Biosensors & Bioelectronics 15 (2000) 417 – 421 Short communication A liquid crystal pixel array for signal discrimination in array biosensors Jeffrey S. Lundgren, A. Neal Watkins, David Racz, Frances S. Ligler * Naal Research Laboratory, Center for Biomolecular Science and Engineering, Code 6900, Washington, DC 20375 -5348, USA Received 23 July 1999; accepted 28 March 2000 Abstract A new optical design uses a liquid crystal pixel array (LCPA) to discriminate multiple fluorescence signals on a two-dimensional biosensor array. The LCPA can selectively control the transmission of fluorescence generated from multiple biosensing elements on a planar waveguide. This device sequentially acquires the fluorescence data from the substrate by making multiple individual measurements of the sensing elements on the waveguide. The biosensing elements are patterned according to the pixel layout of the LCPA and optically aligned so that each electronically driven pixel can either transmit or filter out the fluorescence signal as specified by the user. The primary advantage of this system is that a single detection channel (i.e. photomultiplier tube (PMT)) can be used to measure multiple fluorescence signals from a two-dimensional substrate while the LCPA provides for spatial resolution. We evaluate the performance of the LCPA by testing the optical homogeneity of the liquid crystal pixels and linear dynamic range for transmitting light. The LCPA is also used with well-developed biosensing chemistry modified for this optical format. Published by Elsevier Science S.A. Keywords: Biosensor; Liquid crystal array; Multi-analyte sensing www.elsevier.com/locate/bios 1. Introduction Multi-analyte biosensing assays that an operator can perform rapidly on a small, disposable platform with- out prerequisite knowledge of the sensing chemistry are in demand (Harrison et al. 1998). Through immobiliz- ing highly-selective biornolecules onto the sensor sub- strate and developing a mode for signal transduction, one can obtain quantitative and/or qualitative chemical information pertaining to the sample. Biosensors have demonstrated their potential for use in pharmaceutical science, food processing, environmental science, detec- tion of biowarfare agents, and home medical diagnos- tics. In order to make it to the commercial sector, biosensors must be able to provide a significant advan- tage(s) over conventional analytical methods. The ideal biosensor is relatively compact, durable, light-weight, and battery powered. Additionally, biosensors should be cost-effective; meaning that the disposable compo- nents, system hardware, and operating costs all need to be competitive with those of other methods. One solution to the cost constraints placed on biosensor designs/systems is an array-based format (Wadkins et al., 1997; Feldstein et al., 1998; Sangodkar et al., 1996). By incorporating multiple biosensing ele- ments onto a single biosensing platform, a number of costs associated with sample analysis can be reduced while still yielding a large number of chemical answers. Array-based biosensing has been proposed for many different chemical systems and applications, as well as through a variety of instrumental approaches (Johnson et al., 1997; Michael et al., 1998; Vo-Dinh et al., 1999; Isolana, et al., 1998). Microfabrication techniques with electronics, machining, and chemical patterning have made sensing chips smaller, more affordable, and more practical for routine use. * Corresponding author. E-mail address: fligler@cbmse.nrl.navy.mil (F.S. Ligler). 0956-5663/00/$ - see front matter Published by Elsevier Science S.A. PII:S0956-5663(00)00098-1