidic devices. There are currently three main patterning principles used in the fabrication of paper-based microfluidic devices and they are physical blocking of pores in paper, chemical modification of the fibre surface and physical deposition of reagent on fibre surface.[2] Attempts were made to fabricate a paper-based microfluidic device with a selective reduction of pore sizes in paper by embossing with a stamp. The student obtained different set of results when the paper was soaked and immediately embossed as compared to when the paper was soaked, left to dry and later embossed. When the paper is soaked and immediately embossed, the rate of wicking in the non-compressed region is much faster than wicking which took place in the compressed region. However, when the paper was first soaked, left to dry and later embossed, the rate of wicking in both the compressed and non-compressed regions is the same. Another fabrication method for microfluidic devices involves the use of wax as a physical deposition of reagent on fibre surfaces. Wax printing to create microfluidic device was first developed by the Whitesides Group of Harvard University.[3] The wax printing fabrication method by the Whitesides Group involves creating the design layout for wax on paper, printing the wax on paper and then followed by reflowing of wax on paper. In this project, the student came out with a variant design for wax printing on paper. The variant design that the student came out with involves the creation of a template where the area under the template will be used to create the hydrophilic area for the microfluidic device. Molten wax is poured over the surrounding area of the template to create the hydrophobic area. This report will include the investigation of the optimal temperature for molten wax to be deposited on the paper surface for complete impregnation of wax through the thickness of the paper. This proof of concept was successful and suggestions for further research and developments were highlighted.