Simultaneous Force Measurements Research Articles

Abstract 105: Increased Dynamic Mechanical Energy Dissipation in Human Abdominal Aortic Aneurysm

Objectives: Individualized patient rupture risk for abdominal aortic aneurysms (AAA) remains elusive due to a limited understanding of the biomechanical events that trigger aneurysm growth and aortic wall failure. To date there has been a paucity of data describing how physiologic pulsatile energy is stored (E') and lost (E'') from AAA tissue. Our hypothesis is that AAA tissue dissipates more cyclic energy at a physiologic frequency, as determined by (E''/ E'), when compared to healthy aortic tissue. Methods: Human healthy aortic and AAA samples were obtained from cadaveric and surgical specimens. Specimens were stored at 4 o C in 0.9%NS and mechanically tested within 36 hrs of explant. Uniaxial mechanical testing (ADMET BioTense) was performed in the circumferential orientation with the tissue pre-loaded to an equivalent physiologic stress of a 5 cm at a 110 mmHg mean pressure. A sinusoidal ±5% strain was applied at 1 Hz for 40 cycles with simultaneous force measurements. After mechanical testing, immunohistochemical staining was performed to confirm tissue viability. Results: AAA tissue was significantly stiffer when compared to healthy aorta, as demonstrated by a greater average static modulus (E) 1555.4 ± 384 vs. 970 ± 128 kPa (n=5, p=0.03). Dynamic testing of the AAA tissue noted a significantly greater energy loss (E'') 137.8±36.7 vs. 43.1±21.7 (p<0.01) and loss ratio (E''/ E') 0.090 ± 0.023 vs. 0.044 ± 0.023 (p=0.02), when compared to normal specimens. Figure #1 compares the static modulus (E) to the loss ratio (E''/ E') for the aortic tissue specimens. Histologic analysis confirmed tissue viability during of all specimens. Conclusions: Our data demonstrates that AAA tissue dissipates more energy (E'') and has a greater energy loss ratio (E''/ E'), suggesting that more pulsatile energy is dissipated in diseased tissue. Future work is needed to determine how this energy dissipation influences the biologic pathogenesis of AAA growth and rupture.

Sarcomere length dependent effects on the interaction between cTnC and cTnI in skinned papillary muscle strips

Sarcomere length dependent activation (LDA) of myocardial force development is the cellular basis underlying the Frank-Starling law of the heart, but it is still elusive how the sarcomeres detect the length changes and convert them into altered activation of thin filament. In this study we investigated how the C-domain of cardiac troponin I (cTnI) functionally and structurally responds to the comprehensive effects of the Ca2+, crossbridge, and sarcomere length of chemically skinned myocardial preparations. Using our in situ technique which allows for simultaneous measurements of time-resolved FRET and mechanical force of the skinned myocardial preparations, we measured changes in the FRET distance between cTnI(167C) and cTnC(89C), labeled with FRET donor and acceptor, respectively, as a function of [Ca2+], crossbridge state and sarcomere length of the skinned muscle preparations. Our results show that [Ca2+], cross-bridge feedback and sarcomere length have different effects on the structural transition of the C-domain cTnI. In particular, the interplay between crossbridges and sarcomere length has significant impacts on the functional structural change of the C-domain of cTnI in the relaxed state. These novel observations suggest the importance of the C-domain of cTnI and the dynamic and complex interplay between various components of myofilament in the LDA mechanism.

Regenerated Bragg Gratings in Panda Fibers for Simultaneous Temperature and Force Measurements at High Temperatures

Simultaneous temperature and force measurements in an extended temperature range up to 500 °C were shown with a regenerated fiber Bragg grating in a polarisation maintaining fiber of type Panda. Type I gratings in Panda fibers were regenerated under application of a high temperature annealing process. During the first temperature cycle, a distinct hysteresis of the fiber's birefringence with temperature was observed, but reproducible dependencies of the birefringence on temperature were shown for subsequent temperature cycles. The birefringence of the fiber at room temperature was nearly doubled compared to the pristine fiber, and showed linear temperature dependencies below and above 500 °C, but with different sensitivities in both temperature ranges. A change in the temperature dependence of the birefringence can be explained by the crossing of the transition temperature of the stress applying parts (SAP) at around 500 °C. Below this temperature, measurements of temperature and applied axial forces showed reproducible and approximately linear responses of the sensor element, allowing a 2 × 2 matrix approach for simultaneous temperature and longitudinal load measurements to be applied in this temperature range. Above 500 °C, in contrast, the SAPs become viscous, resulting in a viscoelastic behaviour of the fiber.

