Embedded Files
The Underwater Backscatter Channel: Theory, Link Budget, and Experimental Validation
The Underwater Backscatter Channel: Theory, Link Budget, and Experimental Validation
This paper explores underwater backscatter communication, a method that enables net-zero-power underwater sensing and data transmission by passively reflecting sound waves instead of generating new signals. The study develops a comprehensive analytical model to characterize how acoustic waves interact with piezoelectric transducers in underwater environments. The model, validated through simulations and real-world river experiments, accurately predicts system performance with a median deviation of 0.76 dB. These findings pave the way for scalable, long-range underwater IoT networks, useful for marine monitoring, environmental sensing, and industrial applications.
System-Level DC-to-DC Analysis and Experiments of Ultrasonic Power Transfer Through Metallic Barriers
System-Level DC-to-DC Analysis and Experiments of Ultrasonic Power Transfer Through Metallic Barriers
This study explores ultrasonic power transfer (UPT) as a wireless solution for transmitting energy through metal barriers, eliminating the need for wiring in sealed environments. Using piezoelectric transducers and a Class E amplifier, the system achieved 83% AC-to-AC efficiency and 68% DC-to-DC efficiency, delivering 17.5W through a 3 mm aluminum barrier at 1 MHz. Analytical modeling, simulations, and experiments validated the design, making it a promising technology for aerospace, marine, and industrial applications where conventional wiring is impractical.
3D-Printed Gradient-Index Phononic Crystal Lens for Underwater Acoustic Wave Focusing
3D-Printed Gradient-Index Phononic Crystal Lens for Underwater Acoustic Wave Focusing
We designed and built the first 3D-printed acoustic lens for focusing acoustic waves underwater. Our solution used a desktop 3D printer to build the metamaterial lens using common polymers such as PLA or ABS. Since our lens can focus acoustic waves and make them more directional, we could use it to design underwater wireless chargers. Our lens improved the output power of an acoustic wireless charging system by a hundred times. In addition to underwater power transfer, our lenses can be designed to focus ultrasound for in-body imaging and treatment.
Sound energy harvesting by leveraging a 3D-printed phononic crystal lens
Sound energy harvesting by leveraging a 3D-printed phononic crystal lens
Modern IoT sensors and devices need very little power to operate but replacing their batteries is inconvenient and in many situations impossible if they are in hard to reach places. IoT devices can be charged using sound, however, the available power in everyday noises needs to be focused in a small area to be harvested efficiently. We developed a sound energy harvesting system consisting of a 3D-printed acoustic lens and a piezoelectric energy harvester. The lens focuses the sound energy at the harvester enabling a thousand times more power to be harvested compared to existing solutions. Our system could generate micro-Watts of power compared to nanoWatts in existing harvesters.
Phased Array Ultrasonic Testing of Inconel 625 Produced by Selective Laser Melting
Phased Array Ultrasonic Testing of Inconel 625 Produced by Selective Laser Melting
3D printing is developing at a rapid pace and manufacturers are increasingly relying on the technology to produce functional components. However, components made using 3D printing are prone to internal defects that can lead to premature failure. We are developing ultrasonic inspection solutions that can operate with emerging manufacturing technologies such as 3D printing. Our work has showed that ultrasonic phased arrays and guided waves can detect micro-scale defects in practical aerospace components. Moving forward, we seek to build low-cost automated ultrasonic systems for imaging functional 3D printed parts.
Publication List
Publication List
2026
2026
🏆W. Akbar, A. Allam, N. Naeem, and F. Adib, "Bringing All Modulations to Underwater Backscatter via PDM-Synthesis", In Proceedings of the 2026 ACM/IEEE International Conference on Embedded Artificial Intelligence and Sensing Systems (SenSys '26). Association for Computing Machinery, New York, NY, USA, 44–58. doi: 10.1145/3774906.3800496 (Best Paper Award Runner-Up)
2025
2025
W. Akbar, A. Allam, and F. Adib, “Underwater Backscatter Networking for Subsea IoT: A Link-Budget Analysis in Practical Ocean Channels”, IEEE Journal of Oceanographic Engineering, pp. 1–15, 2025, doi: 10.1109/JOE.2025.3538946.
