Soft Fibers Research Articles

Fiber optical parametric oscillator made of soft glass

Fiber optical parametric oscillators (FOPOs) are compact optical sources of coherent and broadly tunable light compatible with operation in unconventional spectral bands. Highly nonlinear silica fibers have enabled the development of FOPOs in the telecommunication wavelength band, but the strong material absorption of silica glass at wavelengths >2 µm limits its applicability in the mid-infrared (MIR) spectral range. In this work, we overcome this issue and report a FOPO designed entirely out of soft glass fiber. For this purpose, we combine an As2Se3 single-mode fiber coupler, an As2Se3 parametric gain medium, and a low-loss ZBLAN delay fiber to build the first all-fiber laser cavity made of soft glass. Two proof-of-concept FOPOs are presented, one driven by pure parametric gain leading to wavelength-tunable Stokes emission within the range 2.088-2.139 µm, and the other driven by Raman-assisted parametric gain leading to Stokes emission within the range 2.023-2.048 µm. This demonstration is a promising first step toward the development of fully fiberized MIR light sources.

Extraction and Characterization of Fibers from Corn Husk

ABSTRACT In the present research, corn husk fibers were extracted by chemical method using sodium hydroxide followed by acid treatment. The objective was to obtain easily twistable, soft and fine fibers. The extracted fibers were characterized in terms of their physical properties. Thermo-gravimetric analysis was also preformed to assess the effect of acid treatment on the fiber thermal properties. It was found that, alkali treatment yields 26–28% fibers on the weight of husk treated. Acid treatment with Sulfuric acid removes impurities such as hemi-cellulose and lignin and is directly related to acid concentration. Acid treatment reduces fiber length, but however, a milder treatment results in a longer fiber length distribution. The linear density of alkali treated fibers reduces from 61 dtex to 30 dtex after the acid treatment. In addition, acid treatment also results in reduction of moisture regain from 13.5% to 11.75%. The alkali treated fibers show a tenacity value of 16.2 cN/Tex and this value reduces after the acid treatment. Interestingly, the fibers treated with acid at 7.5gpl concentration exhibit a highest value of 18.1 cN/Tex and this value reduces further to 12.5cN/Tex as the acid concentration increases. Acid treatment results in more thermally stable fibers.

Experimental Investigations on the Mechanical and Microscopic Behavior of Cement-Treated Clay Modified by Nano-MgO and Fibers

Cement is often used to stabilize soft clay; however, it has some limitations in increasing clay strength and improving clay failure mode. To solve this, two different additives, i.e., polypropylene fiber and nano-Magnesium Oxide (MgO), were tested with the purpose of improving the mechanical performance of cement-treated soft clay. Four groups of samples with different mixture ratios of coastal soft clay, cement, fiber, and nano-MgO were first designed. Microscopy tests including X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), as well as unconfined compression test was then carried out. XRD and EDS test results show that the cement hydration reaction is the main source of strength increase and the nano-MgO can generate Magnesium Silicate Hydrates (M-S-H) gelation, which helps to fill the pores of the clay and increase clay compactness. The unconfined compressive strength test results show that adding fiber or nano-MgO alone has a poor effect on the strength improvement for cement-treated clay with high water content. However, adding both additives lead to a significant increase in the clay’s unconfined compressive strength, which is verified by the microscopic observation of clay compactness in SEM images. Moreover, the fiber is found to increase the ductility of cement-treated clay based on the observed failure modes of modified samples.

A study on the influence of cross-sectional shapes and convolutions on PVDF fiber properties

Polyvinylidene fluoride (PVDF) is a piezoelectric polymer for the potential massive production of smart textiles, facing the difficulty of synergetic improving its fiber strength and softness. Strengthening of flexible PVDF fibers via drawing incurs the reduction of fiber softness. Here, inspired by the cotton fibers, this study aimed to construct a strong and soft PVDF fiber by regulating its cross-sectional shape and longitudinal convolution. Mechanism of increasing softness by longitudinal spiral twisting was conducted during the strengthening of PVDF fibers with favorable cross-sectional shapes. Then circular, flat and kidney shaped PVDF fibers were prepared to conduct drawing and twisting under different parameters. The influences of cross-sectional shapes and convolutions on PVDF fiber properties were examined using scanning electron microscope (SEM), X ray diffraction (XRD), universal stretch meter and AFM. Results indicated that all the fibers became strong but rigid with increased drawing ratios, mainly due to their corresponding attenuation to increase fiber inner crystallization and surface smoothness. In specialty, the circular fiber had a higher crystallization increase ratio (106.3%) than that of kidney (74.7%) and flat (73.1%) fibers. Surprisingly, all drawn fibers became flexible and further strengthened after tensile twisting within 400 T/m. Overall the optimum strong and flexible fibers were obtained by 400 T/m tensile twisting of the 2 times drawn flat PVDF fibers.