Approaching Free Fall on Two Degrees of Freedom: Simultaneous Measurement of Residual Force and Torque on a Double Torsion Pendulum.

A torsion pendulum with 2 soft degrees of freedom (DOFs), realized by off-axis cascading two torsion fibers, has been built and operated. This instrument helps characterize the geodesic motion of a test mass for LISA Pathfinder or any other free-fall space mission, providing information on cross talk and other effects that cannot be detected when monitoring a single DOF. We show that it is possible to simultaneously measure both the residual force and the residual torque acting on a quasifree test mass. As an example of the investigations that a double pendulum allows, we report the measurement of the force-to-torque cross talk, i.e., the amount of actuation signal, produced by applying a force on the suspended test mass, that leaks into the rotational DOF, detected by measuring the corresponding (unwanted) torque.

Simultaneous Measurement of Force and Lattice Spacing in Skinned Cardiac Fibers

This study explores the relationship between Ca2+-activated force and myofilament lattice spacing (LS) in skinned cardiac muscle fibers. LS measurements were obtained using synchrotron x-ray diffraction while isometric force was simultaneously monitored with a force transducer. Dextran T500 (3%) compressed the lattice to physiological LS of intact muscle, and sarcomere length was set to 2.1μm at pCa8 using HeNe-laser diffraction. Fibers were isolated from left-ventricle of wild-type (WT) or troponin C knock-in mice bearing the homozygous mutation Ala8Val, which causes hypertrophic cardiomyopathy (KI-cTnC-A8V+/+). Cardiac fibers from KI-TnC-A8V+/+ have been reported to have 2.5x greater myofilament Ca2+-sensitivity compared to WT. Since WT and KI fibers generate different levels of force at the same [Ca2+], they provide a powerful tool for investigating whether LS is tightly coupled to force-development. Compared to WT, KI-TnC-A8V+/+ fibers tended toward smaller LS at all [Ca2+] tested (pCa8 to 5.4). However, at pCa6.2 and 5.8, both WT and KI-TnC-A8V+/+ fibers maintained LS similar to that recorded at pCa8 in each muscle. Interestingly, WT fibers developed ∼15% of the maximal force at pCa5.8 while KI-TnC-A8V+/+ fibers developed ∼70%. Because the lattice spacing vs pCa curves are approximately parallel, these data suggest that at submaximal [Ca2+], skinned fiber force does not strictly determine the distance between thin and thick filaments and that force levels can reach up to 70% of the maximal force without shortening of LS. At higher [Ca2+] (pCa5.6, 5.4) both WT and KI-TnC-A8V+/+ fibers tended toward reduced LS, despite the markedly different levels of force in each muscle. There were no differences in TnI-PSer23,24, MyBPC-Pser282 or mitochondrial content between both muscles. Future experiments will aim at determining whether radial stiffness differs between WT and KI, and measuring kinetics and number of cross-bridges at submaximal [Ca2+].

Quantitative optical coherence elastography based on fiber-optic probe for in situ measurement of tissue mechanical properties.

We developed a miniature quantitative optical coherence elastography (qOCE) instrument with an integrated Fabry-Perot force sensor, for in situ elasticity measurement of biological tissue. The technique has great potential for biomechanics modeling and clinical diagnosis. We designed the fiber-optic qOCE probe that was used to exert a compressive force to deform tissue at the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation corresponding to the external stimulus. Simultaneous measurement of force and displacement allowed us to extract Young's modulus of biological tissue. We experimentally calibrated our qOCE instrument, and validated its effectiveness on tissue mimicking phantoms and biological tissues.