Y. Zakaria, A. Allam, and I. El-Kady, “Modeling material nonlinearities in ultrasonic power transmission through metals,” in Active and Passive Smart Structures and Integrated Systems XIX, SPIE, May 2025, pp. 239–254. doi: 10.1117/12.3051191
L. Yan, D. Wallen, A. Phillips, A. Allam, K. Bellur, Y. Sun, H. Pandey, H. Hu, H. Nahra, R. Balasubramaniam, “Acoustic Insights into Flow Condensation Mechanisms,” in Micro and Nanoscale Phase Change Phenomena, Pomona, CA, 2025. https://ntrs.nasa.gov/citations/20250000264
2024
2024
A. Allam, H. Patel, C. Sugino, C. Arrington, C. St. John, J. Steinfeldt, A. Erturk, & I. El-Kady, “Portable through-metal ultrasonic power transfer using a dry-coupled detachable transmitter,” Ultrasonics, vol. 141, p. 107339, Jul. 2024, doi: 10.1016/j.ultras.2024.107339.
A. Bhardwaj, A. Allam, A. Erturk, and K. G. Sabra, “Ultrasound-Powered Wireless Underwater Acoustic Identification Tags for Backscatter Communication,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 71, no. 2, pp. 304–313, Feb. 2024, doi: 10.1109/TUFFC.2023.3344638.
2023
2023
🏆W. Akbar, A. Allam, and F. Adib, “The Underwater Backscatter Channel: Theory, Link Budget, and Experimental Validation,” in Proceedings of the 29th Annual International Conference on Mobile Computing and Networking, in ACM MobiCom ’23. New York, NY, USA: Association for Computing Machinery, Oct. 2023, pp. 1–15. doi: 10.1145/3570361.3613265. (Best Paper Award)
A. Eid, J. Rademacher, W. Akbar, P. Wang, A. Allam, and F. Adib, “Enabling Long-Range Underwater Backscatter via Van Atta Acoustic Networks,” in Proceedings of the ACM SIGCOMM 2023 Conference, in ACM SIGCOMM ’23. New York, NY, USA: Association for Computing Machinery, Sep. 2023, pp. 1–19. doi: 10.1145/3603269.3604814.
A. Allam, C. L. Arrington, C. St. John, J. Steinfeldt, A. Erturk, and I. El-Kady, “System-Level DC-to-DC Analysis and Experiments of Ultrasonic Power Transfer Through Metallic Barriers,” IEEE/ASME Transactions on Mechatronics, vol. 28, no. 1, pp. 15–25, Feb. 2023, doi: 10.1109/TMECH.2022.3195973. (Preprint)
2022
2022
A. Allam, K. Sabra, and A. Erturk, “Piezoelectric Transducer Design for Simultaneous Ultrasonic Power Transfer and Backscatter Communication,” Smart Mater. Struct., vol. 31, no. 9, p. 095003, Jul. 2022, doi: 10.1088/1361-665X/ac7b57. (Preprint)
A. Allam, O. Alfahmi, H. Patel, C. Sugino, M. Harding, M. Ruzzene, & A. Erturk, “Ultrasonic Testing of Thick and Thin Inconel 625 Alloys Manufactured by Laser Powder Bed Fusion,” Ultrasonics, vol. 125, p. 106780, Sep. 2022, doi: 10.1016/j.ultras.2022.106780. (Full Text)
2021
2021
A. Allam, C. Sugino, M. Harding, D. P. Bishop, A. Erturk, and M. Ruzzene, “Phased Array Ultrasonic Testing of Inconel 625 Produced by Selective Laser Melting,” ASME Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems, vol. 4, no. 041006, May 2021, doi: 10.1115/1.4050963. (Full Text)
A. Allam, K. Sabra, and A. Erturk, “Sound Energy Harvesting by Leveraging a 3D-Printed Phononic Crystal Lens,” Applied Physics Letters, vol. 118, no. 10, p. 103504, Mar. 2021, doi: 10.1063/5.0030698. (Preprint)
2020
2020