Experimental investigation on high-temperature creep behavior of carbon fiber reinforced polymer cable

Both steady state-constant load and temperature (ST-CLT), and transient state-constant load and temperature (TR-CLT) tests were conducted on carbon fiber reinforced polymer (CFRP) cable in order to investigate the corresponding high-temperature creep behavior. The failure modes, creep strains and rupture times of CFRP cables exposed to high temperature were obtained in ST-CLT and TR-CLT tests, while the residual tensile strength and elastic modulus of specimens without rupture after high-temperature creep tests were determined by conducting high-temperature tensile tests. The variation law of high-temperature creep strains and rupture times of CFRP cable obtained from ST-CLT tests were compared to these of TR-CLT tests to identify the effect of temperature-load path. A practical model for characterizing the high-temperature creep behavior of CFRP cable was developed. Finally, the sustained stress levels and rupture times of specimens exposed to high temperature were analyzed to predict the high-temperature creep rupture stress level of CFRP cable. The obtained results indicated that the rupture morphology of high-temperature creep rupture specimens was the completely soft fiber bundles with “fluffy” pattern. The high-temperature creep strains of CFRP cables in ST-CLT and TR-CLT tests were highly depended on temperature, sustained stress level and time. The presence of pre-tension load before heating accelerated the damage of strength and stiffness for CFRP cable at high temperature, and the damage degree increased with the increasing sustained stress level and high-temperature. The developed practical models for CFRP cables under ST-CLT and TR-CLT conditions can accurately predict the high-temperature creep strains. In the fire resistant design of pre-stressed structures with CFRP cables, the effect of high-temperature creep rupture stress of CFRP cable was not negligible.

Cotton Weaving Waste Incorporation in PVC Composites

The largest amount of solid waste from the textile industries is mainly derived from fabric manufacturing until the cutting stage: hard fibers (spinning waste), beaming and soft fibers (weaving yarn waste), and off-cuts (cutting process). This research aimed to (i) conduct an exploratory interview with a large Brazilian cotton textile manufacturer to identify its main solid waste and corresponding destinations; and (ii) produce and evaluate PVC composites reinforced with cotton textile residues from the weaving process. Cotton fibrous reinforcements in the proportion of 2.5% (w/w) presented the best results of tensile strength and elongation concerning the others. Briquette residue (2.5%) had better dispersion in the matrix and slightly higher tensile strength when compared to other residues. The composites presented different visual aspects, and their use in fashion products with sustainable appeal could be a viable alternative. Therefore, additional tests should be performed to ensure the appropriate mechanical properties for applications in this and other areas.

Split waste from rattan industry? Crafted product and furniture industry fiber bar

This research aims to reduce and use wastes of rattan industries, especially during the splitting stage. This stage refers to the process of making the rattan into rattan fiber strips. This Research & Development experimented with developing the previous study, using NaOH to produce the fibers. The research procedure included preparing, soaking, washing, pressing, drying, tensile, stretching, and workmanship-experimenting processes. The most effective and efficient process, with reliable rattan fiber strips for industrial purposes, was the 1kg soaking process of rattan. 1 Liter of H2O: NaOH 98%, 100gram: 72 hours of the soaking process The result was light-brown, soft, and flexible rattan fiber strips. The widths of the strips were between 20mm and 35mm. The thicknesses of the strips were between 0.5 and 1mm. The length was adjusted based on the initial length of the material, 6000mm. The tensile strength of the rattan fiber was 3.747N while the stretching strength was 6.796%. The implementation of the fibers included crafted product designs and decorative or functional furniture. The applicable craftsmanship techniques included weaving, bundling, and winding. The rattan fiber strips of the research could be the innovation base or applied research result for product design and green interior.