Wake structure visualization of a flapping-wing Micro-Air-Vehicle in forward flight

The present study provides an experimental visualization of the three-dimensional wake structure of a small flapping-wing Micro Air Vehicle (MAV) using a stereoscopic Particle Image Velocimetry (stereo-PIV) technique, in combination with simultaneous force measurements. Variations in several kinematic parameters and flow conditions (flapping frequency, flow speed and incidence angle) are examined to identify their effects on the wake topology. The three-dimensional wake structures were reconstructed using the temporal information of one transverse measurement plane by a ‘frozen flow’ approach, which was qualitatively validated by a spatial reconstruction method using information from different spatial planes. For the first time, the complete wake topology and evolution of this specific four-wing configuration MAV in forward flight condition is characterized experimentally. The general wake topology contains two predominant vortex structures: a U-shaped vortex ring shed from the trailing edges after instroke and an arc-shaped vortex shed from the wing tips during outstroke. These two vortex structures are shed periodically from the wing and appear quite isolated from each other. As expected, a higher reduced frequency will result in an increased unsteadiness of the wake behavior, reflected by a shorter wavelength and vortical connection. Application of an incident angle of the incoming free-stream introduces geometrical changes of the wake structure.

Simultaneous measurement of dynamic force and spatial thin film thickness between deformable and solid surfaces by integrated thin liquid film force apparatus.

Interactions involving deformable surfaces reveal a number of distinguishing physicochemical characteristics that do not exist in interactions between rigid solid surfaces. A unique fully custom-designed instrument, referred to as integrated thin liquid film force apparatus (ITLFFA), was developed to study the interactions between one deformable and one solid surface in liquid. Incorporating a bimorph force sensor with interferometry, this device allows for the simultaneous measurement of the time-dependent interaction force and the corresponding spatiotemporal film thickness of the intervening liquid film. The ITLFFA possesses the specific feature of conducting measurement under a wide range of hydrodynamic conditions, with a displacement velocity of deformable surfaces ranging from 2 μm s-1 to 50 mm s-1. Equipped with a high speed camera, the results of a bubble interacting with hydrophilic and partially hydrophobic surfaces in aqueous solutions indicated that ITLFFA can provide information on interaction forces and thin liquid film drainage dynamics not only in a stable film but also in films of the quick rupture process. The weak interaction force was extracted from a measured film profile. Because of its well-characterized experimental conditions, ITLFFA permits the accurate and quantitative comparison/validation between measured and calculated interaction forces and temporal film profiles.

Instrumentation Techniques for Studying the Horizontal Behavior of High-Speed Railways

AimIn recent years the Spanish Geotechnical Laboratory of CEDEX (Centro de Estudios y Experimentación de Obras Públicas) has developed for ADIF (Administrador de Infraestructuras Ferroviarias) a series of monitoring techniques (with different types of sensors) to be used in combination with numerical models in order to define the vertical dynamic behavior of the track structure in high-speed railways. Currently we are extending our work with the purpose of monitoring and studying also the horizontal response of the track superstructure. In this contribution we present our methods for measuring vertical and horizontal displacements and loads on the rail in high-speed railways. MethodNumerical models have been used to evaluate results from different instrumentation configurations that have been designed to measure horizontal displacements and loads on the rail. Several tests in the CEDEX real scale track box facility have also been carried out. The obtained data have been interpreted in the light of the numerical models. In this way we have been able to pick out the best configurations, which have been later put in a real high-speed rail section. Besides, we have studied relationships between simultaneous measurements of horizontal force on the rail and horizontal rail-sleeper relative displacement. A good correlation between both parameters has been observed. New tests are being carried out in the CEDEX real scale track box facility with the purpose of optimizing the developed techniques and improving the numerical model calibration. ResultsWith all these techniques we are improving the knowledge of different railway sections (sections with significant thickness of ballast, transitions slab track - ballasted track, sections with bituminous sub-ballast, etc.), and optimizing their design. New techniques for analyzing the horizontal behavior of high-speed railways have been developed based on numerical models and different tests carried out in the CEDEX real scale track box facility.

Depotentiation of intact rat cardiac muscle unmasks an Epac-dependent increase in myofilament Ca(2+) sensitivity.

