6 research outputs found
Design and mechanics of stackable auxetic S-shaped structures
No full text[EN] The emerging auxetic lattices, driven by contemporary advancements in additive manufacturing, have garnered significant attention, with an emphasis on improving structural performance and energy absorption efficiencies while mitigating the contributions of material nonlinearities and instabilities. This research advances the state of the art of thin-strut auxetic structures by introducing a stacking schema to realize 3D S-shaped polystructures with rigid-body motion-dominated deformation, spatial symmetry, and persistent auxeticity. Several generations of these polystructures were 3D printed using vat photopolymerization with varying strut thickness ranging from 1 mm to 3 mm. The additively manufactured structures were mechanically tested under quasi-static and impact loading scenarios, providing physical evidence for the foreseen structural behaviors discussed above. The polystructures yielded load-bearing-to-mass ratios of 4.6 kN/kg, 7.6 kN/kg, and 12.3 kN/kg for t1, t2, and t3, respectively, with less than 10 g of weight, a result of the rigid body motion and the asymmetric rotation of the polystructure beams. Additionally, the impact response highlighted a structure-to-material transition, resulting in similar force maxima for t1 and t2, with 9 and 10 N (structure-dominated), whereas t3 reported a force of up to 49 N (material-dominated). However, irrespective of the strut thickness, the negative Poisson's ratio remained nearly unchanged (-0.22 +/- 0.02), exemplifying the importance of the structural mechanics substantiated by the specific topological design of S-shaped unit cells. The research findings paved the way for the translational potential of S-shaped polystructures in practical applications for mitigating impact, including civilian and military loading conditions.The authors acknowledge the support of the National Science Foundation under Grant No. 2035663 (G.Y.) . Funding from the U.S. Department of Defense (W911NF1410039, W911NF1810477, W911NF2310150, and N00174-23-1-0009) is also acknowledged. The authors are also grateful for internal funding from San Diego State University and Universidad Carlos III de Madrid. In particular, this work was supported by the MCIN/AEI/10.13039/501100011033 and "European Union NextGenerationEU/PRTR" under grant PDC2021-121368-C21; the MCIN/AEI/10.13039/501100011033 under grants PID2020-112628RA-I00 and PID2020-118480RB-C22.Rufo-Martin, C.;Infante-García, Diego;Diaz-Alvarez, J.;Miguelez, MH.;Youssef, G. (2026). Design and mechanics of stackable auxetic S-shaped structures. European Journal of Mechanics - A/Solids. 116. https://doi.org/10.1016/j.euromechsol.2025.105874S11
Isolation and identification of bacteria from blood within 12 h using standard laboratory equipment
No full textSepsis has an incidence of 50 million cases per year and represents a significant cause of morbidity and mortality worldwide. Current diagnostic methods rely on blood drawn directly into blood culture media in hemoculture bottles, followed by culturing, often taking days to yield results and failing to meet urgent clinical needs. We present here a protocol for isolating and identifying bacteria from blood within 12 h after sampling, bypassing prior hemocultures. Starting from blood added into blood culture media, according to standard hospital sampling practice, we isolated up to 85% of bacteria at clinically-relevant concentrations in less than 15 min using an optimized centrifugation protocol. Subsequent overnight culture of the isolated bacteria on chromogenic agar plates enabled species identification of five of the most prevalent sepsis-causing bacteria. The rapidity and simplicity of the protocol may accelerate the diagnostic pipeline for sepsis patients. Moreover, the use of standard laboratory equipment may enable direct translation to clinical praxis and concatenation with downstream assays for antibiotic susceptibility testing.QC 20250728</p
Microfluidic Detection of < 400 CFU/ML E. COLI in Whole Blood Within One Hour
No full textWe report a novel workflow for the isolation of bacteria from whole blood samples. We detected E. coli from 50 μL of whole blood in concentrations as low as 400 CFU/mL in less than 1 h using a microfluidic device. The method presented consists of reducing the number of blood cells found in whole blood by selectively lysing the blood cells with a solution of saponin and sodium cholate. We demonstrate that the bacteria grow during the time of loading in the microchip and can continue to be grown afterwards on the chip. Additionally, we show our approach is compatible with some of the most common sepsis-causing bacteria. The method can half the bacterial culture time needed for antibiotic susceptibility testing (AST) of bloodstream infections.</p
Postmortem analysis using different sensors and technologies on aramid composites samples after ballistic impact
Get PDFThis work focuses on the combination of two complementary non-destructive techniques to analyse the final deformation and internal damage induced in aramid composite plates subjected to ballistic impact. The first analysis device, a 3D scanner, allows digitalising the surface of the tested specimen. Comparing with the initial geometry, the permanent residual deformation (PBFD) can be obtained according to the impact characteristics. This is a significant parameter in armours and shielding design. The second inspection technique is based on computed tomography (CT). It allows analysing the internal state of the impacted sample, being able to detect possible delamination and fibre failure through the specimen thickness. The proposed methodology has been validated with two projectile geometries at different impact velocities, being the reaction force history on the specimen determined with piezoelectric sensors. Different loading states and induced damages were observed according to the projectile type and impact velocity. In order to validate the use of the 3D scanner, a correlation between impact velocity and damage induced in terms of permanent back face deformation has been realised for both projectiles studied. In addition, a comparison of the results obtained through this measurement method and those obtained in similar works, has been performed in the same range of impact energy. The results showed that CT is needed to analyse the internal damage of the aramid sample; however, this is a highly expensive and time-consuming method. The use of 3D scanner and piezoelectric sensors is perfectly complementary with CT and could be relevant to develop numerical models or design armours.This work has been carried out within the framework of the research project DPI2017-88166-R and RTC
2015-3887-8 of FEDER program financed by the Ministerio de Economía, Industria y Competitivida
Engineering Graduate Studies for Public Security Professionals: the Bachelor Thesis at the End of the Studies
Get PDFThis work presents the latest results concerning the Bachelor Thesis developed at the end of the fourth course in the Security Engineering Degree. A combined approach has been selected applying technological issues to crime problems, and also attending to legal and social aspects involved
Engineering Graduate Studies for Public Security Professionals: the Bachelor Thesis at the End of the Studies
Get PDFThis work presents the latest results concerning the Bachelor Thesis developed at the end of the fourth course in the Security Engineering Degree. A combined approach has been selected applying technological issues to crime problems, and also attending to legal and social aspects involve
