Digital printing of selective and reversible ion optodes on fabrics: toward smart clothes for epidermal chemical sensing

While wearable chemical sensors often rely on electrochemical techniques, optical chemical sensors coupled with a smartphone or a miniaturized camera represent an attractive avenue to monitor sweat compositions. In this...

Zeolite-Based Optical Detectors

The detection of chemical species is a common and required task in several areas of technology. Currently, measurements in dedicated labs are the predominant tools for detection and characterization of chemicals and materials. Although these techniques are available in specialized equipment, their use is often bounded by cost of application or the operator's expertise. Also, in many applications rather than an analysis of all the detectable chemical species, it is only of interest to determine the presence of a particular chemical compound, and if it is present, to quantify its concentration. For these reasons, alternative methods for detecting specific chemical species are required. One case of such methods are the optical chemical sensors, particularly the ones based on the materials known as zeolites. In a broad sense, these sensors are constituted by an optical detector that is modified with zeolites. This combination allows the detection of specific chemical compounds if the zeolitic materials is properly modified to have an optical response for the analyte.

Wireless and mobile optical chemical sensors and biosensors

This review explores the current state-of-the-art wireless and mobile optical chemical sensors and biosensors. The review is organised into three sections, each of which investigates a major class of wireless and/or mobile optical chemical sensor: (i) optical sensors integrated with a radio transmitter/transceiver, (ii) wearable optical sensors, and (iii) smartphone camera-based sensors. In each section, the specific challenges and trade-offs surrounding the (bio)chemical sensing mechanism and material architecture, miniaturisation, integration, power requirements, readout, and sensitivity are explored with detailed examples of sensor systems from the literature. The analysis of 77 original research articles published between 2007 and 2017 reveals that healthcare and medicine, environmental monitoring, food quality, and sport and fitness are the target markets for wireless and mobile optical chemical sensor systems. In particular, the current trend for personal fitness tracking is driving research into novel colourimetric wearable sensors with smartphone readout. We conclude that despite the challenges, mobile and wearable optical chemical sensor systems are set to play a major role in the sensor Internet of Things.

Commercial Polycarbonate Track-Etched Membranes as Optical Chemical Sensors

Refractive index is the main parameter measured by current optical sensors. Among all the photonic structures available for their design, porous materials have become an excellent option, since they provide better sensitivities. In our work, commercially available polycarbonate track-etched membranes were used as porous photonic structures. By means of reflectivity measurements, we demonstrated their capability to detect the presence of ethanol in the medium and showed the possibility of reusing them in several sensing assays. This new material could become an easier-to-obtain and cheaper alternative to current porous materials commonly used in optical sensors for refractive index sensing.

Integration and application of optical chemical sensors in microbioreactors

This tutorial review explains the integration of optical chemical sensor formats for the purpose of monitoring oxygen, pH, carbon dioxide, glucose and temperature in microbioreactors.