Recently, a family of guanine nucleotide exchange factors have been identified in many cell types as important effectors of cyclic adenosine 3',5'-monophospahte (cAMP) signalling that is independent of protein kinase A (PKA). In the heart, investigation of exchange protein directly activated by cAMP (Epac) has yielded conflicting results. Since cAMP is an important regulator of cardiac contractility, this study aimed to examine whether Epac activation modulates excitation-contraction coupling in ventricular preparations from rat hearts. The study used 8-(4-chlorophenylthio)-2'-O-methyladenosine-3', 5'-cyclic monophosphate (cpTOME), an analogue of cAMP that activates Epac, but not PKA. In isolated myocytes, cpTOME increased Ca(2+) spark frequency from about 7 to 32/100 μm(3)/s (n = 10), P = 0.05 with a reduction in the peak amplitude of the sparks. Simultaneous measurements of intracellular Ca(2+) and isometric force in multicellular trabeculae (n = 7, 1.5 mmol/L [Ca(2+)]o) revealed no effect of Epac activation on either the amplitude of Ca(2+) transients (Control 0.7 ± 0.1 vs cpTOME 0.7 ± 0.1; 340/380 fura-2 ratio, P = 0.35) or on peak stress (Control 24 ± 5 mN/mm(2) vs cpTOME 23 ± 5 mN/mm(2), P = 0.20). However, an effect of Epac in trabeculae was unmasked by lowering extracellular [Ca(2+)]o. In these depotentiated trabeculae, activation of the Epac pathway increased myofilament Ca(2+) sensitivity, an effect that was blocked by addition of KN-93, a Ca(2+)/calmodulin-dependent protein kinase II (CaMK-II) inhibitor. This study suggests that Epac activation may be a useful therapeutic target to increase the strength of contraction during low inotropic states.

Simultaneous measurement of aerodynamic forces and kinematics in flapping wings of tethered locust

Aerodynamic and inertial forces and corresponding kinematics of flapping wings of locusts, Schistocerca americana, were investigated in a low-speed wind tunnel. The experimental setup included live locusts mounted on microbalance synchronized with a high-speed video system. Simultaneous measurements of wing kinematics and forces were carried out on three locusts at 7° angle of attack and velocities of 0 m s−1 and 4 m s−1. Time variations of flapping and pitching angles exhibit similar patterns in fore- and hindwings and among the animals. Significant tip to root variations in pitching angle are found in both wings. The locusts have much larger flapping and pitching amplitudes in still air causing larger oscillations in inertial forces. Inertial forces are added to the lift and thrust on one part of the stroke, resulting in higher reaction forces and subtracted on the other part. Plots of the lift demonstrate similar trends with and without the wind. The global maxima and peak-to-peak amplitudes in lift are about the same in both tests. However, local minima are significantly lower in still air, resulting in much smaller stroke-averaged lift. Amplitudes of thrust force oscillations are much higher in still air; consequently, the stroke-averaged thrust is higher compared to the non-zero freestream velocity case.

Effect of Chemically Adsorbed Molecules on the Viscous Friction of Nanometer-Thick Liquid Lubricant Films Coated on a Diamond-Like Carbon Surface

Nanometer-thick liquid lubricant films are used for lubrication of miniaturized mechanical systems such as hard disk drives and microelectromechanical systems. In particular at the head–disk interface of hard disk drives, the lubricant thin film is coated on a diamond-like carbon surface, and the films are usually composed of both chemically and physically adsorbed lubricant molecules. The combination of these two types of molecules leads to high lubrication performance. However, the detailed mechanism is not fully understood. The aim of this study was to clarify the effect of chemically adsorbed lubricant molecules on the viscous friction of lubricant films. Two different samples were tested: One was the lubricant film composed of both chemically and physically adsorbed molecules, and the other was the lubricant film with only physically adsorbed molecules. We used a fiber wobbling method (FWM), which we developed in our previous study, to measure the viscous friction. The FWM uses a spherical-ended glass fiber as a shearing probe and enables friction forces in the order of 0.1 nN to be measured at precisely controlled nanometer-scale gap widths. For the fair comparison of friction forces between the samples with different compositions, the contact area between the probe tip and the lubricant film must be the same. To determine the contact area in the friction measurement, we improved the FWM system to enable simultaneous measurement of friction force and contact area. Experimental results showed the 1-nm-thick layer of chemically adsorbed molecules in the lubricant film effectively reduced the viscous friction.

Effect of Low-Frequency Modulation on Deformation and Material Flow in Cutting of Metals

The deformation field, material flow, and mechanics of chip separation in cutting of metals with superimposed low-frequency modulation (<1000 Hz) are characterized at the mesoscale using high-speed imaging and particle image velocimetry (PIV). The two-dimensional (2D) system studied involves a sharp-wedge sliding against the workpiece to remove material, also reminiscent of asperity contacts in sliding. A unique feature of the study is in situ mapping of material flow at high resolution using strain fields and streaklines and simultaneous measurements of tool motions and forces, such that instantaneous forces and kinematics can be overlaid onto the chip formation process. The significant reductions in specific energy obtained when cutting with modulation are shown to be a consequence of discrete chip formation with reduced strain levels. This strain reduction is established by direct measurements of deformation fields. The results have implications for enhancing sustainability of machining processes and understanding surface deformation and material removal in wear processes.

