Signal Enhancement of Pressure-Sensitive Film Based on Localized Surface Plasmon Resonance

Pressure-sensitive films have been used for measurement in micro flow, but thin films have very limited intensity, resulting in poor signal-noise ratio (SNR). This paper presents a pressure-sensitive film whose emission signal is enhanced by silver nanoparticles (AgNPs) based on localized surface plasmon resonance (LSPR). Electronic beam evaporator and annealing furnace are used to fabricate silver nanotexture surface. PtTFPP and polystyrene are dissolved in toluene and then spin-coated on the silver nanotexture surface to prepare the pressure-sensitive films. Signal enhancement of film with AgNPs due to LSPR is analyzed and enhancement effect of samples with different particle sizes and spacer thickness are compared. Pressure and temperature calibrations are performed to assess the sensing performance of pressure-sensitive films. Pressure-sensitive films with AgNPs demonstrate signal enhancement due to LSPR and show promise for measurement in micro flow.

Biomechanical Study on the Stress Distribution of the Knee Joint After Distal Femoral Fracture Malunion With Residual Varus-valgus Deformity

BackgroundThis study aims to examine the biomechanical influence of residual varus and valgus deformity after malunion of distal femoral fractures on the knee joint. MethodsWe selected 14 adult cadaver specimens to establish the femoral fractures models and subsequently fixed them at neutral position and malunion positions, i.e. at 3°, 7° and 10° at valgus and varus positions, respectively. Ultra-low pressure sensitive film technology was used to quantitatively measure the stress distribution on the medial and lateral plateau of the tibia.ResultsAt neutral position, with 400 N vertical load applied, the stress values of the medial and lateral plateau of tibia were 1.162±0.114 MPa and 1.103±0.144 MPa, respectively. Compared with those measured at neutral position, the stress on the medial plateau of the valgus tibia significantly increased, while that on the lateral plateau of the valgus tibia significantly decreased (both P<0.05). In contrast, the stress on the lateral plateau of the valgus tibia significantly increased, while that on the medial plateau of the valgus tibia significantly decreased (both P<0.05). The medial plateau of tibia demonstrated significantly higher stress values than those on the lateral plateau at neutral position and 3°, 7°, 10° varus deformities, respectively (all P<0.05), but showed significantly lower values than the those on the lateral plateau at 3°, 7°, 10° valgus deformities, respectively (all P<0.05). ConclusionsThe residual varus and valgus deformities after mulunion of the distal femoral fracture resulted in significant changes of the stress distribution of the knee joint. Anatomical reduction and firm fixation of distal femoral fracture should be as possible to be obtained to avoid possible varus and valgus deformities.

The Use of Contact Biomechanics to Study the Intact, Proximal Row Carpectomy and Scaphoid Excision, Four Bone Fusion Wrist

The study of contact biomechanics of the wrist is a challenge. This is partly due to the relatively small size of the joint as well as the lack of space in the radiocarpal joint which makes the delivery of investigative materials such as pressure sensitive film without causing artifact, difficult. Fortunately, a number of authors have studied the intact wrist, the scapholunate ligament injured wrist, the proximal row carpectomy and the scaphoid excision, four bone fusion. Despite some contrasting findings, there are some general concepts that we understand about wrist mechanics.

Contact Stress and Linearized Modal Predictions of As-Built Preloaded Assembly

The member stiffness and pressure distribution in a bolted joint is significantly influenced by the contact area of the mechanical interface under a prescribed preload force. This research explores the influence of as-built surface profiles for nominally flat interfaces of a C-Beam assembly with two well-defined contact regions. A high-fidelity finite element model is created such that the model uncertainty is minimized by updating and calibrating the piece parts prior to the preload assembly procedure. The model is then assembled and preloaded to evaluate the contact stresses and contact area for both nominally flat and perturbed non-flat surfaces based on three-dimensional surface topography measurements. The predicted pressures are validated with digitized pressure-sensitive film measurements. The high-fidelity modeling reveals how the compliance and thickness of the pressure-sensitive film alter the measured pressures, leading to incorrect evaluations of the stresses and contact area in the joint. The resulting low-level dynamic behavior of the preloaded assembly is shown to be sensitive to the true contact area by linearizing the nonlinear finite element model about the preloaded equilibrium and performing a computational modal analysis. The resonant frequencies are validated with experimental measurements to demonstrate the effect of the contact area on the modal characteristics of the bolted assembly. Vibration modes and loading patterns exhibit varying levels of sensitivity to the contact area in the joint, leading to an improved physical understanding of the influence of contact mechanics on the low-level linear vibration modes of jointed assemblies.