Phaseguide-assisted blood separation microfluidic device for point-of-care applications

We propose a blood separation microfluidic device suitable for point-of-care (POC) applications. By utilizing the high gas permeability of polydimethylsiloxane (PDMS) and phaseguide structures, a simple blood separation device is presented. The device consists of two main parts. A separation chamber with the phaseguide structures, where a sample inlet, a tape-sealed outlet, and a dead-end ring channel are connected, and pneumatic chambers, in which manually operating syringes are plugged. The separation chamber and pneumatic chambers are isolated by a thin PDMS wall. By manually pulling out the plunger of the syringe, a negative pressure is instantaneously generated inside the pneumatic chamber. Due to the gas diffusion from the separation chamber to the neighboring pneumatic chamber through the thin permeable PDMS wall, low pressure can be generated, and then the whole blood at the sample inlets starts to be drawn into the separation chamber and separated through the phaseguide structures. Reversely, after removing the tape at the outlet and manually pushing in the plunger of the syringe, a positive pressure will be created which will cause the air to diffuse back into the ring channel, and therefore allow the separated plasma to be recovered at the outlet on demand. In this paper, we focused on the study of the plasma separation and associated design parameters, such as the PDMS wall thickness, the air permeable overlap area between the separation and pneumatic chambers, and the geometry of the phaseguides. The device required only 2 μl of whole blood but yielding approximately 0.38 μl of separated plasma within 12 min. Without any of the requirements of sophisticated equipment or dilution techniques, we can not only separate the plasma from the whole blood for on-chip analysis but also can push out only the separated plasma to the outlet for off-chip analysis.     

Professor Terence McLaughlin 1949–2006

Terry McLaughlin's death earlier this year came as a devastating shock to all his many friends. He will be remembered by all as a gifted scholar whose lifelong commitment to education was etched in his every thought, word and deed. The list of his achievements in the educational world is a long, honourable and deeply distinguished one, including a notable period of editorial duty on CJE from 1992 to 2003. Terry will be remembered with profound affection and respect by all those who were fortunate enough to know him. For each one of us, his memory will forever be a joy, and his example an enduring inspiration. The following lines are extracted from the address given at his memorial service at St Edmund's College, Cambridge on 11 April 2006.     

Moving beyond the metaphor of transfer of learning

This paper argues that much contemporary educational policy makes assumptions about learning that are directly contradicted by the best research and theorising of learning that has occurred over the last decade and more. This worrying mismatch is largely attributable to adherence by policy makers (and other key stakeholders such as employers), to ‘common sense’ notions of learning transfer. In fact, these ‘common sense’ notions of transfer have increasingly been discarded even in the learning transfer literature. However, we go further in arguing that transfer is a totally inappropriate metaphor for thinking about most learning, but especially for vocational learning. Accepting that thought about learning inevitably involves metaphors, we consider the merits and otherwise of various other learning metaphors including participation and construction. We conclude that the conceptual flaws of transfer can be avoided by employing alternative metaphors. The value of our recommended alternative is illustrated by its power to illuminate data on learning collected from various research projects.