A. Allam, K. Sabra, and A. Erturk, “3D-Printed Gradient-Index Phononic Crystal Lens for Underwater Acoustic Wave Focusing,” Physical Review Applied, vol. 13, no. 6, p. 064064, Jun. 2020, doi: 10.1103/PhysRevApplied.13.064064. (Full Text)
A. Allam, K. G. Sabra, and A. Erturk, “Aspect Ratio-Dependent Dynamics of Piezoelectric Transducers in Wireless Acoustic Power Transfer,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 67, no. 5, pp. 984–996, May 2020, doi: 10.1109/TUFFC.2019.2962711. (Preprint)
2019
2019
S. Alan, A. Allam, and A. Erturk, “Programmable Mode Conversion and Bandgap Formation for Surface Acoustic Waves Using Piezoelectric Metamaterials,” Applied Physics Letters, vol. 115, no. 9, p. 093502, Aug. 2019, doi: 10.1063/1.5110701. (Preprint)
2017
2017
A. Allam, A. Elsabbagh, and W. Akl, “Experimental Demonstration of One-Dimensional Active Plate-Type Acoustic Metamaterial with Adaptive Programmable Density,” Journal of Applied Physics, vol. 121, no. 12, p. 125106, Mar. 2017, doi: 10.1063/1.4979020. (Accepted Version)
2016
2016
A. Allam, A. Elsabbagh, and W. Akl, “Modeling and Design of Two-Dimensional Membrane-type Active Acoustic Metamaterials with Tunable Anisotropic Density,” The Journal of the Acoustical Society of America, vol. 140, no. 5, pp. 3607–3618, Nov. 2016, doi: 10.1121/1.4966627. (Preprint)
Proceedings
Proceedings
Y. Zakaria, A. Allam, and I. El-Kady, “Modeling material nonlinearities in ultrasonic power transmission through metals,” in Active and Passive Smart Structures and Integrated Systems XIX, SPIE, May 2025, pp. 239–254. doi: 10.1117/12.3051191
A. Allam et al., “Detachable Dry-Coupled Ultrasonic Power Transfer Through Metallic Enclosures,” in 2021 IEEE International Ultrasonics Symposium (IUS), Sep. 2021, pp. 1–3. doi: 10.1109/IUS52206.2021.9593569.
E. Kohtanen, C. Sugino, A. Allam, A. Erturk, and I. El-Kady, “Computational Optimization of Mechanical Energy Transduction (COMET) Toolkit,” in 2021 IEEE International Ultrasonics Symposium (IUS), Sep. 2021, pp. 1–3. doi: 10.1109/IUS52206.2021.9593575.
C. Sugino et al., “Experimental Validation of Crosstalk Minimization in Metallic Barriers with Simultaneous Ultrasonic Power and Data Transfer,” in 2021 IEEE International Ultrasonics Symposium (IUS), Sep. 2021, pp. 1–3. doi: 10.1109/IUS52206.2021.9593351.
A. Allam, K. Sabra, and A. Erturk, “Enhanced Sound Energy Harvesting by Leveraging Gradient-Index Phononic Crystals,” presented at the ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Online, Sep. 2020. doi: 10.1115/SMASIS2020-2411. (Slides)
A. Allam, K. Sabra, and A. Erturk, “Comparison of various models for piezoelectric receivers in wireless acoustic power transfer,” in Active and Passive Smart Structures and Integrated Systems XIII, Denver, Colorado, Mar. 2019, vol. 10967, p. 109670S. doi: 10.1117/12.2515377. (Slides)
A. Allam and T. Elnady, “Characterization of mufflers,” presented at the International congress on acoustics, Buenos Aires, Sep. 2016. Accessed: Sep. 23, 2016. (Available Online) (Slides)
Posters/Presentations
Posters/Presentations
Presentations
Presentations
O. Tayel,Y. Zakaria, A. Allam, “Rapid Prototyping of Thickness-Mode Ultrasonic Transducer for High-EFficiency Broadband Applications,” in the 190th Meeting of the Acoustical Society of America, Philadelphia, PA, 11-15 May 2026.
