A New Microsensor System for Plant Root Zone Monitoring

The objective of this work is to develop a new microsensor system that can monitor dissolved oxygen and hydration environment at the plant root zone. A miniaturized plant growth system is prepared including the root zone layer, either a porous ceramic tube or porous ceramic wafer on which the plant is grown, and an underlying fluidic channel to deliver nutrients and water to the root zone. We demonstrate the feasibility of using a flexible microsensor array for dissolved oxygen detection, and a four-electrode impedance microelectrode for wetness detection on the surface of a porous tube nutrient delivery system. The unique features of the microsensor array and microelectrodes include small size, simple structure, mechanical flexibility and multipoint sensing. The new plant root microsystem technology is anticipated being a novel tool for plant root physiology

Flexible microsensor array for monitoring dissolved oxygen and water content in the plant root zone

Control of water and oxygen (O₂) in the root zone is vital to support plant growth in the microgravity environment. The ability to control these sometimes opposing parameters in the root-zone is dependent upon the availability of sensors to detect these elements and provide feedback for control systems. In the present study we demonstrate the feasibility of using microsensor arrays on a flexible substrate for dissolved O₂ detection with two representative plant growth systems: a porous tube (PT) system and a substrate-based system. Additionally, we demonstrate using a conductivity-based 4-point microprobe (FPM) for wetness detection in both the plant growth systems. --Abstract, page iii

A Flexible Microsensor Array for Root Zone Monitoring of a Porous Tube Plant Growth System for Microgravity

Control of oxygen and water in the root zone is vital to support plant growth in the microgravity environment. The ability to control these sometimes opposing parameters in the root zone is dependent upon the availability of sensors to detect these components and provide feedback for control systems. The objective of this work was to design and build advanced sensor technology that could be adapted to future hardware systems and monitor the balance between water and oxygen availability. Here we demonstrate the feasibility of using microsensor arrays on a flexible substrate for dissolved oxygen detection, and a four-electrode impedance microprobe for surface wetness detection on the surface of a porous tube (PT) nutrient delivery system. The Flexible Dissolved Oxygen Microsensor (FDOM) reported surface oxygen concentrations that correlated with the oxygen concentrations of the solution inside the PT when operated at positive pressures. But it showed convergence to zero oxygen values at negative pressures due to inadequate water film formation on the porous tube surface. The four-electrode microprobe (FEM) is useful as a basic wetness detector as it provides a clear differentiation between dry and wet surfaces. This is important as the output of the FDOM is dramatically affected by the differences in oxygen concentrations in gas and aqueous phases. The unique features of the FDOM array and FEM include small size, simple structure, mechanical flexibility, and multipoint sensing. The demonstrated technology is anticipated to provide reliable sensor feedback monitoring specialized plant nutrient delivery systems in both terrestrial and microgravity environments

Studying the polymerisation of 2-(hydroxyethyl) methacrylate using time-domain Brillouin scattering technique

International audienceBiocompatible polymerized 2-(hydroxyethyl) methacrylate (pHEMA) is a very popular material for medical applications. There are still numerous questions to be answered concerning the polymerisation processes of HEMA upon compression [1]. For this reason, the application of non-destructive contactless time-domain Brillouin scattering (TDBS) pump-probe technique [2] to the evaluation of HEMA properties looks very promising. We report here the extension of the TDBS technique to the 3D imaging of evolution of HEMA compressed in a diamond anvil cell (DAC). First, experiments were performed using classical picosecond ultrasonic set-up with a mechanical delay line [2]. To polymerise HEMA, it was compressed to 6.5 GPa and then decompressed immediately to 0.5 GPa. After 10 minutes at this pressure it was decompressed to 0 GPa. This procedure led to the increase of the Brillouin frequency from 6.3 GHz in HEMA monomer to 11.3 GHz in pHEMA. The measurements by Raman spectrometry confirmed the polymerisation of HEMA. Then, to perform 3D imaging possible in a reasonable time, we have applied an ultrafast laser technique based on an asynchronous optical sampling (ASOPS). The maps of the Brillouin frequencies obtained using TBDS technique could significantly extend our knowledge about the earlier recognised two different states of HEMA above and below 6.5 GPa [1], which cannot be distinguished by any other technique. Moreover, it should potentially allow following in time the 3D spatial spreading of the polymerization reaction starting from the nucleation sites. In perspective, the 3D imaging of the transient processes at high pressures with nanometers depth resolution could be possible. Acknowledgments: This research is supported by the grant ANR-18-CE42-017. [1] E. Evlyukhin, et al Scientific Reports 5, 18244 (2015). [2] C. Thomsen, H.T. Graham, H.J. Maris, J. Tauc, Optics Communications 60, 55 (1986)

Studying the polymerization of 2-(hydroxyethyl) methacrylate using laser ultrasonics techniques

International audienceBiocompatible polymerized 2-(hydroxyethyl) methacrylate (pHEMA) is a very popular material for medical applications. Despite different studies, realised recently, there are still many questions to be answered concerning the polymerisation processes of HEMA upon compression, which does not require an initiator [1]. For this reason, the application of non-destructive contactless laser ultrasonic techniques to the evaluation of HEMA properties looks very promising. In this work, we present the measurements of longitudinal sound velocity in HEMA in a diamond anvil cell (DAC), using well known sub-nanosecond experimental setup. First results obtained using picosecond ultrasonics are also presented. These results are compared then for a validation