Single-mode tellurite optical fiber for temperature measurement based on the self-phase modulation effect.

In this paper, the self-phase modulation (SPM) effect in a double-cladding single-mode tellurite optical fiber (DC-SMTOF) was exploited for temperature sensing. The DC-SMTOF was fabricated based on a TeO2-ZnO-Li2O-Bi2O3 (TZLB) glass material that has a thermo-optical coefficient as high as -16.4×10-6/°C. The temperature sensing performance was evaluated by detecting the 3-dB bandwidth of the SPM spectra with the variation of temperature at different pump wavelength and different average pump power. The temperature sensitivity was obtained to be -2.971 nm/°C with a resolution of 0.0168°C. Both simulation and experiment confirmed that a longer pump wavelength and higher average pump power will result in a higher temperature sensitivity. To the best of our knowledge, this is the first study concerning SPM-based temperature sensing in a tellurite optical fiber. The proposed temperature sensor has a compact structure, and it can realize temperature sensing of high sensitivity without any fiber modification. This work opens the road toward explorations of a novel temperature sensing technology combined with soft glass fibers and nonlinear phenomenon, and is expected to deepen our understanding in the application of these complex nonlinear phenomena.

Adaptive polymer fiber neural device for drug delivery and enlarged illumination angle for neuromodulation

Objective. Optical fiber devices constitute significant tools for the modulation and interrogation of neuronal circuitry in the mid and deep brain regions. The illuminated brain area during neuromodulation has a direct impact on the spatio-temporal properties of the brain activity and depends solely on the material and geometrical characteristics of the optical fibers. In the present work, we developed two different flexible polymer optical fibers (POFs) with integrated microfluidic channels (MFCs) and an ultra-high numerical aperture (UHNA) for enlarging the illumination angle to achieve efficient neuromodulation. Approach. Three distinct thermoplastic polymers: polysulfone, polycarbonate, and fluorinated ethylene propylene were used to fabricate two step-index UHNA POF neural devices using a scalable thermal drawing process. The POFs were characterized in terms of their illumination map as well as their fluid delivery capability in phantom and adult rat brain slices. Main results. A 100-fold reduced bending stiffness of the proposed fiber devices compared to their commercially available counterparts has been found. The integrated MFCs can controllably deliver dye (trypan blue) on-demand over a wide range of injection rates spanning from 10 nl min−1 to 1000 nl min−1. Compared with commercial silica fibers, the proposed UHNA POFs exhibited an increased illumination area by 17% and 21% under 470 and 650 nm wavelength, respectively. In addition, a fluorescent light recording experiment has been conducted to demonstrate the ability of our UHNA POFs to be used as optical waveguides in fiber photometry. Significance. Our results overcome the current technological limitations of fiber implants that have limited illumination area and we suggest that soft neural fiber devices can be developed using different custom designs for illumination, collection, and photometry applications. We anticipate our work to pave the way towards the development of next-generation functional optical fibers for neuroscience.

Simultaneous Wide-Field Planar Strain-Fiber Orientation Distribution Measurement Using Polarized Spatial Domain Imaging.

In the present study, we demonstrate that soft tissue fiber architectural maps captured using polarized spatial frequency domain imaging (pSFDI) can be utilized as an effective texture source for DIC-based planar surface strain analyses. Experimental planar biaxial mechanical studies were conducted using pericardium as the exemplar tissue, with simultaneous pSFDI measurements taken. From these measurements, the collagen fiber preferred direction [Formula: see text] was determined at the pixel level over the entire strain range using established methods ( https://doi.org/10.1007/s10439-019-02233-0 ). We then utilized these pixel-level [Formula: see text] maps as a texture source to quantify the deformation gradient tensor [Formula: see text] as a function of spatial position [Formula: see text] within the specimen at time t. Results indicted that that the pSFDI approach produced accurate deformation maps, as validated using both physical markers and conventional particle based method derived from the DIC analysis of the same specimens. We then extended the pSFDI technique to extract the fiber orientation distribution [Formula: see text] as a function of [Formula: see text] from the pSFDI intensity signal. This was accomplished by developing a calibration procedure to account for the optical behavior of the constituent fibers for the soft tissue being studied. We then demonstrated that the extracted [Formula: see text] was accurately computed in both the referential (i.e. unloaded) and deformed states. Moreover, we noted that the measured [Formula: see text] agreed well with affine kinematic deformation predictions. We also demonstrated this calibration approach could also be effectively used on electrospun biomaterials, underscoring the general utility of the approach. In a final step, using the ability to simultaneously quantify [Formula: see text] and [Formula: see text], we examined the effect of deformation and collagen structural measurements on the measurement region size. For pericardial tissues, we determined a critical length of [Formula: see text] 8 mm wherein the regional variations sufficiently dissipated. This result has immediate potential in the identification of optimal length scales for meso-scale strain measurement in soft tissues and fibrous biomaterials.