Emad Abdoli, A. Allam, “A Dynamic Homogenization Framework for Elastic Metamaterials,” in the 190th Meeting of the Acoustical Society of America, Philadelphia, PA, 11-15 May 2026.
A. Allam, “Acoustic Power and Communication for Extreme IoT,” in the 189th Meeting of the Acoustical Society of America, Honolulu, HI, 1-5 Dec 2025.
Y. Zakaria, O. Tayel, I. El-Kady, and A. Allam, “Modeling Thermomechanical Effects in Wireless Ultrasonic Power Transmission Through Metals,” in the 189th Meeting of the Acoustical Society of America, Honolulu, HI, 1-5 Dec 2025.
A. Tadibi, Y. Zakaria, A. Allam, “Engineering 3D-printed Meta-Polymers for High-Efficiency Ultrasound Devices,” in the 189th Meeting of the Acoustical Society of America, Honolulu, HI, 1-5 Dec 2025.
A. Tadibi, Y. Zakaria, A. Allam, "Characterizing attenuation in 3-D-printed ultrasonic Metamaterials ", 188th Meeting of the Acoustical Society of America, New Orleans, Louisiana, 18 - 23 May 2025.
A. Tadibi, Y. Zakaria, A. Allam, "Desktop 3D-printed metamaterials for MHz-range ultrasound devices ", 188th Meeting of the Acoustical Society of America, New Orleans, Louisiana, 18 - 23 May 2025.
Y. Sun, D. Wallen, L. Yan, A. Allam, K. Bellur, H. Pandey, S. Pierson, H. Hu, “Probing Flow Condensation with Acoustic Signatures,” presented at the APS Division of Fluid Dynamics Meeting Abstracts, Nov. 2024, p. A21.009. https://ui.adsabs.harvard.edu/abs/2024APS..DFDA21009S
A. Allam, K. Sabra, and A. Erturk, “Double phononic crystal lens-based enhancement of underwater power transfer,” 181st Meeting of the Acoustical Society of America, Seattle, Washington, 29 Nov - 3 Dec 2021. (Slides)
A. Allam, C. Sugino, M. Harding, D. P. Bishop, A. Erturk, and M. Ruzzene, “Ultrasonic Inspection of Additive Manufactured Components,” QNDE 2020, Virtual, Online Conference, 25 -26 Aug 2020. (Slides)
A. Allam, K. Sabra, and A. Erturk, “Controlling Underwater Sound Propagation Using 3D-Printed Phononic Crystals,” 178th Meeting of the Acoustical Society of America, San Diego, California, 2-6 Dec 2019. (Slides)
Posters/Demos
Posters/Demos
A. Allam, K. Sabra, and A. Erturk, “Gradient-Index Phononic Crystals for Manipulating Sound in Acoustic Power Transfer Applications,” Phononics 2019, Tucson, Arizona, 3-7 June 2019. (Poster)
S. Alan, A. Allam, and A. Erturk, “Surface Acoustic Wave Manipulation Using Piezoelectric Metamaterials,” Phononics 2019, Tucson, Arizona, 3-7 June 2019. (Poster)
Dissertations
Dissertations
Doctoral Dissertations
Doctoral Dissertations
A. Allam, “Acoustic Power Transfer Leveraging Piezoelectricity and Metamaterials,” Ph.D., Georgia Institute of Technology, Atlanta, GA, 2021. (Available Online) (Full Text)
Masters Theses
Masters Theses
A. Allam, “Wave Propagation Control Using Active Acoustic Metamaterials,” MSc., Ain Shams University, Cairo, 2017. doi: 10.13140/RG.2.2.10935.85924. (Full Text)
Page updated
Google Sites
Report abuse