Platinum Silicon Research Articles

Biocompatibility profile of aged pigmented and non-pigmented silicone elastomer for combined maxillofacial defects.

To assess the biocompatibility of platinum silicone elastomer A-2000 used in combined maxillofacial defects prosthesis, after being deteriorated by an accelerated aging process resembling both the extra and intraoral environment. This assessment was done indirectly on human-derived dermal and gingival tissues. One hundred eight samples of room-temperature vulcanized A-2000 platinum silicone were equally divided into extrinsically pigmented and non-pigmented groups to replicate combined maxillofacial defects. Accelerated aging was applied to pigmented samples to mimic extra- and intra-oral conditions, while non-aged counterparts served as controls. After isolating human cell lineages, dermal and gingival fibroblasts were indirectly exposed to silicone sample media. Cytotoxicity to cultured fibroblasts was assessed via MTT assay. Statistical significance was determined by repeated measures of one-way ANOVA (p < 0.01), evaluating cytotoxicity on dermal and gingival fibroblasts. MTT assay showed increased cytotoxicity in pigmented silicon samples subjected to extraoral aging compared to non-aged counterparts (p < 0.01). Non-pigmented silicon, modeling intraoral conditions, exhibited cytotoxicity after 48h (p < 0.05). Both aged and non-aged silicon extracts equally sensitized gingival fibroblasts at 72h (p < 0.001). Negative correlations between pigmented and non-pigmented silicon were observed in dermal cell growth (p > 0.05, except at 24h, r = 0.2), with accelerated aging showing minimal impact on the pigmentation effect (p > 0.05). The retrieved diminished cellular metabolic activity of platinum silicone elastomer was in an acceptable clinical range, pointing out the importance of periodic assessments of the maxillofacial prosthesis for replacement depending on aging and cytotoxic harmful cellular responses.

Effect of Organic and Inorganic Nanoparticles on Colour Stability and Mechanical Properties of Heat Vulcanised Maxillofacial Silicone Elastomer: a Comparative Study.

The purpose of this comparative study in vitro was to evaluate the effect of organic and inorganic nanoparticles on colour stability, tear strength and hardness of maxillofacial silicone elastomer at baseline and when subjected to outdoor weathering for 6 months. A total of 240 specimens were fabricated using M511 platinum silicone which were divided into total 4 groups (n = 60) based on the type of nanoparticles (control, polytetrafuoroethylene [PTFE], titanium dioxide [TiO2], zinc oxide [ZnO]) added and each group was further divided into 3 subgroups (n = 20) for colour, tear strength (TS) and hardness (H) testing. The tests were conducted and data was obtained both before and after outdoor weathering of 6 months. Minimum colour change after weathering was observed in PTFE group (∆E = 2.23). TiO2 group showed maximum TS (12.01 N/mm) followed by PTFE group (10.85 N/mm) before weathering. After weathering, maximum TS was shown by TiO2 group (12.9 N/mm) and PTFE group (12.54 N/mm). TiO2 group showed maximum hardness (24.15 shore A) before weathering and PTFE group showed maximum hardness (33.43 shore A) after weathering. Within the limitations of this study, it can be concluded that the addition of polytetrafuoroethylene nanoparticles to the polymer enhances both the optical as well as mechanical properties and can be considered favourable for the extended life of the prosthesis.

Impact of tubing material on stability and filling accuracy of biologic drug product

This article is presenting completely new observations linked to Polysorbate 80 (PS80) oxidation in biologics drug product. Indeed, we observed that, in the drug product exposed to long contact time (∼ 1 h) in platinum-cured silicon tubing during the filling, the oxidation of PS80 is dramatically accelerated compared to short contact time. The phenomenon was observed in presence of iron traces (20 ppb), but not in absence of iron (< 2 ppb) or in presence of a chelator like EDTA. Electron Paramagnetic Resonance (EPR) measurements demonstrated the presence of radicals formed during the oxidation. It was deduced that platinum-cured silicon tubing is leaching some radical initiators, most probably peroxides decomposed by the iron. Alternative filling sets made of ThermoPlastic Elastomer (TPE) were investigated, both for the impact on PS80 stability and the filling performance using a peristaltic pump. The results showed that these filling sets were indeed not causing accelerated PS80 degradation but the process was not robust enough; these filling sets being too rigid for the constraints of the peristaltic pump rollers. These results show that there is no practical tubing alternative to platinum silicone cured tubing. To avoid the impact on PS80 oxidation the potential remediations presented in the article are to avoid any trace of iron or to add a chelating agent, or to discard the vials having experimented a filling stop (> 5 min).

