Genny A. Pang

Universität der Bundeswehr München

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Ronald K. Hanson

Stanford University

Christoph Haisch

Technical University of Munich

Daniel Razansky

Institute for Biomedical Engineering

Craig T. Bowman

Stanford University

David M. Golden

MedStar Franklin Square Medical Center

Xosé Luís Deán‐Ben

Institute for Biomedical Engineering

Jan Laufer

Martin Luther University Halle-Wittenberg

Erwin Bay

Helmholtz Zentrum München

David F. Davidson

Stanford University

Alexandre Douplik

Toronto Metropolitan University

Cooperative Institutions

Technical University of Munich

Stanford University

Tampere University

Finnish Meteorological Institute

Temper (United States)

Tampere University of Applied Sciences

Universität der Bundeswehr München

Helmholtz Zentrum München

Aristotle University of Thessaloniki

Ludwig-Maximilians-Universität München

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Photoacoustic Signal Generation in Gold Nanospheres in Aqueous Solution: Signal Generation Enhancement and Particle Diameter Effects

The Journal of Physical Chemistry C (2016)

Genny A. Pang Jan Laufer Reinhard Nießner Christoph Haisch

Gold nanoparticles can be used as an exogenous contrast agent for biomedical photoacoustic (PA) imaging. The generation of PA signals in monodispersed gold nanosphere suspensions (diameters 20–150 nm) from pulsed-laser excitation (5 ns pulse width, wavelength 532 nm) was investigated experimentally and compared to signals measured in solutions of a homogeneous molecular absorber. The PA signal amplitude was found to increase linearly with excitation fluence for the homogeneous absorber and the nanospheres up to 80 nm in diameter. By contrast, the signal amplitude was found to increase quadratically with respect to fluence for larger nanospheres. In the linear regime, the PA signal amplitude in gold nanosphere suspensions was found to be on average 26% higher than that in the homogeneous absorber with identical absorption coefficient, which were measured using an integrating sphere. Furthermore, in suspensions with identical absorption coefficient, no dependence of the PA signal amplitude on nanosphere diameter was found in the linear regime, entailing that suspensions with identical extinction coefficient display a decreasing trend in PA signal amplitude with increasing nanosphere diameter due to increasing contribution of scattering. This study presents experimental evidence of some of the physical phenomena governing the photoacoustic signal generation in gold nanosphere suspensions, which may inform on approaches to molecular biomedical PA imaging.

SIGNAL (programming language)

Molar absorptivity

10.1021/acs.jpcc.6b09374

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Citations (43)

Gaseous emissions of a heavy-duty engine fueled with polyoxymethylene dimethyl ethers (OME) in transient cold-start operation and methods for after-treatment system heating

Environmental Science Advances (2022)

Alexander D. Gelner Genny A. Pang Markus Weber Christoph Haisch Harald A. Beck

Cold-start emissions of the sustainable alternative diesel fuel OME are predominantly NO x , formaldehyde, formic acid and unburned OME. Electrical heating in combination with fuel dosing is an effective method for after-treatment system heating.

Cold start (automotive)

Transient (computer programming)

10.1039/d2va00080f

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Citations (4)

Joining technology of additively manufactured components: effects on the bonding strength for the adhesive application through inner channels

Progress in Additive Manufacturing (2023)

Michael Ascher Stefan Brenner Genny A. Pang Ralf Späth

Abstract The maximum size of additively manufactured (AM) components is restricted due to the confined building space of the manufacturing machines. Component separation and subsequent joining can be an effective way of manufacturing larger components using AM processes. For joining of AM components, adhesive bonding provides great potential for not constraining the adherend’s geometry, as long as the adhesive can still be applied to the adhesive surfaces of the adherends. This work investigates the effectiveness and applicability of additively manufactured inner channels to improve the adhesive application. A circular adhesive single lap joint between a laser-based powder bed fusion (PBF-LB) component made of AlSi10Mg and a cold drawn aluminum round bar was considered. The PBF-LB components were designed with varying geometric complexity to implement different adhesive application concepts. Subsequently, the bonded joints were subjected to static tensile tests. The fracture strength of joints where the adhesive was applied by injection into AM inner channels exceeds the fracture strength of joints where the adhesive was injected into geometries manufacturable by subtractive machining, and also exceeds the fracture strength of joints where the adhesive was pre-applied.

