Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

National Institute of Standards and Technology

Vibrationally state-resolved THz spectra are obtained at cryogenic temperatures for three crystalline peptide-water systems that represent different structural motifs. The systems include two types of secondary structures and a hydrophobic peptide nanopore structure. Almost all of these systems are shown to undergo exchange with water at room temperature that alters the hydrogen bonding network in ways easily detectable in the THz region at cryogenic temperatures. Stark differences are observed in the spectra of model alpha-helical and beta-sheet structures upon water removal at hydrophilic binding sites. However, within the confined pore of a hydrophobic nanotube, water in the form of helical wires has a subtle but significant impact on the phonon modes of the tube. The THz spectra are shown to easily distinguish between the different hydration states of the system that have been independently characterized by mass change measurements. Spectral comparisons with quantum chemical predictions of fully relaxed crystal structures confirm the hydration states and give detailed information about the free energies associated with dehydration. The vibrational free energies are shown to make significant contributions to the overall energy balance of the dehydration processes.

State-resolved THz spectroscopy and dynamics of crystalline peptide-water systems.

To expand the chemical capabilities of 3D printed structures generated from commercial thermoplastic printers, we have produced and printed polymer filaments that contain inorganic nanoparticles. TiO was dispersed into acrylonitrile butadiene styrene (ABS) and extruded into filaments with 1.75 mm diameters. We produced filaments with TiO compositions of 1%, 5%, and 10% (kg/kg) and printed structures using a commercial 3D printer. Our experiments suggest that ABS undergoes minor degradation in the presence of TiO during the different processing steps. The measured mechanical properties (strain and Young's modulus) for all of the composites are similar to those of structures printed from the pure polymer. TiO incorporation at 1% negatively affects the stress at breaking point and the flexural stress. Structures produced from the 5 and 10% nanocomposites display a higher breaking point stress than those printed from the pure polymer. TiO within the printed matrix was able to quench the intrinsic fluorescence of the polymer. TiO was also able to photocatalyze the degradation of a rhodamine 6G in solution. These experiments display chemical reactivity in nanocomposites that are printed using commercial 3D printers, and we expect that our methodology will help to inform others who seek to incorporate catalytic nanoparticles in 3D printed structures.

The chemical, mechanical, and physical properties of 3D printed materials composed of TiO-ABS nanocomposites.

In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in hermetically sealed dry Argon environment, FBG devices show a quadratic dependence on temperature with expanded uncertainties (k=2) of ≈500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining peak center fitting and thermal ageing of polyimide coated fibers.

Fiber Bragg Grating Based Thermometry.

We describe a vacuum apparatus for determining the outgassing rate into vacuum, the diffusion coefficient, and the amount of gas absorbed for various materials. The diffusion coefficient is determined from a model applied to time-dependent desorption data taken using a throughput method. We used this method to determine the diffusion coefficient, , for HO in 3-D printed acrylonitrile butadiene styrene (ABS). We found  = 8.3 × 10 cm/s ± 1.3 × 10 cm/s ( = 1; 67% confidence interval) at 23.2 °C. This result was compared to the diffusion coefficient determined another by a gravimetric method, in which the sample weight was monitored as it absorbed gas from the atmosphere. The two methods agreed to within 3%, which is well within the uncertainty of the measurement. We also found that at least 80% of the atmospheric gas (air) absorbed by the ABS is water. The total amount of all atmospheric gas absorbed by ABS was about 0.35% by weight when exposed to ambient air in the laboratory, which was at a pressure of 101 kPa with a relative humidity of 57% at 22.2 °C.

Gas Uptake of 3-D Printed Acrylonitrile Butadiene Styrene (ABS) Using a Vacuum Apparatus Designed for Absorption and Desorption Studies.

We present recent work aimed at creating a standard for the dynamic measurement of pressure. A near-IR laser spectroscopy system is demonstrated for measuring 8 cm in 50 μs with a 4 kHz repetition rate.

Precision Spectroscopy to Enable Traceable Dynamic Measurements of Pressure.

Resistance thermometry provides a time-tested method for taking temperature measurements that has been painstakingly developed over the last century. However, fundamental limits to resistance-based approaches along with a desire to reduce the cost of sensor ownership and increase sensor stability has produced considerable interest in developing photonic temperature sensors. Here we demonstrate that silicon photonic crystal cavity-based thermometers can measure temperature with uncertainities of 175 mK ( = 1), where uncertainties are dominated by ageing effects originating from the hysteresis in the device packaging materials. Our results, a ≈ 4-fold improvement over recent developments, clearly demonstate the rapid progress of silicon photonic sensors in replacing legacy devices.

Towards Replacing Resistance Thermometry with Photonic Thermometry.

The push to advance efficient, renewable, and clean energy sources has brought with it an effort to generate materials that are capable of storing hydrogen. Metal-organic framework materials (MOFs) have been the focus of many such studies as they are categorized for their large internal surface areas. We have addressed one of the major shortcomings of MOFs (their processibility) by creating and 3D printing a composite of acrylonitrile butadiene styrene (ABS) and MOF-5, a prototypical MOF, which is often used to benchmark H uptake capacity of other MOFs. The ABS-MOF-5 composites can be printed at MOF-5 compositions of 10% and below. Other physical and mechanical properties of the polymer (glass transition temperature, stress and strain at the breaking point, and Young's modulus) either remain unchanged or show some degree of hardening due to the interaction between the polymer and the MOF. We do observe some MOF-5 degradation through the blending process, likely due to the ambient humidity through the purification and solvent casting steps. Even with this degradation, the MOF still retains some of its ability to uptake H, seen in the ability of the composite to uptake more H than the pure polymer. The experiments and results described here represent a significant first step toward 3D printing MOF-5-based materials for H storage.

Toward 3D Printed Hydrogen Storage Materials Made with ABS-MOF Composites.

We describe our progress in developing the infrastructure for traceable transient measurements of pressure. Towards that end, we have built and characterized a dual diaphragm shock tube that allows us to achieve shock amplitude reproducibility of approximately 2.3 % for shocks with Mach speeds ranging from 1.26 to 1.5. In this proof-of-concept study we use our shock tube to characterize the dynamic response of photonic sensors embedded in polydimethylsiloxane (PDMS), a material of choice for soft tissue phantoms. Our results indicate that the PDMS-embedded photonic sensors response to shock evolves over tens to hundreds of microseconds time scale making it a useful system for studying transient pressures in soft tissue.

Towards Traceable Transient Pressure Metrology.

In recent years, silicon photonic platforms have undergone rapid maturation enabling not only optical communication but complex scientific experiments ranging from sensors applications to fundamental physics investigations. There is considerable interest in deploying photonics-based communication and science instruments in harsh environments such as outer space, where radiation damage is a significant concern. In this study, we have examined the impact of cobalt-60 γ-ray radiation up to 1 megagray (MGy) absorbed dose on silicon photonic devices. We do not find any systematic impact of radiation on passivated devices, indicating the durability of passivated silicon devices under harsh conditions.

Zeeshan Ahmed

Physical Measurement Laboratory

National Institute of Standards and Technology

Fabrication and Testing of Photonic Thermometers

Zeeshan Ahmed

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Physical Measurement Laboratory

National Institute of Standards and Technology

Fabrication and Testing of Photonic Thermometers

Physical Measurement Laboratory