Centrifugal Assembly of Helical Bijel Fibers for pH Responsive Composite Hydrogels.

In microfluidics, centrifugal forces are important for centrifugal microfluidic chips and curved microchannels. Here, an unrecognized use of the centrifugal effect in microfluidics is introduced. The assembly of helical soft matter fibers in a rotating microcapillary is investigated. During assembly, the fibers undergo phase separation, generating particle stabilized bicontinuous interfacially jammed emulsions gels. This process is accompanied by a transition of the fiber density over time. As a result, the direction of the centrifugal force in the rotating microcapillary changes. The authors analyze this effect systematically with high-speed video microscopy and complementary computer simulations. The resulting understanding enables the control of the helical fiber assembly into microropes. These microropes can be converted into pH responsive hydrogels that swell and shrink with potential applications in tissue engineering, soft robotics, controlled release, and sensing. More generally, the knowledge gained from this work shows that centrifugal forces potentially enable directed self-assembly or separation of colloids, biological cells, and emulsions in microfluidics.

Fibrous Scaffolds for Muscle Tissue Engineering Based on Touch-Spun Poly(Ester-Urethane) Elastomer.

Development of fiber-spinning technologies and materials with proper mechanical properties is highly important for the manufacturing of aligned fibrous scaffolds mimicking structure of the muscle tissues. Here, the authors report touch spinning of a thermoplastic poly(1,4-butylene adipate)-based polyurethane elastomer, obtained via solvent-free polymerization. This polymer possesses a combination of important advantages such as 1) low elastic modulus in the range of a few MPa, 2) good recovery ratio and 3) resilience, 4) processability, 5) nontoxicity, 6) biocompatibility, and 7) biodegradability that makes it suitable for fabrication of structures mimicking extracellular matrix of muscle tissue. Touch spinning allows fast and precise deposition of highly aligned micro- and nano-fibers without use of high voltage. C2C12myoblasts readily align along soft polymer fibers and demonstrate high viability as well as proliferation that make proposed combination of polymer and fabrication method highly suitable for engineering skeletal muscles.

Shear-induced migration of confined flexible fibers.

We report an experimental study of the shear-induced migration of flexible fibers in suspensions confined between two parallel plates. Non-Brownian fiber suspensions are imaged in a rheo-microscopy setup, where the top and the bottom plates counter-rotate and create a Couette flow. Initially, the fibers are near the bottom plate due to sedimentation. Under shear, the fibers move with the flow and migrate towards the center plane between the two walls. Statistical properties of the fibers, such as the mean values of the positions, orientations, and end-to-end lengths of the fibers, are used to characterize the behaviors of the fibers. A dimensionless parameter Λeff, which compares the hydrodynamic shear stress and the fiber stiffness, is used to analyze the effective flexibility of the fibers. The observations show that the fibers that are more likely to bend exhibit faster migration. As Λeff increases (softer fibers and stronger shear stresses), the fibers tend to align in the flow direction and the motions of the fibers transition from tumbling and rolling to bending. The bending fibers drift away from the walls to the center plane. Further increasing Λeff leads to more coiled fiber shapes, and the bending is more frequent and with larger magnitudes, which leads to more rapid migration towards the center. Different behaviors of the fibers are quantified with Λeff, and the structures and the dynamics of the fibers are correlated with the migration.

All-fiber biological detection microfluidic chip based on space division and wavelength division multiplexing technologies.

