Guillermo Aguilar
· Department Head, Mechanical Engineering Professor, Mechanical Engineering J.M. Forsyth ChairVerifiedTexas A&M University · Mechanical Engineering
Active 1980–2026
About
Our nationally recognized faculty, researchers and professional staff are dedicated to excellence in research, education, innovation and service. Learn more about the individuals who make up the Department of Mechanical Engineering by visiting their profiles.
Research topics
- Optics
- Materials science
- Mechanics
- Composite material
- Nanotechnology
- Physics
- Thermodynamics
- Geometry
Selected publications
Optics & Laser Technology · 2026-04-20
articleOpen accessSenior authorCorresponding• Digital holography interferometry maps CW laser-induced thermocavitation in liquids. • Non-contact optical metrology enables temperature mapping at the micrometer scale. • Interferometry captures pre-cavitation heating and post-collapse thermal dynamics. • Raman and COMSOL validate heat transfer and concentration effects in solutions. • Advances optical methods for temperature, heat, and fluid flow characterization. Thermocavitation, the nucleation of vapor bubbles generated by continuous-wave (CW) laser heating in absorbing liquids, underlies a range of fluidic and optical processes. However, the transient thermal environment preceding, during, and following cavitation remains poorly characterized due to the limited spatial and temporal resolution of conventional probes. Here, we demonstrate the first use of digital holography interferometry (DHI) for quantitative, two-dimensional temperature mapping of thermocavitation in copper nitrate solutions. Operating at 693 frames per second, the DHI system resolves localized pre-cavitation heating and the rapid post-collapse cooling signature at the laser focus, followed by thermal redistribution into the bulk fluid with micrometer-scale spatial resolution. Raman spectroscopy and viscosity measurements reveal concentration-dependent modifications to solution structure and thermal diffusivity, while COMSOL simulations support the experimentally observed heat transport. Across concentrations, DHI reveals that lower-absorbing solutions exhibit earlier cavitation onset (∼ 0.2 sec vs. ∼ 0.5 sec in concentrated solutions), broader heating zones, larger absolute bubble sizes, and more substantial post-collapse redistribution. In contrast, higher concentrations confine heating near the cuvette wall because stronger optical absorption limits light penetration, producing smaller bubbles in absolute size but proportionally larger relative to the much shorter heated-zone length. Using DHI, we observe temperatures preceding bubble nucleation at the laser focus ranging from ∼ 307 to 355 °C with increasing concentration, consistent with the trend-based nucleation temperature ranges inferred from Raman spectroscopy. High-speed imaging confirms the relationship between bubble size and heated length, complementing the interferometric data. Collectively, these results establish DHI as a powerful non-contact, non-invasive technique for resolving spatiotemporal dynamics of CW laser-induced cavitation and highlight its broader potential for probing rapid, small-scale superheating and heat transfer phenomena in liquids.
Cell Biomaterials · 2025-11-05
articleOpen accessAdvanced Engineering Materials · 2025-05-29 · 1 citations
articleOpen accessSenior authorCorrespondingFabrication of laser‐induced periodic surface structures (LIPSS) with near‐submicron length scale can greatly modify the surface‐related properties of materials as shown over the past decade. The hydrophobic properties can be combined with the dense nanostructures present in LIPSS to act as hotspots for highly sensitive surface‐enhanced Raman spectroscopy (SERS) applications. In this study, usage of single and double fs laser pulse irradiation to obtain different morphologies of LIPSS is demonstrated. By controlling the polarization, fluency, and interpulse delay between fs pulses, 1D and 2D periodic nanostructures are generated on 304‐stainless‐steel substrates, and the corresponding formation mechanisms are discussed. The LIPSS‐based sensors exhibit a high contact angle of 112°, demonstrating good capability of depositing analyte molecules after evaporation for SERS detection. Furthermore, the dense hotspots present in LIPSS‐based SERS sensors can detect up to 10 −10 M concentration of Rhodamine 6G with an analytical enhancement factor of 2 × 10 7 . The substrates also demonstrated uniform and repeatable measurements with an RSD of 9.64%. The results provide insight into controlling laser‐induced submicron morphology by changing experimental parameters as a simple and cost‐effective approach for ultra‐trace detection of molecules.
Revista Española de Anestesiología y Reanimación (English Edition) · 2025-05-16
articleBone · 2025-09-04 · 4 citations
articleAdvanced Engineering Materials · 2025-08-01 · 2 citations
articleSenior authorArXiv.org · 2025-11-15
preprintOpen accessSenior authorLithium niobate is one of the most sought-after materials for nanophotonic devices, including frequency converters, modulators, and quantum light sources. Integration of lithium niobate into optical devices, however, is hampered by significant top-down fabrication challenges due to its exceptional chemical resistance. Scalable fabrication methods that preserve material quality while reducing fabrication complexity and cost are, therefore, crucial to advancing lithium niobate devices. We present a photochemical metal-organic decomposition technique for the scalable patterning of lithium niobate at ambient conditions, eliminating the need for harsh etching conditions and cleanroom protocols. The method utilizes a solution of a custom-prepared photosensitive organometallic precursor as a negative photoresist. The UV light exposure of the thin films of the precursor through a photomask, followed by rinsing with ethanol, yields amorphous patterns, which transform into crystalline lithium niobate after a calcination step. This method enables a scalable fabrication of a range of complex geometric shapes with a feature resolution down to $30\,μ\mathrm{m}$. The patterned lithium niobate structures exhibit a tunable second harmonic generation activity with an isotropic optical response. This approach offers a scalable and low-cost pathway for manufacturing lithium niobate photonics and the potential to fabricate other materials (e.g., barium titanite and lithium tantalate).