Experimental and theoretical heat transmission through a skin phantom using a Ruby IR therapeutic lamp.

A skin phantom model was developed and characterized to study the interaction of infrared radiation during photothermal therapy. The phantom consists of a platinum silicone matrix with polyethylene oxide containing encapsulated sodium alginate to mimic the concentration of water in human skin. The specific heat and thermal conductivity of each component were experimentally measured. A theoretical model was built with heat transfer equations to simulate the temperature distribution. The experimental results and numerical simulations show that the interaction phenomenon with infrared radiation is superficial, concentrating mostly in the epidermis and part of the dermis. This successfully replicates the actual thermal behaviour of the skin during photothermal therapy. The developed phantom adequately represents the thermal properties and response to infrared radiation of the skin, allowing its use as a surrogate model in thermal imaging and diagnostic applications.

Influence of the Annealing Environment on the Structure and Ferroelectric Properties of Lead Titanate Thin Films

Lead titanate thin films of pyrochlore phase were deposited using layer-by-layer reactive magnetron sputtering on a heated platinized silicon substrate. It was found that the pyrochlore phase transition to the perovskite phase was initiated at 700 °C, and the properties of the PbTiO3 films could be controlled by changing the annealing environment. The thin films annealed in air and oxygen environments (1.33 Pa) have a tetragonal structure. The highest values of remnant polarization and the coercive field were 38 μC/cm2 and 130 kV/cm, respectively, but the largest dielectric loss was determined for the films annealed in air. The remnant polarization, coercive field and dielectric loss were reduced when the annealing of films was performed using oxygen gas at 1.33 Pa pressure. The films annealed in vacuum showed a rhombohedral (and ferroelectric) structure with the lowest remnant polarization and coercive field values. Such a structure was not observed for lead titanate at room temperature. It was observed that the surface morphology strongly depended on the reaction rate, which was influenced by the oxygen concentration in the environment.

Assessment of the antibacterial effect of Barium Titanate nanoparticles against Staphylococcus epidermidis adhesion after addition to maxillofacial silicone

Background: Maxillofacial silicones are the most popular and acceptable material for making maxillofacial prostheses, but they are not perfect in every sense. To enhance their effectiveness, more improvements to their properties are required, such as their antimicrobial efficiency. This study assess the antibacterial effect of barium titanate nanoparticles in various percentages against staphylococcus epidermidis biofilm adhesion after addition to maxillofacial silicone. Methods: Barium titanate nanoparticles were added into VST-50 platinum silicone elastomer in four weight percentages (0.25wt%, 0.5wt%, 0.75wt% and 1wt%). 50 specimens were prepared and categorized into five groups; one control group and four experimental groups. All conducted data was statistically analyzed using (one-way ANOVA) analysis of variance, and Games-Howell multiple comparison test (significant level at p &lt; 0.05). Shapiro-Wilk and Levene’s tests were used, respectively, to evaluate the normal distribution and homogeneity of the data. Result: One-way ANOVA test revealed a highly significant difference between all groups, and Games-Howell test revealed a highly significant difference between the control group and the four experimental groups. The 0.25wt% and 0.5wt% groups revealed a highly significant difference between them and with the (0.75%wt and 0.1%wt) groups. While the 0.75wt% group revealed a significant difference with 1wt% group. Conclusions: The addition of barium titanate to VST-50 maxillofacial silicone enhanced the antibacterial activity of silicon against Staphylococcus epidermidis, and this activity seems to be concentration dependent. FTIR analysis demonstrated no chemical interaction between the Barium Titanate and the VST-50 maxillofacial silicone elastomer. SEM pictures show that the barium titanate nanopowder was effectively dispersed inside the maxillofacial silicone matrix.

Assessment of the antibacterial effect of Barium Titanate nanoparticles against Staphylococcus epidermidisadhesion after addition to maxillofacial silicone.