To further reduce the size of a microfluidic detection chip and the sample consumption and to shorten the chip manufacturing cycle, an all-fiber SPR detection multichannel microfluidic chip was proposed and demonstrated in this paper. The microfluidic channel of the proposed chip was provided by the air channel of a double side-hole fiber, the detection unit was fabricated using a dumbbell fiber with a fiber core exposed to air, and the sensing probe was composed and packaged by fiber micro-processing technology. The internal double channels of the fiber constructed from double side-hole and dumbbell fibers can realize dual channel detection based on space division multiplexing. 30 nm silver and 50 nm gold films were respectively coated on the left and right sides of the dumbbell fiber, which can realize the dual channel simultaneous detection based on wavelength division multiplexing. We employed the proposed microfluidic chip to detect immunoglobulin G and dopamine molecules, where the average sensitivity is 0.252 nm (mg mL-1)-1 and 0.061 nm (μg mL-1)-1, and the LOD is 0.397 mg mL-1 and 1.639 μg mL-1, respectively. The microfluidic channel and detection unit of all-fiber multi-channel SPR detection microfluidic chip are provided by a soft and flexible fiber, which is compact in structure, flexible in fabrication and short in manufacturing cycle, making it possible for the microfluidic chip to enter the human body for detection and enabling a new approach for the fabrication of wearable detection microfluidic devices. This provides a new idea for the development of microfluidic chips.

A hyperelastic-damage model to study the anisotropic mechanical behavior of coral-hydrogel bio-composite

In this research, a hyperelastic strain energy function was developed to investigate the anisotropic mechanical behavior of a soft bio-composite containing the coral collagen fibers and alginate hydrogel matrix. This hyperelastic function considers the matrix isotropic response, anisotropic behavior of soft crimpled fibers, and matrix-fiber interaction. The material parameters of the model were assumed as a function of the volume fraction of fibers to consider the fiber content. The published experimental data of matrix and bio-composites with different volume fractions of fibers in different directions were used to find the material parameters. A damage model was developed to take into account the damage of matrix, fibers, and fiber-matrix interaction. Results showed that the interaction contribution increases by increasing the volume fraction of fibers due to the crosslinks between the matrix and fibers. Moreover, by exceeding the fibers volume fraction from 20%, the anisotropic stiffening dominates the interaction stiffening in the longitudinal test owing to the load-bearing of soft fibers. Simulation results exhibited that cross-plied bio-composites show more uniform deformations than angle-plied bio-composites. Moreover, the damage results showed that the matrix plays a significant role in the failure of bio-composites.

Impact-resistant membranes from electrospun fibers with a shear-thickening core

Shear thickening fluid (STF) has great application potentials in the development of soft armors due to their unique properties. In this present study, the coaxial electrospinning method was used for the first time, using STF as the core of the composite fiber and polyketone (PK) as the sheath to fabricate a soft, foldable and impact-resistant fiber membrane with a mesh structure. The morphology, structure, chemical components, and impact resistance of the fiber membrane were characterized in detail. A core/shell structure was observed in the fiber cross section clearly. The impact resistance of the composite fibers (core to sheath ratio = 1:4, STF content = 46.2%), was about 33.3% higher than that of pure PK fibers without a core. When only one layer of the composite fibers (areal density = 60 g/m2) was added as an interlayer to two layers of aramid 1414 fibers, the impact resistance of the fabric increased by 18.8%. When spray coating resin was used in combination with only one layer of the composite fibers (areal density = 60 g/m2), the impact resistance of the fabric was enhanced by 27.8%. Therefore, the resultant fiber membrane has broad application prospects as an impact protection material.

Soft fibers with magnetoelasticity for wearable electronics

Magnetoelastic effect characterizes the change of materials’ magnetic properties under mechanical deformation, which is conventionally observed in some rigid metals or metal alloys. Here we show magnetoelastic effect can also exist in 1D soft fibers with stronger magnetomechanical coupling than that in traditional rigid counterparts. This effect is explained by a wavy chain model based on the magnetic dipole-dipole interaction and demagnetizing factor. To facilitate practical applications, we further invented a textile magnetoelastic generator (MEG), weaving the 1D soft fibers with conductive yarns to couple the observed magnetoelastic effect with magnetic induction, which paves a new way for biomechanical-to-electrical energy conversion with short-circuit current density of 0.63 mA cm−2, internal impedance of 180 Ω, and intrinsic waterproofness. Textile MEG was demonstrated to convert the arterial pulse into electrical signals with a low detection limit of 0.05 kPa, even with heavy perspiration or in underwater situations without encapsulations.

