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Dynamic photonic structures can be tuned by changing the periodic structure and/or the index of refraction. [ 1 ] These dynamic photonic structures allow optically responsive capability to control the properties of light and act as optical transducers to sense external stimuli. [ 2 ] Tunable optical systems operating in the visible and near-infrared region offer great promise for designing adaptive optical materials, telecommunication devices and sensors. Such sensors have been prepared by various methods, including microfabrication, self-assembly or a combination of both. [ 3 ] However, achieving the attributes of a narrow-band response with a high-tunability range to construct off-axis optical sensors still remains a signifi cant challenge.We recently developed an optical sensing platform [ 4 ] based on Denisyuk refl ection holography [ 5 ] and in situ size reduction of metallic nanoparticles in polymers through laser ablation, where an intense laser pulse produces Bragg gratings in a fraction of the time, cost and complexity compared to silver-halide chemistry-based fabrication techniques. [ 6 ] This technique allows the fabrication of holographic sensors that display improved versatility and scalability. The platform utilizes an effi cient approach to produce off-axis chemical-stimuli responsive holographic sensors with a large, reversible narrow-band tunability, using metallic nanoparticles that can be organized in densityconcentrated 3D regions.The present work employs a hologram fabricated by laser ablation comprising of a functionalized hydrophilic host polymer. The optical characteristics of the system were investigated by analyzing the distribution of the mean diameter of Ag 0 nanoparticles, effective refractive indices of ablated and non-ablated polymer-nanoparticle regions, along with angular-resolved measurements. Furthermore, the system was characterized through computational modeling and diffraction simulations. The putative clinical utility of the sensor for the quantifi cation of pH was demonstrated with large wavelength shifts in the entire visible spectrum.Our sensor employs a simultaneous lateral and vertical periodic diffraction grating of silver nanoparticles dispersed within a poly (hydroxyethyl methacrylate)-based (pHEMA) matrix with a dry thickness of approximately 10 µm. The diffracted light is spectrally concentrated at a specifi c narrowband color due to the vertically-ordered periodicity. We use 6 ns-pulsed laser (λ = 532 nm, 240 mJ) standing waves to order the density of silver nanoparticles (mean diameter of 13 ± 9 nm) into regions with a periodicity of approximately half of the wavelength distributed throughout the cross section of the polymer matrix (see Supporting Information). The fabrication of the holographic sensors begins with UV-initiated free radical polymerization of the pHEMA-based hydrogel on an O 2 -plasma-treated poly (methyl methacrylate) (PMMA) substrate ( Figure 1 (a)). Subsequently, Ag + ions are perfused into the pHEMA polymer matrix (Figure 1 (b)), and reduc...

Developing noninvasive and accurate diagnostics that are easily manufactured, robust, and reusable will provide monitoring of high-risk individuals in any clinical or point-of-care environment. We have developed a clinically relevant optical glucose nanosensor that can be reused at least 400 times without a compromise in accuracy. The use of a single 6 ns laser (λ = 532 nm, 200 mJ) pulse rapidly produced off-axis Bragg diffraction gratings consisting of ordered silver nanoparticles embedded within a phenylboronic acid-functionalized hydrogel. This sensor exhibited reversible large wavelength shifts and diffracted the spectrum of narrow-band light over the wavelength range λpeak ≈ 510-1100 nm. The experimental sensitivity of the sensor permits diagnosis of glucosuria in the urine samples of diabetic patients with an improved performance compared to commercial high-throughput urinalysis devices. The sensor response was achieved within 5 min, reset to baseline in ∼10 s. It is anticipated that this sensing platform will have implications for the development of reusable, equipment-free colorimetric point-of-care diagnostic devices for diabetes screening.

The rapidly expanding number of mobile medical applications have the potential to transform the patient-healthcare provider relationship by improving the turnaround time and reducing costs. In September 2013, the U.S. Food and Drug Administration (FDA) issued guidance to regulate these applications and protect consumers by minimising the risks associated with their unintended use. This guidance distinguishes between the subset of mobile medical apps which may be subject to regulation and those that are not. The marketing claims of the application determine the intent. Areas of concern include compliance with regular updates of the operating systems and of the mobile medical apps themselves. In this article, we explain the essence of this FDA guidance by providing examples and evaluating the impact on academia, industry and other key stakeholders, such as patients and clinicians. Our assessment indicates that awareness and incorporation of the guidelines into product development can hasten the commercialisation and market entry process. Furthermore, potential obstacles have been discussed and directions for future development suggested.