Background: Maxillofacial silicones are the most popular and acceptable material for making maxillofacial prostheses, but they are not perfect in every sense. To enhance their effectiveness, more improvements to their properties are required, such as their antimicrobial efficiency. This study assess the antibacterial effect of barium titanate nanoparticles in various percentages against staphylococcus epidermidis biofilm adhesion after addition to maxillofacial silicone. Methods: Barium titanate nanoparticles were added into VST-50 platinum silicone elastomer in four weight percentages (0.25wt%, 0.5wt%, 0.75wt% and 1wt%). 50 specimens were prepared and categorized into five groups; one control group and four experimental groups. All conducted data was statistically analyzed using (one-way ANOVA) analysis of variance, and Games-Howell multiple comparison test (significant level at p < 0.05). Shapiro-Wilk and Levene's tests were used, respectively, to evaluate the normal distribution and homogeneity of the data. Result: One-way ANOVA test revealed a highly significant difference between all groups, and Games-Howell test revealed a highly significant difference between the control group and the four experimental groups. The 0.25wt% and 0.5wt% groups revealed a highly significant difference between them and with the (0.75%wt and 0.1%wt) groups. While the 0.75wt% group revealed a significant difference with 1wt% group. Conclusions: The addition of barium titanate to VST-50 maxillofacial silicone enhanced the antibacterial activity of silicon against Staphylococcus epidermidis, and this activity seems to be concentration dependent. FTIR analysis demonstrated no chemical interaction between the Barium Titanate and the VST-50 maxillofacial silicone elastomer. SEM pictures show that the barium titanate nanopowder was effectively dispersed inside the maxillofacial silicone matrix.

Lead-free bismuth pyrochlore-based dielectric films for ultrahigh energy storage capacitors

We developed ultra-high energy storage density capacitors using a new class of lead-free bismuth pyrochlore-based dielectric film material systems with high breakdown strength and reliability. The 2 μm-thick pyrochlore ceramic film capacitors have demonstrated ultra-high energy densities around 90 J/cm3 with very low energy loss below 3%, which is achieved by the combination of high permittivity, pseudo-linear dielectric characteristics, and high breakdown electric field over 4.5 MV/cm. Particularly, these pyrochlore ceramic films can endure voltage strength up to ∼900 V. These noteworthy pyrochlore ceramic films are fabricated by the low-cost chemical solution deposition process which allows dielectric films to be processed on standard platinized silicon wafers. This new class of capacitors can satisfy the emergent needs for significant reduction in size and weight of capacitors with high energy storage capability in power electronics, electric vehicles, and energy storage in sustainable energy systems. Our research provides a unique and economical platform for the processing of this useful pyrochlore material in large volume for eco-friendly energy applications.

Piezoelectric thick film for power-efficient haptic actuator

Emerging haptic technology based on piezoelectric actuators enables to realize innovative tactile human–machine interface. The standard solution is based on stand-alone bulk ceramics glued directly on the haptic device. Thin-film actuators with metal–insulator–metal structure have been developed to directly integrate actuators on haptic plates. The thickness of thin films is limited to 2 μm, leading to large capacitance and, thus, too high-power consumption. To solve this issue, we developed haptic devices based on a 10 μm-thick PZT film deposited on a 0.65 mm-thick platinized silicon substrate. These thick films are made of a PZT composite slurry associated with sol-gel sol infiltration. They are dense and exhibit a permittivity of 1000 and dielectric loss lower than 0.05. Our fabricated haptic device containing three actuators connected in series exhibits an antisymmetric Lamb wave resonant mode at 62.0 kHz, in line with finite element modeling. At the limit of touch detection (1 μm out of plane deflection), the power consumption of the haptic device is 150 mW at 40 V. This represents a 15-fold consumption reduction with respect to the same haptic device made with 0.5 μm-thick PZT thin films.

Investigation of the effects of different nanoparticle additionals on the mechanical properties of silicone elastomer used in maxillofacial prosthesis

Objective: The aim of this study is to evaluate the change in the mechanical properties of silicone elastomer used in the production of maxillofacial prostheses with the addition of 3 different nanoparticles (TiO2-SiO2-ZnO).&#x0D; Material and Method: TiO2-SiO2-ZnO nanoparticles were added to the A part of the M511 Platinum (Technovent Ltd., England) silicone elastomer at a rate of 2% by weight. Test specimens were produced in sizes by ASTM D412 standards for tensile strength and percent elongation, ASTM D624 for tear strength, and ASTM D2240-68 for hardness testing. For each mechanical test, 4 groups were formed together with the control group and 3 other groups to which nanoparticles were added, and a total of 132 samples were produced, 11 samples for each group (n=11), (N=132). The data of tensile strength, elongation percentage, and tear strength tests were analyzed by Shapiro Wilk's and/or Kolmogorov Smirnov/Mann Whitney U, Kruskal Wallis-H tests; for the hardness test, the values ​​in each group showed a normal distribution within themselves, hardness test was analyzed with Oneway ANOVA/Tukey HSD tests.&#x0D; Results: The addition of TiO2 and SiO2 to the silicone elastomer significantly increased the tensile strength compared to the other groups (p