Adhesive Bonding

Bonding strength

Bar (unit)

10.1007/s40964-023-00430-x

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Citations (0)

B1.4 A Humidity-independent Photoacoustic Sensor

E. Ambra Genny A. Pang C. Haish

10.5162/smsi2020/b1.4

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Three-dimensional tracking of lesion profile during laser surgery based on shock wave detection

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2014)

Erwin Bay Xosé Luis Dean Ben Genny A. Pang Alexandre Douplik Daniel Razansky

Lack of sensory feedback during laser surgery prevents surgeons from keeping track of the exact lesion profile and cutting depth. As a result, duration and complexity of the treatments are significantly increased. In this study we propose a new method for enabling three-dimensional tracking of the exact lesion profile, based on detection of shock waves emanating from the ablated tissue and subsequent reconstruction of the incision location using time-of-flight data obtained from multiple acoustic detectors. Ablation was performed in fresh bovine tissue samples using a Q-switched Nd-YAG laser, delivering 8 ns duration 150mJ pulses at a wavelength of 1064nm and repetition rate of 5Hz. The beam was focused by a 50mm lens on the tissue surface, which resulted in a deep cut of up to 9mm depth. The generated shock waves were detected using a spherical matrix ultrasonic array. The exact cutting profile was subsequently rendered by reconstructing the origin of shockwaves detected during the entire procedure. Different combinations of the detector positions were considered with respect to the resulting reconstruction quality. It was observed that, by utilizing at least 12 detection elements, the lesion profile could be characterized with high accuracy in all three dimensions, which was confirmed by histological evaluations. The proposed method holds promise for delivering highly precise and accurate real-time feedback during laser surgeries.

Laser Ablation

10.1117/12.2040376

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Citations (1)

Fatigue life prediction of additively manufactured AlSi10Mg based on surface roughness and residual stress

Fatigue & Fracture of Engineering Materials & Structures (2024)

Lea Strauß Genny A. Pang G. Löwisch

Abstract Laser‐based powder bed fusion (PBF‐LB) has gained prominence in the realm of additive manufacturing of metals. This technique utilizes a laser beam to consolidate powder layers, which inherently introduces high thermal gradients and rapid cooling rates. This results in characteristic process effects, including inhomogeneities, surface roughness, anisotropy, and residual stress, which play a pivotal role in altering the fatigue properties of the manufactured components. This paper presents fatigue tests involving samples of AlSi10Mg manufactured using PBF‐LB with varying surface roughness and residual stress. An approach to predict fatigue life based on stress amplitude, residual stress, and crack size is presented, using a smooth sample as a reference. An empirical model for fatigue life prediction is developed from experimentally measured values of fatigue life, peak surface roughness, and residual stress.

10.1111/ffe.14441

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Citations (1)

Towards biochemical sensing with gold nanoparticles through suppression of nonlinear photoacoustic signal generation

Photons Plus Ultrasound: Imaging and Sensing 2021 (2019)

Li Qiu Christoph Haisch Jan Laufer Genny A. Pang

We propose a new method for biochemical sensing using photoacoustic (PA) excitation of gold nanoparticles (GNPs) to achieve real-time detection of transient biomarkers. Our approach is based on the effect of a particle coating on nonlinear PA signal generation combined with our recently-developed serial PA tomographic imaging method. We have shown the ability to image the three-dimensional spatial distribution of GNPs that produce nonlinear PA signal with respect to fluence. If the occurrence of this nonlinearity is made dependent on the presence of transient biochemical markers, for example through the degradation of a nonlinearity-quenching particle coating, our serial PA tomographic imaging method can be extended for real-time three-dimensional in situ imaging of these biomarkers. Our early-stage proof-ofconcept experimental results presented here show that coating GNPs that exhibit nonlinear PA signal generation behavior is an effective method to remove the nonlinear effect. The coefficient of determination (R² ) of a linear fit to the PA signal as a function of fluence can be effectively used to differentiate the coated GNPs and the GNPs without coating. This differentiation can also be achieved using the second order coefficient to a quadratic fit to the PA signal vs. fluence data.

