Microparticle photometry in a CMOS microsystem combining magnetic actuation and in situ optical detection

We present a hybrid CMOS-based microfluidic system that combines magnetic actuation of microparticles with in situ optical detection using ingle photon avalanche diodes (SPADs). The decoupling of the principles used for actuation and sensing permits a high sensitivity with respect to etection and particle handling. Single magnetic microparticles are transported within a glass micro-capillary positioned over an array of actuation oils and are detected upon passage over a SPAD, where they block incident light and thus lower the photon count. Use of the photometry method llows the determination of the particle size, which, in combination with a simultaneous measurement of the particle velocity, enables us to estimate urther particle properties, such as their magnetization. We present the successful manipulation, detection and evaluation of magnetic particles with iameters ranging from 1 to 30 m. 2007 Elsevier B.V. All rights reserved.