Development and characterisation of hybrid composite skin simulants based on short polyethylene fibre and bioactive glass particle-reinforced silicone

Silicone elastomers are widely recognised as artificial skins for medical prosthesis and cranial injury assessment. Since silicone is not an ideal skin simulant due to the lack of mechanical stiffness and a fibrous structure, the present study aimed to tailor the mechanical and structural characteristics of silicone by integrating biocompatible reinforcements (namely, short polyethylene fibres and bioglass particles) to develop suitable bio-integrative skin simulant candidates. The influences of short polyethylene fibres and bioglass particles in the selected platinum silicone on the mechanical properties of silicone-based composite skin simulants were investigated with various factors, including filler concentration, KMnO4 surface treatment of the polyethylene fibre, and particle size. A comprehensive assessment of the tensile, compressive, and hardness properties of the examined composites was conducted, and they were compared with the properties of human biological skin. The results exhibited that the elastic moduli and the hardness of all composites increased with the concentration of both reinforcements. While integrating only the bioglass particles had the advantage of an insignificant effect on the hardness change of the silicone matrix, the composite with polyethylene fibres possessed superior tensile elastic modulus and tensile strength compared to those of the bioglass reinforced composite. The composites with 5% untreated polyethylene fibres, KMnO4 surface-treated fibres, and bioglass reinforcements enhanced the tensile elastic moduli from the pure silicone up to 32%, 44%, and 22%, respectively. It reflected that the surface treatment of the fibres promotes better interfacial adhesion between the silicone matrix and the fibres. Moreover, the smaller bioglass particle had a greater mechanical contribution than the larger glass particle. Systematically characterised for the first time, the developed composite skin simulants demonstrated essential mechanical properties within the range of the human skin and constituted better skin alternatives than pure silicone for various biomedical applications.

Solution-processed BiFeO3 thin films with low leakage current

Bismuth ferrite (BiFeO3) is an attractive multiferroic material that shows strong ferroelectric and antiferromagnetic properties. Nevertheless, producing high-quality oriented BiFeO3 on technology-important platinized silicon substrates by low-cost solution deposition methods is still challenging. In this work, polycrystalline Mn and Ti co-doped BiFeO3 (BFO) thin films were fabricated on platinized silicon substrates by a solution deposition method. PbTiO3 nanocrystals were used as a seed layer between the electrode and the BFO thin films to induce a preferential (100) pseudocubic orientation. We show that the introduction of a PbTiO3 seed layer strongly reduces the leakage current. The films show excellent room-temperature ferroelectric properties at low frequencies (300 Hz), with epitaxial-like remanent polarization as high as 51 μC/cm2 and coercive field of 500 kV/cm.

Evaluation the Effect of Nano Yttrium Oxide Addition on the Mechanical Properties of Room Temperature-Vulcanized Maxillofacial Silicone Elastomers

Objective: This study aims to investigate the effects of yttrium oxide (Y2O3) nanopowder inclusion on the mechanical properties, including tear strength, tensile strength, elongation percentage, hardness, and surface roughness, of room temperature-vulcanized maxillofacial silicone elastomers. Materials and Method: Y2O3 nanoparticles (30–45 nm) were added to VST50F platinum silicone elastomers in two weight percentages (1 and 1.5 wt%) as tested by the pilot study that showed superior results. A total of 120 specimens were qualified and divided into the control group and experimental groups (1 and 1.5 wt% Y2O3). Each group was subdivided into four identical subgroups in accordance with intentionally performed tests (tear strength, tensile strength and elongation percentage, shore A hardness, and surface roughness). For each subgroup, 10 specimens were used for each test. Data were statistically analyzed with significance level considered at p &lt; 0.05. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were also conducted. Results and Discussion: SEM showed that NPs were distributed well within the silicon matrix. FTIR spectra proved no chemical reaction occurred between the Y2O3 NPs and VST50F silicone. Tear strength and hardness values significantly increased in the experimental groups compared with the control group. Tensile strength and surface roughness values increased non significantly. Elongation percentage values decreased non significantly. Conclusion: Incorporating Y2O3 NPs into VST50F maxillofacial silicone improved the tear strength with slight increase in tensile strength. Hardness and surface roughness increased but within accepted clinical levels. Elongation percentage slightly decreased.

