This paper reports on a microfluidic platform to isolate and study avian red blood cells (RBCs) infected to various degrees by the malaria parasite Plasmodium gallinaceum. The experimental findings point to the feasibility of using the morphological changes on the surface of the malaria infected avian RBC (miaRBCs) as biomarkers for diagnosis. A glass substrate with a controlled surface roughness was used as part of a polydimethylsiloxane (PDMS) microfluidic channels. When whole-blood samples were introduced into the channels, the miaRBCs would be preferentially slowed and eventually become immobilized on the roughened surface. The surface lesions and furrow-like structures on the miaRBC surfaces offered a markedly higher probability to interact with the roughened substrate and allowed the cells to become imobilized on the surface. The captured miaRBCs were from blood samples at various degrees of infection at 3.2%, 3.9%, 9.1%, 13.4%, 20.1%, 28%, and 37%. It was observed that the miaRBCs could be selectively captured under a wall shear rate between 2.1 to 3.2 s−1, which was directly proportional to the flow rate through the channels. This capture rate could be improved by increasing the channel length and finer flow control. It was also found that a roughened glass substrate with ten-point-height larger than the depth of surface lesions and furrow-like structures of miaRBCs showed a substantial enhancement on the number of immobilized infected RBCs. These findings indicated that surface morphologies, including surface lesions and furrow-like structures, can serve as an alternative biomarker for malaria diagnosis.

This article reports a perfusion-based microbioreactor that can be integrated with a thin-film piezoelectric transducer array for rapid disease diagnosis, such as identifications of cancer cells and infection induced cell abnormality. By using the gap between suspended transducers as the high-aspect ratio barriers to establish high flow resistance into the culture chamber, we have verified that diffusion dominated the main transport mechanisms in the culture chamber. The fluid flow was successfully suppressed under 0.03, 0.3, and 3.0 μl/min volume flow rates, and a very low shear flow region was achieved on the transducer surfaces. This design offers minimal influences of mechanical forces on cellular detection and cells cultured on the surface of transducers. Finite element simulation showed that the shear stress on transducer surface could be maintained lower than milli-Pascal range. Detailed design, simulation results and experimental verifications of the microbioreactor are discussed.

This paper demonstrates the substrate dependency of the c-axis zinc oxide growth in radio-frequency sputtering system. Different deposition conditions were designed to study the influences of Si, SiO2/Si, Au/Ti/Si, and Au/Ti/SiO2/Si substrates on the piezoelectric and crystalline qualities of the ZnO thin films. Experimental results showed that the multilayer of Au/Ti/SiO2/Si-coated silicon substrate provided a surface that facilitated the growth of ZnO thin film with the most preferred crystalline orientation. The 1.5 μm-thick thermally grown amorphous silicon dioxide layer effectively masked the crystalline surface of the silicon substrate, thus allowing the depositions of high-quality 20 nm-thick titanium adhesion layer followed by 150 nm-thick of gold thin film. The gold-coated surface allowed deposition of highly columnar ZnO polycrystalline structures. It was also demonstrated that by lowering the deposition rate at the start of sputtering by lowering RF power to less than one-third of the targeted RF power, a fine ZnO seed layer could be created for subsequent higher-rate deposition. This two-step deposition method resulted in substantially enhanced ZnO film quality compared to single-step approach. The influence of stress relaxation by annealing was also investigated and was found to be effective in releasing most of the residual stress in this layered structure.

In this article we demonstrate the effect of mechanical compression on the behavior of cultured neural stem cells using a microelectromechanical system platform. Polydimethylsiloxane (PDMS)-based stretchable substrates were used on a neurosphere (NS) assay to investigate the role of mechanical forces on the formation of radial glial processes and neuronal migration. To induce mechanical compression on NS, the PDMS culturing substrate was patterned with micron-sized wells. NS were cultured on the prestretched device. After 48 hours, when the NS had grown to the size of the well's width, the stretched substrate was released. The experimental results showed that applied mechanical compression on neural stem cells could be a factor accelerating the radial glial formation, which is associated with neurogenesis and neuronal migration.From the Clinical EditorThis study demonstrates that mechanical compression on neural stem cells could be a factor accelerating the radial glial formation, which is associated with neurogenesis and neuronal migration.Polydimethylsiloxane (PDMS)-based stretchable platforms were used on neurosphere (NS) assay to investigate the role of mechanical forces on the formation of radial glial processes and neuronal migration. To induce mechanical compression on NS, the PDMS culturing substrate was patterned with micron-sized wells. NS were cultured on the prestretched device. After 48 hours, when the NS had grown to the size of the well’s width, the stretched substrate was released. The experimental results showed that applied mechanical compression on neural stem cells could be a factor accelerating the radial glial formation, which is associated with neurogenesis and neuronal migration.Download high-res image (219KB)Download full-size image