Using a novel fixture to study of temperature and applied forces during friction stir welding

This paper aims to study the effect of rotation and travel speeds on important parameters such as temperature, and transient and stable axial and longitudinal forces in friction stir welding (FSW) of aluminum AA7075-T6 to find appropriate welding parameters. For simultaneous measurement of axial force, longitudinal force and temperature, a novel fixture is designed and manufactured, which allows force measurement in the friction stir welding (FSW) process without the need to employ expensive equipment. The results show that increasing the travel speed increases both the stable axial and longitudinal forces, whereas increasing the rotation speed decreases both of them. However, the temperature trend upon increment of translation and rotation speeds is contrary to the trend for the axial and longitudinal forces. Furthermore, transient applied forces during the dwell phase are found to be highly fluctuating and much greater compared to the stable forces. Thus, transient forces may be considered as the determining factors for choosing welding.

Multicore Fiber Sensors for Simultaneous Measurement of Force and Temperature

We demonstrate a force and temperature sensor consisting of a multicore fiber (MCF) spliced between two single-mode fibers. Increasing of the sensitivity to applied force is achieved through etching of the MCF cladding, with an overall increase of $7\times $ compared with a 125- $\mu \text{m}$ MCF device, and $12\times $ compared with a standard fiber Bragg grating (FBG). Simultaneous decoupling of force and temperature with high accuracy is demonstrated using two MCF sections with different outer diameters. This device has robust operation up to 1000 °C, making it more suitable than FBGs for extreme environments.

Simultaneous Measurement of Force and Temperature by a Multi-Position Fiber Loop Ringdown Sensor Array

A multi-sensor addressing method for fiber Bragg grating aided fiber loop ringdown (FBG-FLRD) sensor array is proposed. It is capable of simultaneous measurement of temperature and force. Light from a wavelength-swept fiber laser (WSFL) is modulated into pulsed light to illuminate FBG-FLRD sensor array. Based on the time sequence of pulsed lights reflected by fiber Bragg grating array, each FBG-FLRD sensor can be distinguished. The time interval between the trigger signal of the WSFL and the pulsed light reflected by FBG offers temperature variation information. By measuring the ringdown time of each FBG-FLRD, the loss of fiber ring induced by temperature and force can be obtained. And then simultaneous measurement can be implemented in real time. To prove the validity of the proposed system, a six elements array is experimentally validated with interrogation frequency of 27.5 Hz.

Influence of Hypoxia on Joint Action Powers during Exhaustive Cycling

The relative contribution of lower-limb muscle groups changes throughout exhaustive cycling exercise. This suggests that exercise-induced fatigue is muscle group specific. We reasoned that the additional muscular distress associated with hypoxia would alter the muscle-specificity of fatigue during exercise. PURPOSE: To determine the influence of hypoxia on joint action powers across the lower-limb during exhaustive cycling. METHODS: Nine male cyclists (mean ± SD VO2MAX 61.2 ± 3.8 ml/kg/min) pedalled to the limit of tolerance at a fixed work rate (60% of the difference between VO2MAX and gas-exchange threshold: 306 ± 14 W) and fixed cadence (88 ± 2 rpm) in two conditions: normoxia (FIO2 0.21, SaO2 95 ± 1%) and hypoxia (FIO2 0.15, SaO2 85 ± 2%). Simultaneous measurements of pedal force and joint kinematics were made for each condition. Joint-specific action powers (hip extension, hip flexion, knee extension, knee flexion, plantarflexion and dorsiflexion) were derived using inverse dynamics. Each variable was averaged during the first, middle and final 30 s of exercise for each condition. Joint action powers during normoxia were also averaged across the time periods corresponding to the hypoxic condition to allow for a normoxia-isotime comparison. RESULTS: Exercise time was reduced in hypoxia (4.1 ± 0.2 vs. 10.1 ± 1.1 min, P < 0.05). In normoxia, knee extension power and ankle plantarflexion power during the final 30 s of exercise were reduced (87 ± 4% and 92 ± 2%, respectively; P < 0.05), whereas hip extension power was increased (127 ± 4%, P < 0.05). Knee extension power during the final 30 s of exercise was reduced in hypoxia and normoxia-isotime (92 ± 4% and 94 ± 3%, respectively; P < 0.05), whereas hip extension power was increased (113 ± 5% and 109 ± 2%, respectively; P < 0.05). The changes in joint action powers were not different for hypoxia vs. normoxia-isotime (P > 0.05). CONCLUSION: The hip extensors play an important role in producing additional power when other muscle groups are fatiguing during exhaustive cycling exercise. The additional muscular distress associated with hypoxia does not appear to influence inter-muscular coordination strategies.

