Low-cost microfluidic diagnostics based on paper and thread

The research reported in this thesis focuses on the development of a new class of microfluidic sensing devices for biomedical analysis. The distinctive aspect of these devices is that they are made of low-cost and universal materials, such as paper and thread. The intended applications of the low-cost microfluidic devices are predominantly for human healthcare, rapid disease detection and large scale disease screening in developing regions of the world where medical facilities and healthcare situations are much more challenging than in the developed world. The potential of microfluidics in analytical and diagnostic fields has been demonstrated by a very large number of fundamental and application studies in the last couple of decades. However, most of highly sophisticated micro- and nano-fluidic diagnostic techniques are unable to meet the challenges of healthcare and disease screening in resource-limited developing regions in the world, as they are either too expensive or require trained personnel to operate. Since more than two-thirds of the world’s population live in the developing countries and most of them are in resource-limited regions, there is an urgent need for low-cost, portable, rapid and electronically transmittable diagnostic methods and devices to be developed in order to significantly increase the accessibility of healthcare by people living in these regions. This thesis has two parts, which separately present research work in paper-based and thread-based microfluidic devices. In the first part, research into paper-based microfluidics combines novel scientific ideas with traditional techniques and know-how in papermaking and printing. Liquid sample transport in these devices can be controlled by using channels chemically defined on paper via printing cellulose-reactive reagents. An interesting difference and novelty of this research compared with the research reported by other groups is that it uses well-known papermaking know-how (e.g. internal paper sizing) and ink jet printing technology, to create capillary-driven microfluidic devices. Biochemical detection chemistries can be printed into the designated detection zones of paper-based microfluidic devices. Another original concept explored by this thesis is the building of sample flow control switches and reactors on paper, enabling multi-step analyses to be performed on paper. Applications of paper-based microfluidic systems for semi-quantitative and quantitative biochemical analyses are demonstrated in the thesis. In the second part, innovations in using thread as a flexible and versatile material for microfluidic diagnostics are presented. Bioactivity can be relatively easily introduced onto threads; thread-based microfluidic devices can be simply fabricated by sewing bioactive threads onto suitable supporting materials using a household needle or a sewing machine. This part also demonstrates potential applications of the thread-based microfluidic devices not only in semiquantitative biochemical analysis, but more importantly, in real-life diagnositics such as blood grouping tests. This work shows that the bioactive thread-based microfluidic concept will serve as a platform that allows other healthcare diagnostic devices to be developed. It is the sincere hope of the author that one day the findings presented in this thesis will be able to serve communities in the developing world by providing solutions to their problem with healthcare and disease control.