The effects of placement and geometry on thermo-pneumatic pumping on centrifugal microfluidic compact disc (CD) platforms

Thermo-pneumatic pumping (TPP) is used to pump fluids on a microfluidic compact disc (CD) to the center of the CD. The expansion of air during heating drives the fluid transfer during TPP. It is easy to fabricate the TPP air chamber and adjoining channel since there are no moving components in their structure and that the thermal energy is supplied to the pump through localized heating equipment. This allows the pumping process even while the disc is rotating. In this report, by changing the shape and placement of the air chamber, we demonstrate that the experimental behavior of the TPP process can be manipulated by the altering heating rate of the air chamber. The placement and geometry of the air expansion chambers affect the rate of transfer during the TPP process. These modifications allow for the customization of the TPP and for a better incorporation onto the microfluidic CD platform, enabling the platform to be more versatile, more complex in functions and countable to be implemented. © 2012 IEEE

An overview of breast cancer diagnostic techniques / Mohammad Mahdi Aeinehvand

Breast cancer threatens many women, and early detection is a primary part of controlling and managing this disease. Mammography is widely used for the detection of breast cancer, but as this modality exposes women to ionizing radiation which can be a dangerous effect on their health, there are some doubts whether or not women under the age of 50 should be exposed to x-ray Mammography or not as a demand to detect breast cancer at early stages. Early detection of breast cancer plays a key role in rescuing lives which results in better quality of life. Many modalities used for detection of breast cancer still suffer some deficiencies such as the failure of mammography to detect 20%of the tumors, its uncomfortability to many of the patients in addition to considering it as a threatening source for the patients due to the increase of the possibility of cancer with the exposure repetition to the x-rays of the mammograms. Other modalities such as magnetic resonance imaging (MRI) and ultrasound are too expensive relatively. In this study a new technique using confocal microwave imaging (CMI) is studied. Breast tissue samples will be collected from department of surgery in UMMC. These samples will be subjected to study. Dielectric contrast between these samples will be determined based on their water content by utilizing the translucent characteristic of the breast. The tissue is to be determined whether it is cancerous or not using simple signal shifting, and summing and complex image composing algorithms is to be avoided. The permittivity values of normal and cancerous breast tissues also to be measured and compared. The digitized image of a cancerous breast tissue formed by hemispherical breast model using simple signal shifting is also to be studied

Reversible microballoon system for handling bioanalytical assays on centrifugal microfluidic platform / Mohammad Mahdi Aeinehvand

The unidirectional nature of centripetal flow, the predominant laminar flow in microfluidic systems, and the unreliability of the capillary valves are three main limitations exist in centrifugal microfluidics. This thesis presents the development of reversible microballoon pump, mixer and valve that enhance the control over the manipulation of liquids in bioanalytical assay on centrifugal microfluidic platforms. The high elasticity of the microballoon allows for an efficient conversion of centrifugally and externally induced forces to pumping, mixing and valving forces. The first liquid handling element presented in this thesis is a microballoon pump that relies on elastic energy stored in a latex membrane. It operates at low rotational speeds (< 1500 rpm) and pumps various liquid volumes towards the centre of the CD. The second presented liquid handling element is a microballoon mixer that operates by the expansion and relaxation of the membrane to provide for a consistent periodical 3D reciprocating flow. The third presented microballoon liquid handling element is a reversible thermo-pneumatic valve (RTPV) that seals or reopens an inlet when a trapped air volume is heated or cooled, respectively. It employs the deflection of a latex membrane to control liquid flow and prevent evaporation of reagents over a wide range of spinning speeds (up to 6000 rpm) and temperatures (up to the operational temperature of the disk materials), respectively. To illustrate their practicality in real life applications, microballoon pump, mixer, and valves are used for the actuation of a siphon channel, biosensing enhancement of dengue virus, and controlling fluid flow in a continuous liquid circulation process, respectively. Finally, an array of RTPVs and a microballoon pump/mixer are imbedded in a microfluidic cartridge to automate a lab protocol required for the multiplexing of temperature-controlled assays. As a pilot study, the cartridge is used for the conversion of multiple dengue virus RNA to cDNA, and reused for the preparation of multiple separated PCR reaction mixtures