Advanced Surface Probing Using a Dual-Mode NSOM-AFM Silicon-Based Photosensor.

A feasibility analysis is performed for the development and integration of a near-field scanning optical microscope (NSOM) tip–photodetector operating in the visible wavelength domain of an atomic force microscope (AFM) cantilever, involving simulation, processing, and measurement. The new tip–photodetector consists of a platinum–silicon truncated conical photodetector sharing a subwavelength aperture, and processing uses advanced nanotechnology tools on a commercial silicon cantilever. Such a combined device enables a dual-mode usage of both AFM and NSOM measurements when collecting the reflected light directly from the scanned surface, while having a more efficient light collection process. In addition to its quite simple fabrication process, it is demonstrated that the AFM tip on which the photodetector is processed remains operational (i.e., the AFM imaging capability is not altered by the process). The AFM–NSOM capability of the processed tip is presented, and preliminary results show that AFM capability is not significantly affected and there is an improvement in surface characterization in the scanning proof of concept.

Direct Patterning of Piezoelectric Thin Films by Inkjet Printing

AbstractInkjet printing is currently gaining momentum as a low‐cost and eco‐friendly additive manufacturing technique for electronics. Patterning of functional metal oxide thin films on high surface energy substrates via inkjet printing remains a challenge and requires assistance from lithographic processes. This work unveils a novel process for lithography and etching‐free patterning of lead zirconate titanate (PZT) films on pristine platinized silicon through the use of inkjet‐printed alkanethiolate‐based templates. The technique requires neither lithography nor etching, respectively, before and after PZT printing. The described process allows for feature sizes in the sub‐100 µm range with control over the thickness of the final film. Inkjet‐printed PZT displays typical ferroelectric and piezoelectric properties of solution‐derived thin films, with remnant polarization 13 µC cm−2, coercive field 58 kV cm−1, permittivity 900, dielectric losses 0.07, and effective longitudinal piezoelectric coefficient 50 pm V−1.

Electro-Thermal Simulation &amp; Characterization of a Microheater for SMO Gas Sensors

The microheater is an important part of a semiconducting metal oxide gas sensor, as its primary function is to heat up the sensitive layer to a desired temperature. The operating temperature of the sensor depends on the sensitive material used and the species of the target gases. Therefore, an accurate extraction of the sensor active area temperature as a function of the applied power is critical for device characterization. These measurements are experimentally challenging due to the extremely small sensing surface area, down to a few tens of $\mu \text{m}^{2}$ , resulting in the need to develop new measurement approaches. In this paper, quantitative testing methods based on platinum and chrome silicon (CrSi) resistance thermometry, as well as a qualitative testing method (light glow) have been carried out to measure the power consumption of two different devices. CrSi has been used as a temperature sensor due to its ability to detect temperatures above 450 °C by acting as a phase-change material. For accurate measurements of temperature distribution, the presented gas sensors are equipped with three configurations of resistive temperature detectors at different locations. To further analyze a sample closed-membrane sensor, finite-element simulations were performed and an analytical model was designed and compared with experimentals. [2017–0228]

Growth of self-aligned PtSi silicide nanowires and nanoclusters on p-type Si (111) by molecular beam epitaxy

In this report Molecular Beam Epitaxy (MBE) is shown to produce self-aligned platinum silicide (PtSi) nanoclusters and nanowires on Si (111) substrate near the eutectic point (T=978°C and 67at.% Si) of the platinum silicon system. With an added silicon source in the MBE annealing chamber, the formation of two different silicon steps (straight and wave-like) is reported. The steps determine the position and the shape of the thermomigrating PtSi droplets. Nanoclusters preferentially form in the triple point of the wave-like steps while nanoclusters that form on the straight steps combine and grow into silicide nanowires.

A spectrophotometric analysis of extraoral aging conditions on the color stability of maxillofacial silicone.