The Reynolds number dependency of the steady and unsteady loading on a slightly rough circular cylinder: From subcritical up to high transcritical flow state

Simultaneous measurements of the spanwise-integrated unsteady aerodynamic forces and time-averaged local surface pressures on a 2D slightly rough circular cylinder were carried out over a wide range of Reynolds numbers in the high-pressure wind tunnel in Göttingen. The Reynolds numbers of 15×103≤Re≤12×106 spanned the known flow state regimes from subcritical up to high transcritical. The surface of the cylinder had a mean relative roughness of ks/D=1.2×10−3. The results demonstrated that especially in the critical flow regime the spanwise flow was strongly three-dimensional. In this regime two discontinuities at two closely spaced Reynolds numbers were observed, coupled with critical fluctuations in the lift force and the formation of a separation bubble at each side of the cylinder. The narrowing of the wake led to a sharp decrease of the drag coefficient and a steep increase of the values for the minimum pressure coefficients and the base pressure coefficient. In the upper transition state the boundary layer separation wandered upstream, resulting in an increase of the drag coefficient and a decrease of the base pressure coefficient and the Strouhal number. All measured flow field properties reached intermediate steady plateaus in the transcritical state for Re≥1.3×106. It was also shown that the surface roughness had a strong effect on the cylinder flow; in particular the disappearance of the supercritical regime and the subsequent strong recovery of the drag coefficient in the upper transition.

Simultaneous measurements of electrophoretic and dielectrophoretic forces using optical tweezers.

Herein, charged microbeads handled with optical tweezers are used as a sensitive probe for simultaneous measurements of electrophoretic and dielectrophoretic forces. We first determine the electric charge carried by a single bead by keeping it in a predictable uniform electric field produced by two parallel planar electrodes, then, we examine same bead's response in proximity to a tip electrode. In this case, besides electric forces, the bead simultaneously experiences non-negligible dielectrophoretic forces produced by the strong electric field gradient. The stochastic and deterministic motions of the trapped bead are theoretically and experimentally analysed in terms of the autocorrelation function. By fitting the experimental data, we are able to extract simultaneously the spatial distribution of electrophoretic and dielectrophoretic forces around the tip. Our approach can be used for determining actual, total force components in the presence of high-curvature electrodes or metal scanning probe tips.

Method of simultaneous measurement of two direction force and temperature using FBG sensor head.

This paper presents a method for measuring two components of bending force and temperature using one sensor head. Indirect inference based on the spectra of two fiber Bragg gratings (FBGs) placed on a cantilever beam is used. The method was developed during work on the inverse problem of determining a nonuniform stress distribution based on FBG spectra. A gradient in the FBG stress profile results in a characteristic shape of its reflective spectrum. The simultaneous measurements of force and temperature were possible through the use of an appropriate layout of the sensor head. The spectral characteristics of the sensor's gratings do not retain full symmetry, which is due to the geometry of the sensor's head and the related difference in the distribution of the axial stress of the gratings. In the proposed approach, the change in width of the sum of the normalized transmission spectra was used to determine the value of the applied force. In the presented method, an increase in the sensitivity of this change to the force is obtained relative to the other known systems. A change in the spectral width was observed for an increase in bending forces from 0 to 150 N. The sensitivity coefficient of the spectral width to force, defined as the ratio of the change of the spectral half-width to the change in force was 2.6e-3 nm/N for the first grating and 1.2e-3 nm/N for the second grating. However, the sensitivity of the whole sensor system was 5.8e-3 nm/N, which is greater than the sum of the sensitivities of the individual gratings. For the purpose of this work, a station with a thermal chamber has been designed with a bracket on which fiber optic transducers have been mounted for use in further measurements. The sensor head in this experiment is considered to be a universal device with potential applications in other types of optical sensors, and it can be treated as a module for development through its multiplication on a single optical fiber.