Showing papers by "Richard B.M. Schasfoort published in 2004"
TL;DR: Application of colloidal gold led to a sensitivity increase of approximately three orders of magnitude compared with nonamplified detection and the corresponding LOD was approximately 0.15 ng PSA/ml, which is sufficient for measuring enhanced, clinically relevant PSA levels (>4 ng/ml).
105 citations
TL;DR: The results presented show that address‐flow microfluidics allow easy and accurate control of sample stream position and width, and is a new unit operation that might aid in separation and collection inmicrofluidic devices.
Abstract: The so-called address-flow principle is described: a valveless, electroosmotically driven technology used for controlling the stream profile in a laminar flow chamber. The method is explained, and a theoretical description and experimental verification are presented. Adjustment of the flow of two electroosmotically controlled guiding streams, running parallel to a central sample stream, can be used for positioning the sample stream in the dimension perpendicular to the flow direction. The results presented show that address-flow microfluidics allow easy and accurate control of sample stream position and width. The electroosmotic flow (EOF)-controlled guiding of microfluidic flows described in this paper, is a new unit operation that might aid in separation and collection in microfluidic devices. One possible application of addressflow microfluidics is guiding of capillary electrophoresis-separated components over a multisensor array, in order to perform affinity assays.
16 citations
TL;DR: A microfluidic device capable of recirculating nanoliter volumes in restricted microchannel segments, reversibly sealed to a glass substrate with integrated platinum electrodes, and small analyte volumes can be mixed for prolonged times within well-defined channel segments and/or exposed to in-channel sensor surfaces.
Abstract: A microfluidic device is described, capable of recirculating nanoliter volumes in restricted microchannel segments The device consists of a PDMS microfluidic structure, reversibly sealed to a glass substrate with integrated platinum electrodes The integrated electrodes generate electroosmotic flow locally, which results in a cycling flow in the channel segment between the two electrodes in case one channel exit is closed (dead-end channel) This cycling flow is a consequence of the counterbalancing hydrodynamic pressure against the electroosmotically generated flow Acid−base indicators were employed to study the formation of H+ and OH- at both the in-channel electrodes The formation of acid can locally change the zeta-potential of the channel wall, which will affect the flow profile Using this method, small analyte volumes can be mixed for prolonged times within well-defined channel segments and/or exposed to in-channel sensor surfaces
12 citations
TL;DR: In this article, a microfluidic structure based on the electroosmotic guiding of reagent streams is presented that can be used as a fully adjustable diffusion based microreactor.
Abstract: A novel microfluidic structure based on the electroosmotic guiding of reagent streams is presented that can be used as a fully adjustable diffusion based microreactor. The position and the width of two aqueous reactant streams entering a laminar-flow chamber can be controlled individually by changing the flow ratio of three parallel guiding streams containing buffer only. To control the intensity of product formation, the overlapping area between the diffusion regions of the two different reagent streams can be adjusted. This article describes the fabrication and experimental characterization of the device.