Context:Surveys have reported color fading as the most frequent reasons patients given for disliking their prostheses.Aim:The aim of the study is to compare the color variation between two maxillofacial silicone elastomers after subjecting them to extraoral aging conditions.Subjects and Methods:A total of 80 samples were made from M511 Maxillofacial Rubber (Part A: Part B = 10:1) and Z004 Platinum Silicone Rubber (Part A: Part B = 1:1) and divided into two main Groups A and B (40 each). These main groups were then subdivided into five subgroups (A1B1, A2B2, A3B3, A4B4, and A5B5) (n = 8); outdoor weathering, acidic perspiration, sebum (for 6 months), and neutral soap and disinfectant (for 30 h), respectively. Baseline L*a*b* values were recorded. The samples were subjected to the extraoral aging conditions, and the L* a*b* values were recorded after the aging period using a spectrophotometer.Statistical Analysis:The intergroup comparison was done by Kruskal–Wallis test, whereas the intragroup comparison was done by Mann–Whitney test.ResultsAll groups exhibited visually detectable, mean color differences that ranged from 3.06–5.21, except for A4B4. There was no statistical significance between the two materials when subjected to extraoral aging conditions.Conclusions:Visually perceptible and clinically unacceptable color changes occur when exposed to various extraoral aging conditions except for neutral soap solution immersion, for which values of Δ E* were clinically acceptable (ΔE < 3). It can be said for all practical purposes, clinically, the choice between M511 Maxillofacial Rubber (Part A: Part B = 10:1) and Z004 Platinum Silicone Rubber (Part A: Part B = 1:1) would yield more or less the same results, with unacceptable norms in terms of color stability under extraoral aging conditions.

Porosity of maxillofacial silicone elastomers and microleakage pattern of the commercially pure Ti-silicone elastomer interface after hydrothermal cycling

Statement of problemDelamination of the maxillofacial silicone elastomer away from the commercially pure titanium (cpTi)-encapsulated magnets affects the long-term performance of the facial restoration. PurposeThe purposes of this in vitro study were to investigate the interfacial microleakage patterns of 2 maxillofacial silicone elastomers with cpTi when 3 different primers were used and to evaluate the porosity of the 2 elastomers tested. Material and methodsTo test the interfacial microleakage patterns of the 2 elastomers MDX4-4210 (EL1) and A-2006 (EL2) with cpTi when 3 metal primers, A-304 (PR1), A-320 bonding enhancer (PR2), Super-Bond C&B monomer (PR3), and ethyl-cyanoacrylate (Super Glue) were used, the bonded interfaces were observed using reflected light microscopy, and the percentage of the linear extent of leakage along the interface (%microleakage) was measured. High-resolution x-ray computed microtomography scanning was used to investigate the percentage of void volume fraction (%VF) for both silicone EL1 and EL2. The data were analyzed with 2-way ANOVA and post hoc tests (α=.05). ResultsNo statistically significant differences were found among the percentages of PR1, PR2, and PR3 microleakage, whereas ethyl-cyanoacrylate showed a statistically significant higher percentage of microleakage than either of the silicone elastomers (P<.001). EL1 medical grade elastomer groups have always had a statistically significantly higher percentage of microleakage than the EL2 platinum silicone elastomer groups (P<.001). For both elastomers, no statistically significant differences were found in %VF (P=.056). ConclusionsDifferences in mechanical properties, chemical composition, and manipulations during handling of the maxillofacial silicone elastomers can affect the linear microleakage along the cpTi-silicone elastomer bonding interface and the porosity of the silicone elastomer.

Reverse-directional explosive crystallization of microstructures in transparent film on absorbing substrate by a multipulse femtosecond radiation

Abstract The crystallization in a transparent precursor of a perovskite ferroelectric film deposited on an absorbing platinized silicon substrate initiated by multipulse femtosecond sharply focused laser beam of near-infrared spectral range is studied by transmission electron microscopy. Time dependences of the shapes of crystallized areas point to initiation of explosive crystallization with a seed on the opposite side of a heat source localized in a platinum interface layer. The radius of the crystalized semispheres varies from 150 to 900 nm, with maximal crystallization velocity up to 1.2 cm/s. Reverse direction of the spherical wave front propagation regarding to a heat source is explained in terms of the developed model based on thermal stress-induced modification of the activation energy.