A microfluidic Lab-on-a-Disc (LOD) for antioxidant activities of plant extracts

Antioxidants are an important substance that can fight the deterioration of free radicals and can easily oxidize when exposed to light. There are many methods to measure the antioxidant activity in a biological sample, for example 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity test, which is one of the simplest methods used. Despite its simplicity, the organic solvent that has been used to dilute DPPH is easily evaporated and degraded with respect to light exposure and time. Thus, it needs to be used at the earliest convenient time prior to the experiment. To overcome this issue, a rapid and close system for antioxidant activity is required. In this paper, we introduced the Lab-on-a-Disc (LoD) method that integrates the DPPH antioxidant activity test on a microfluidic compact disc (CD).We used ascorbic acid, quercetin, Areca catechu, Polygonum minus, and Syzygium polyanthum plant extracts to compare the results of our proposed LoD method with the conventional method. Contrasted to the arduous laborious conventional method, our proposed method offer rapid analysis and simple determination of antioxidant. This proposed LoD method for antioxidant activity in plants would be a platform for the further development of antioxidant assay

Latex micro-balloon pumping in centrifugal microfluidic platforms

Centrifugal microfluidic platforms have emerged as point-of-care diagnostic tools. However, the unidirectional nature of the centrifugal force limits the available space for multi-step processes on a single microfluidic disc. To overcome this limitation, a passive pneumatic pumping method actuated at high rotational speeds has been previously proposed to pump liquid against the centrifugal force. In this paper, a novel micro-balloon pumping method that relies on elastic energy stored in a latex membrane is introduced. It operates at low rotational speeds and pumps a larger volume of liquid towards the centre of the disc. Two different micro-balloon pumping mechanisms have been designed to study the pump performance at a range of rotational frequencies from 0 to 1500 rpm. The behaviour of the micro-balloon pump on the centrifugal microfluidic platforms has been theoretically analysed and compared with the experimental data. The experimental data show that the developed pumping method dramatically decreases the required rotational speed to pump liquid compared to the previously developed pneumatic pumping methods. It also shows that within a range of rotational speed, a desirable volume of liquid can be stored and pumped by adjusting the size of the micro-balloon

Biosensing enhancement of dengue virus using microballoon mixers on centrifugal microfluidic platforms

Dengue is the current leading cause of death among children in several Latin American and Asian countries. Due to poverty in areas where the disease is prevalent and the high cost of conventional diagnostic systems, low cost devices are needed to reduce the burden caused by dengue infection. Centrifugal microfluidic platforms are an alternative solution to reduce costs and increase the availability of a rapid diagnostic system. The rate of chemical reactions in such devices often depends on the efficiency of the mixing techniques employed in their microfluidic networks. This paper introduces a micromixer that operates by the expansion and contraction of a microballoon to produce a consistent periodical 3D reciprocating flow. We established that microballoons reduced mixing time of 12 mu l liquids from 170 min, for diffusional mixing, to less than 23 s. We have also tested the effect of the microballoon mixers on the detection of the dengue virus. The results indicate that employing a microballoon mixer enhances the detection sensitivity of the dengue virus by nearly one order of magnitude compared to the conventional ELISA method. (C) 2014 Elsevier B.V. All rights reserved

Latex micro-balloon pumping in centrifugal microfluidic platforms

Centrifugal microfluidic platforms have emerged as point-of-care diagnostic tools. However, the unidirectional nature of the centrifugal force limits the available space for multi-stepped processes on a single microfluidics disc. To overcome this limitation, a passive pneumatic pumping method actuated at high rotational speeds has been previously proposed to pump liquid against the centrifugal force. In this paper, a novel micro-balloon pumping method that relies on elastic energy stored in a latex membrane is introduced. It operates at low rotational speeds and pumps a larger volume of liquid towards the centre of the disc. Two different micro-balloon pumping designs have been developed to study the pump performance and capacity at a range of rotational frequencies from 0 to 1500 rpm. The behaviour of the micro-balloon pump on the centrifugal microfluidic platforms has been theoretically analysed and compared with the experimental data. The experimental data shows that, the developed pumping method dramatically decreases the required rotational speed to pump liquid compared to the previously developed pneumatic pumping methods. It also shows that within a range of rotational speed, desirable volume of liquid can be stored and pumped by adjusting the size of the micro-balloon