Abstract— The possibility of miniaturization of existing optical setups and technologies for the monitoring and control in microfluidics could represent a step toward the realization of a complete polymeric micro-optic-fluidic system. In this context the presented work involves the design and the optic simulation of PDMS micro-optic interfaces to reproduce the microfluidic feedback: a bubble flow to control a bubble flow. I. INTRODUCTION UGE advances have been made in silicon-based technology over the last few decades and different strategies of integration of microfluidics with electronics have been widely explored and exploited [1]-[2]-[3]. Such technology therefore no longer represents a mysterious tool for the realization of chemical, temperature [4] and optical- sensors [5]. Silicon-based advances have also been made in the realization of a wide range of electro-mechanical sensors and actuators using micro-electro-mechanical systems (MEMS) [6]. At the same time, the use of polymers, such as PDMS (Poly-dimethylsiloxane) and PMMA (poly-methyl methacrylate), to develop sensing and actuation in microfluidics, is raising interest [7]-[8]. Several studies [9] in literature show how they can be sensitive to pressure, light, temperature, or chemicals leading to the idea of polymeric sensors. In addition in the case of polymeric smart materials [10]-[11] their electro-mechanical properties can be modified and tuned by applying voltage yield to polymeric actuators. Among these potentialities, they also present an evolution toward the miniaturization of the optical setup based on bulky microscopy. Polymeric micro-optic interface can be designed exploiting their optical properties and their integration with fiber optics and standard optical detectors. Integration of components and interfacing of devices with the user is convenient and simpler in PDMS than in systems made hard materials [12]. For all these reasons this technology could represent a step forward in solving issues related to the development of microfluidic chip interfaces for the monitoring and control of bubble/droplet flow. Ad hoc designed polymeric micro-optic devices, would allows the creation of completely polymeric integrated chip, respecting the spatial and temporal resolution of the Manuscript sumitted March 11, 2011 F.Sapuppo, P.Anandan, M. Bucolo Dipartimento di Ingegneria Elettrica Elettronica ed Informatica, Universita’ degli studi di Catania maide.bucolo@dieei.unict.it phenomena under investigation and fulfilling the requirement of non-invasiveness and bio-compatibility. Their design representing a miniaturization and optimization of standard optical setup designs, would provide the opportunity for a continuous monitoring and actuation of the flow processes independently of the experimental setup and disturbances in portable and disposable Lab on Chip system (LOC). In this context, the presented work involves the design and the optic simulation of PDMS micro-optic interfaces that allow establishing the microfluidic feedback: a bubble flow to control a bubble flow. The final aim is to realize a self-contained device in which a microfluidic process under study is controlled through a second microfluidic process which implements specific bubble logic. Optical actuation and sensing are exploited and, therefore, no use of electronics neither for control, nor for sensing is required. The novelty of such design is, in fact, to foresee the integration through PDMS technology of micro-optics [13], laser light actuation [14]-[15], bubble/droplet logic [16]. In this paper, the physics and technological aspect involved in the design of a micro-opto-fluidic system are reported in Section II. Beside, Section III presents the design of the PDMS micro-opto-fluidic device and the ray tracing simulations for the integration of the laser actuation and the bubble flow optical detection with the microfluidic processes. II. PHYSICAL AND TECHNOLOGICAL BACKGROUND A. Macro Optics to Micro Optics Polymeric miniaturized devices based on multilayer PDMS technology have good optical properties, transparency and biological compatibility. Recently it has been proved their versatility to realize device for flow monitoring, being a valid alternative to microscopy and other integrated velocimetry optical methods [17]-[18]. PDMS can be used to realize optic components as wave guides [19], micro-lenses [20], and micro-mirrors [21]. The principle of the PDMS wave guides is based on the PDMS/air interface and their difference in refraction index (RI) (n air =1, n PDMS =1.41) that allows generating total internal reflection (TIR) for confining the light rays into PDMS guides surrounded by air. The principle of the PDMS micro-lenses can be described as follows: curved air/PDMS interfaces cause the incident light beams to be deflected, and focused according to the Micro-Optic Technology for the Microfluidics Feedback F. Sapuppo Member, IEEE, P. Anandan, M. Bucolo, Senior, IEEE H 2011 IEEE International Conference on Automation Science and Engineering Trieste, Italy - August 24-27, 2011 ThC4.2 978-1-4577-1732-1/11/$26.00 ©2011 IEEE 381