In this study an optical cellulose fiber for water sensoring was prepared by using a sequential preparation strategy. The core of the fiber was prepared from dissolved cellulose, in [EMIM]OAc, which was dry–wet spun into water. The cladding layer on the cellulose core was produced by coating a layer of cellulose acetate, dissolved in acetone, using a filament coater. The chemical and optical properties of both regenerated cellulose and cellulose acetate were studied from cast films using ultraviolet–visible and Fourier-transform infrared spectroscopy measurements. Regenerated cellulose film was observed to absorb UV light, passing the visible light wavelengths. Cellulose acetate film was observed to pass the whole light wavelength range. The mechanical strength and topography of the prepared optical cellulose fiber were investigated through tensile testing and SEM imaging. The mechanical performance of the fiber was similar to previously reported values in the literature (tensile strength of 120 MPa). The prepared optical fiber guided light in the range of 500–1400 nm. The attenuation constant of the cellulose fiber was observed to be 6.3 dB/cm at 1300 nm. The use of prepared optical cellulose fiber in a water sensor application was demonstrated. When the fiber was placed in water, a clear attenuation in the light intensity was observed. The studied optical fiber could be used in sensor applications, in which easy modifiability and high thermal resistance are beneficial characteristics. Graphic abstract Coaxial cellulose acetate-regenerated cellulose fiber for transporting light in sensor optical fiber sensor applications.

We present a high-throughput roll-to-roll (R2R) manufacturing process for foil-based polymethyl methacrylate (PMMA) chips of excellent optical quality. These disposable, R2R hot embossed microfluidic chips are used for the identification of the antibiotic resistance gene mecA in Staphylococcus epidermidis. R2R hot embossing is an emerging manufacturing technology for polymer microfluidic devices. It is based on continuous feeding of a thermoplastic foil through a pressurized area between a heated embossing cylinder and a blank counter cylinder. Although mass fabrication of foil-based microfluidic chips and their use for biological applications were foreseen already some years ago, no such studies have been published previously.

Flexible optoelectronic technologies are becoming increasingly important with the advent of concepts such as smart-built environments and wearable systems, where they have found applications in displays, sensing, healthcare, and energy harvesting. Parallelly, there is also a need to make these innovations environmentally sustainable by design. In the present work, we employ nanocellulose and its excellent film-forming properties as a basis to develop a green flexible photonic device for sensing applications. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) were used as matrix materials along with a black thermochromic pigment to prepare thermoresponsive hybrid films. Optical properties of nanocellulose films such as transparency and haze were tuned by varying pigment loading. Nearly 90% transparent CNF and CNC films could be tuned to reduce the transmission to as low as 4 and 17%, respectively. However, the films regained transparency to up to 60% when heated above the thermochromic transition temperature (31 °C). The thermoresponsive behavior of the prepared films was exploited to demonstrate an all-optical modulation device. Continuous infrared light (1300 nm) was modulated by using a 660 nm visible diode laser. The laser intensity was sufficient to cause a localized thermochromic transition in the films. The laser was pulsed at 0.3 Hz and a uniform cyclic modulation depth of 0.3 dB was achieved. The demonstrated application of functional nanocellulose hybrid films as a light switch (modulator) could be harnessed in various thermally stimulated sensing systems such as temperature monitoring, energy-saving, and anti-counterfeiting.