Regional lung volume changes with noninvasive positive pressure ventilation in healthy adults
Journal of Applied Physiology · 2025-02-13 · 2 citations
articleOpen accessNoninvasive positive pressure ventilation (NIPPV) is a commonly utilized intervention for acute and chronic respiratory failure. In this study, we use functional lung imaging to describe changes in regional lung ventilation and redistribution of lung volume with NIPPV. These results offer insight into the regional effects of NIPPV on volume expansion with the use of functional imaging.
2025-03-19
articleSenior authorThe creation of Laser-Induced Periodic Surface Structures (LIPSS) with near-submicron dimensions has significantly altered the surface properties of materials, as demonstrated in the past decade. These properties, particularly the hydrophobic characteristics, can be enhanced when combined with the dense nanostructures in LIPSS, making them ideal for highly Sensitive Surface-Enhanced Raman Spectroscopy (SERS) applications. However, a key challenge lies in precisely controlling the morphology of these nanostructures and their surface contact properties to effectively concentrate analyte molecules in specific regions for detection at extremely low concentrations. Here we show how single and double femtosecond laser pulse irradiation can be used to achieve different LIPSS morphologies. We generate 1D and 2D periodic nanostructures on 304 stainless steel substrates by adjusting the polarization and inter-pulse delay between fs pulses. From the preliminary experimental results, the dense hotspots in these LIPSS-based sensors allow for the detection of Rhodamine 6G at concentrations as low as 10−10 M, with an analytical enhancement factor of 2 × 107 for consistent and repeatable measurements. These findings provide important insights into the control of laser-induced submicron morphologies by adjusting experimental parameters, offering a straightforward and cost-efficient approach for detecting molecules at ultra-trace levels.
Scientific Reports · 2025-07-31 · 3 citations
articleOpen accessCryopreservation by vitrification could transform fields ranging from organ transplantation to wildlife conservation, but critical physical challenges remain in scaling this approach from microscopic to macroscopic systems, including the threat of fracture due to accumulated thermal stresses. Here, we provide experimental and computational evidence that these stresses are strongly dependent on the glass transition temperature [Formula: see text] of the vitrification solution, a property which, given the narrow band of chemistries represented within common vitrification solutions, is seldom investigated in thermomechanical analyses. We develop a custom cryomacroscope platform to image glass cracking in four aqueous solution chemistries spanning > 50 °C in [Formula: see text]; we process these images using semantic segmentation deep learning algorithms to analyze the extent of cracking in each; and we perform thermomechanical finite element simulations to disentangle the multiphysics effects driving the observed dependency, providing new insights to inform design of next-generation vitrification solutions that minimize thermal cracking risks.
Recent grants
NSF · $300k · 2020–2023
NSF · $3.7M · 2015–2022
Collaborative Research: Understanding Laser-Assisted Surface Cooling Enhancement (LASCE)
NSF · $225k · 2014–2018
EAGER: Biocompatibility of nanocrystalline YSZ transparent cranial implant
NSF · $260k · 2015–2018
NIH · $577k · 2007
Frequent coauthors
- 205 shared
J. Stuart Nelson
University of Tennessee Health Science Center
- 78 shared
Walfre Franco
University of Massachusetts Lowell
- 68 shared
Lars O. Svaasand
- 59 shared
Boris Majaron
University of Ljubljana
- 44 shared
Enrique J. Lavernia
Texas A&M University
- 37 shared
Santiago Camacho-López
Center for Scientific Research and Higher Education at Ensenada
- 36 shared
Julio C. Ramı́rez-San-Juan
- 36 shared
Kristen M. Kelly
University of California, Irvine
Education
- 2000
Postdoctoral Scholar, Biomedical Engineering
University of California Irvine
- 1999
Ph.D., Mechanical Engineering
University of California Santa Barbara
- 1995
M.S., Mechanical Engineering
University of California Santa Barbara
- 1993
B.Sc., Mechanical and Electrical Engineering
Universidad Nacional Autónoma de México (UNAM)
Awards & honors
- McDonald Mentoring Award, American Society of Mechanical Eng…
- Fellow, American Institute for Medical and Biological Engine…
- Fellow, American Society of Mechanical Engineering (ASME) (2…
- National Academy of Engineering of Mexico (2019)
- STAR Award: Educator of the Year, Society of Hispanic Profes…
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