Flexible Microsensor Array for the Root Zone Monitoring of Porous Tube Plant Growth System

Control of oxygen and water in the root zone is vital to support plant growth in the microgravity environment. The ability to control these sometimes opposing parameters in the root zone is dependent upon the availability of sensors to detect these elements and provide feedback for control systems. In the present study we demonstrate the feasibility of using microsensor arrays on a flexible substrate for dissolved oxygen detection, and a 4-point impedance microprobe for surface wetness detection on the surface of a porous tube (PT) nutrient delivery system. The oxygen microsensor reported surface oxygen concentrations that correlated with the oxygen concentrations of the solution inside the PT when operated at positive pressures. At negative pressures the microsensor shows convergence to zero saturation (2.2 micro mol/L) values due to inadequate water film formation on porous tube surface. The 4-point microprobe is useful as a wetness detector as it provides a clear differentiation between dry and wet surfaces. The unique features of the dissolved oxygen microsensor array and 4-point microprobe include small and simple design, flexibility and multipoint sensing. The demonstrated technology is anticipated to provide low cost, and highly reliable sensor feedback monitoring plant growth nutrient delivery system in both terrestrial and microgravity environments

In-Situ Imaging of a Light-Induced Modification Process in Organo-Silica Films via Time-Domain Brillouin Scattering

International audienceWe applied time-domain Brillouin scattering (TDBS) for the characterization of porogen-based organosilicate glass (OGS) films deposited by spin-on-glass technology and cured under different conditions. Although the chemical composition and porosity measured by Fourier-transform infrared (FTIR) spectroscopy and ellipsometric porosimetry (EP) did not show significant differences between the films, remarkable differences between them were revealed by the temporal evolution of the Brillouin frequency (BF) shift of the probe light in the TDBS. The observed modification of the BF was a signature of the light-induced modification of the films in the process of the TDBS experiments. It correlated to the different amount of carbon residue in the samples, the use of ultraviolet (UV) femtosecond probe laser pulses in our optical setup, and their intensity. In fact, probe radiation with an optical wavelength of 356 nm appeared to be effective in removing carbon residue through single-photon absorption processes, while its two-photon absorption might have led to the breaking of Si-CH3 bonds in the OSG matrix. The quantum chemical calculations confirmed the latter possibility. This discovery demonstrates the possibility of local modifications of OSG films with a nanometric resolution via nonlinear optical processes, which could be important, among other applications, for the creation of active surface sites in the area-selective deposition of atomic layers

Evaluation of Optical and Acoustical Properties of Ba_1−xSr_xTiO₃ Thin Film Material Library via Conjugation of Picosecond Laser Ultrasonics with X-ray Diffraction, Energy Dispersive Spectroscopy, Electron Probe Micro Analysis, Scanning Electron and Atomic Force Microscopies

Wide-range continuous spatial variation of the film composition in lateral compositionally graded epitaxial films requires the development of high throughput measurement techniques for their local and non-destructive characterization with the highest possible spatial resolution. Here we report on the first application of the picosecond laser ultrasonics (PLU) technique for the evaluation of acoustical and optical parameters of lateral compositionally graded film, the Ba1−xSrxTiO3 (0 ≤ x ≤ 1) material library. The film was not dedicatedly prepared for its opto-acousto-optic evaluation by PLU, exhibiting significant lateral variations in thickness and surface roughness. Therefore, the achieved measurements of the sound velocity and of the optical refractive index, and characterization of the surface roughness confirm the robustness of the PLU technique for thin film evaluation. We hope that the first measurements of the acoustical and optical properties of epitaxial grown Ba1−xSrxTiO3 (0 ≤ x ≤ 1) by PLU technique accomplished here provide the parameters required for more extended predictive design of the phononic, photonic and phoxonic mirrors and cavities with superior properties/functionalities for novel multifunctional nanodevices

Time-domain Brillouin scattering for evaluation of materials interface inclination: Application to photoacoustic imaging of crystal destruction upon non-hydrostatic compression

Time-domain Brillouin scattering (TDBS) is a developing technique for imaging/evaluation of materials, currently used in material science and biology. Three-dimensional imaging and characterization of polycrystalline materials has been recently reported, demonstrating evaluation of inclined material boundaries. Here, the TDBS technique is applied to monitor the destruction of a lithium niobate single crystal upon non-hydrostatic compression in a diamond anvil cell. The 3D TDBS experiments reveal, among others, modifications of the single crystal plate with initially plane-parallel surfaces, caused by non-hydrostatic compression, the laterally inhomogeneous variations of the plate thickness and relative inclination of opposite surfaces. Our experimental observations, supported by theoretical interpretation, indicate that TDBS enables the evaluation of materials interface orientation/inclination locally, from single point measurements, avoiding interface profilometry. A variety of observations reported in this paper paves the way to further expansion of the TDBS imaging use to analyze fascinating processes/phenomena occurring when materials are subjected to destruction

Time-domain Brillouin scattering for the evaluation of materials interface inclination: Application to imaging of crystal degradation upon non-hydrostatic compression

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