Sensitivity of the shear wave speed-stress relationship to soft tissue material properties and fiber alignment

The use of shear wave propagation to noninvasively measure material properties and loading in tendons and ligaments is a growing area of interest in biomechanics. Prior models and experiments suggest that shear wave speed primarily depends on the apparent shear modulus (i.e., shear modulus accounting for contributions from all constituents) at low loads, and then increases with axial stress when axially loaded. However, differences in the magnitudes of shear wave speeds between ligaments and tendons, which have different substructures, suggest that the tissue's composition and fiber alignment may also affect shear wave propagation. Accordingly, the objectives of this study were to (1) characterize changes in the apparent shear modulus induced by variations in constitutive properties and fiber alignment, and (2) determine the sensitivity of the shear wave speed-stress relationship to variations in constitutive properties and fiber alignment. To enable systematic variations of both constitutive properties and fiber alignment, we developed a finite element model that represented an isotropic ground matrix with an embedded fiber distribution. Using this model, we performed dynamic simulations of shear wave propagation at axial strains from 0% to 10%. We characterized the shear wave speed-stress relationship using a simple linear regression between shear wave speed squared and axial stress, which is based on an analytical relationship derived from a tensioned beam model. We found that predicted shear wave speeds were both in-range with shear wave speeds in previous in vivo and ex vivo studies, and strongly correlated with the axial stress (R2 = 0.99). The slope of the squared shear wave speed-axial stress relationship was highly sensitive to changes in tissue density. Both the intercept of this relationship and the apparent shear modulus were sensitive to both the shear modulus of the ground matrix and the stiffness of the fibers' toe-region when the fibers were less well-aligned to the loading direction. We also determined that the tensioned beam model overpredicted the axial tissue stress with increasing load when the model had less well-aligned fibers. This indicates that the shear wave speed increases likely in response to a load-dependent increase in the apparent shear modulus. Our findings suggest that researchers may need to consider both the material and structural properties (i.e., fiber alignment) of tendon and ligament when measuring shear wave speeds in pathological tissues or tissues with less well-aligned fibers.

Light-driven core-shell fiber actuator based on carbon nanotubes/liquid crystal elastomer for artificial muscle and phototropic locomotion

Soft actuators controlled by untethered methods have aroused growing attention on account of their flexibility and controllability. Soft actuators shaped in a one-dimensional structure are highly desired in diverse practical applications. In this paper, we fabricate a new core-shell CNTs@LCE fiber soft actuator made of a liquid crystal elastomer (LCE) fiber coating with carbon nanotubes (CNTs) shell. Thanks to the outstanding photothermal conversion capacity of CNTs and remarkable thermal-contraction characteristic of LCE, the obtained core-shell CNTs@LCE fiber actuator can be controlled by near-infrared light with excellent phototropic bending to arbitrary directions, lifting loads more than 4600 times of its own weight and acting as artificial muscle to control the feature of biomimetic elbow and gripper with loads. More intriguingly, the core-shell CNTs@LCE fiber can fulfill unprecedented photo-driven phototropic locomotion including tracking the moving light source, climbing a slanted surface, and optically steering as well. The involved unique photo-driven phototropic movement mechanism has been revealed experimentally and theoretically, which is highly expected to guide the fabrication of other soft smart fiber actuators for advanced applications.

Mid-infrared soliton self-frequency shift in chalcogenide glass.

Emerging applications in the mid-infrared (MIR) stimulate the growth and development of novel optical light sources. Soliton self-frequency shift (SSFS) in soft glass fiber currently shows great potential as an efficient approach toward the generation of broadly tunable femtosecond pulses in the MIR. In this work, we demonstrate a highly efficient tunable soliton source based on SSFS in chalcogenide glass. We show a simple and fully fiberized system to generate these continuously tunable Raman solitons over a broad spectral range of 2.047-2.667 µm, which consumes no more than 87 pJ per pulse. The spectral measurements suggest that the generated pulses are as short as 62 fs with a maximum power conversion efficiency of 43%. This result is realized thanks to an 8 cm long As2S3 microstructure optical fiber tapered into a microwire. Thanks to their broad transparency, their high nonlinearity, and their adjustable chromatic dispersion, chalcogenide microwires are promising components for the development of compact and highly efficient MIR optical sources with low power consumption.