Liquid crystals based sensing platform-technological aspects Zakir Hussain n , Farah Qazi, Muhammad Imran Ahmed, Adil Usman, Asim Riaz, Amna Didar Abbasi School of Chemical and Materials Engineering (SCME), National University of Sciences & Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan article info Article history: Received 13 January 2016 Received in revised form 20 April 2016 Accepted 21 April 2016 Available online 28 April 2016 Keywords: Liquid crystals Biomolecular assemblies Biosensors Detection Toxic chemicals abstract In bulk phase, liquid crystalline molecules are organized due to non-covalent interactions and due to delicate nature of the present forces; this organization can easily be disrupted by any small external stimuli. This delicate nature of force balance in liquid crystals organization forms the basis of Liquid- crystals based sensing scheme which has been exploited by many researchers for the optical visualiza- tion and sensing of many biological interactions as well as detection of number of analytes. In this review, we present not only an overview of the state of the art in liquid crystals based sensing scheme but also highlight its limitations. The approaches described below revolve around possibilities and limitations of key components of such sensing platform including bottom substrates, alignments layers, nature and type of liquid crystals, sensing compartments, various interfaces etc. This review also highlights potential materials to not only improve performance of the sensing scheme but also to bridge the gap between science and technology of liquid crystals based sensing scheme. & 2016 Elsevier B.V. All rights reserved. Contents 1. Introduction ........................................................................................................ 110 2. Key components of LCs based sensing platform ........................................................................... 112 2.1. Substrates.................................................................................................... 112 2.2. Alignment layers .............................................................................................. 114 2.3. Sensor chambers .............................................................................................. 115 2.4. Liquid crystals – signal amplifier ................................................................................. 115 2.5. Assembly of molecules at liquid-air interface ....................................................................... 116 3. Detections visualized in LC-based sensing platform ........................................................................ 117 3.1. Detection of biocatalysts (enzymes) ................................................................................ 117 3.2. Detection of glucose ........................................................................................... 118 3.3. Detection of bio-macromolecules ................................................................................. 119 3.4. Detection of microorganisms .................................................................................... 122 3.5. Detection of heavy metals and volatile organic compounds ............................................................ 123 4. Current gap between science and technology of LCs Based sensing platform .................................................... 125 5. Conclusions ........................................................................................................ 126 Acknowledgement....................................................................................................... 126 References ............................................................................................................. 126 1. Introduction Liquid crystals (LCs) are anisotropic materials having liquid like flow properties as well as solid like optical properties. Such ma- terials show various phases called mesophases which differ from each other due to different orientations of individual molecules with Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/bios Biosensors and Bioelectronics http://dx.doi.org/10.1016/j.bios.2016.04.069 0956-5663/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: zakir.hussain@scme.nust.edu.pk (Z. Hussain). Biosensors and Bioelectronics 85 (2016) 110–127