SIGNAL (programming language)

10.1117/12.2523417

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Citations (1)

High-Temperature Measurements of the Rate Constants for Reactions of OH with a Series of Large Normal Alkanes: n-Pentane, n-Heptane, and n-Nonane

Zeitschrift für Physikalische Chemie (2011)

Genny A. Pang Ronald K. Hanson David M. Golden Craig T. Bowman

Abstract Rate constants for the overall reactions of OH with n -pentane, n -heptane, and n -nonane were measured in shock tube experiments behind reflected shock waves. Narrow-linewidth laser absorption by OH at 306.7 nm was used in pseudo first-order experiments with temperatures between 869 to 1364 K. tert -Butyl hydroperoxide (TBHP) was used as the OH precursor. Experiments were also performed to study the kinetics of the TBHP decomposition and resulting product chemistry, and an accurate mechanism describing OH precursor chemistry effects was developed to model OH concentration time-history in the n -alkane + OH experiments. The experimental results for the n -alkane + OH rate constant measurements can be expressed as rate constants in Arrhenius form as k n -pentane + OH = 2.10 × 10 -10 exp(-2038/T[K]) (869–1364 K), k n -heptane + OH = 2.43 × 10 -10 exp(-1804/T[K]) (869–1364 K), k n -nonane + OH = 3.17 × 10 -10 exp(-1801/T[K]) (884–1352 K), each in units of cm 3 molecule -1 s -1 . The present rate constants measured for OH with n -pentane and n -heptane show agreement within 20% with recent work by Sivaramakrishnan and Michael [ J. Phys. Chem. A , 113 (2009) 5047]. The measurements of the rate constant for n -nonane + OH presented here represent the first in the literature to depict the temperature dependence of the rate constant above 800 K. The measurements of each n -alkane + OH rate constant studied were compared with two models in the literature used to estimate the rate constants of n -alkane + OH reactions. The Structure-Activity Relationship of Kwok and Atkinson [ Atmos. Environ. , 29 (1995) 1685] shows the best agreement with the current data for all three n -alkanes over the entire temperature range studied, demonstrating that this model is capable of predicting the overall rate constants for reactions of OH with n -pentane, n -heptane, and n -nonane for temperatures up to 1364 K.

Nonane

Heptane

Pentane

Alkane

Isopentane

10.1524/zpch.2011.0156

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Citations (53)

Real‐time monitoring of incision profile during laser surgery using shock wave detection

Journal of Biophotonics (2013)

Erwin Bay Xosé Luís Deán‐Ben Genny A. Pang Alexandre Douplik Daniel Razansky

Lack of sensory feedback during laser surgery prevents surgeons from discerning the exact location of the incision, which increases duration and complexity of the treatment. In this study we demonstrate a new method for monitoring of laser ablation procedures. Real‐time tracking of the exact three dimensional (3D) lesion profile is accomplished by detection of shock waves emanating from the ablation spot and subsequent reconstruction of the incision location using time‐of‐flight data obtained from multiple acoustic detectors. Here, incisions of up to 9 mm in depth, created by pulsed laser ablation of fresh bovine tissue samples, were successfully monitored in real time. It was further observed that, by utilizing as little as 12 detection elements, the incision profile can be characterized with accuracy below 0.5 mm in all three dimensions and in good agreement with histological examinations. The proposed method holds therefore promise for delivering high precision real‐time feedback during laser surgeries. (© 2013 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Laser Ablation

10.1002/jbio.201300151

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Citations (19)

Kinetic and Mechanistic Investigation of the Photocatalyzed Surface Reduction of 4-Nitrothiophenol Observed on a Silver Plasmonic Film via Surface-Enhanced Raman Scattering

ACS Applied Materials & Interfaces (2020)

Li Qiu Genny A. Pang Guangchao Zheng David Bauer Karin Wieland

Hot electrons generated by photoinduced plasmon decay from a plasmonic metal surface can reduce 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). Compared to the reduction with a reducing agent such as sodium borohydride, surface-enhanced Raman scattering (SERS) measurements were performed here to elucidate the complex molecular mechanism of the reduction in the presence of halide ions and hydrogen ions. The SERS measurements were performed using a simply prepared silver plasmonic film (AgPF), which enables monitoring of the reaction under different conditions at a solid-liquid surface and eliminates the need for the use of a reducing agent. As the concentration of H+ and Cl- could be controlled, the observation of the reaction under a systematic set of conditions was possible. Based on the kinetic traces of the intermediates, a reaction mechanism for the 4-NTP to 4-ATP reduction is suggested. Rate constants for the individual reactions are presented that fit the measured kinetic traces, and the role of hydrogen in each reaction step is characterized. This work provides clarification on the molecular transformation directly using protons as the hydrogen source and demonstrates an effective method of applying a simple and low-cost silver surface catalyst for SERS studies. Moreover, the monitoring of Cl--concentration-dependent spectra provides insight into the hot-electron conversion process during the photoreduction and strongly supports the formation of AgCl for the activation of H+.

Sodium borohydride

Reducing agent

Borohydride

10.1021/acsami.0c05977

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Citations (28)