Highlighted Publications

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.

Paper: MobiCom 2023 | Slides: MobiCom 2023

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.

Paper: IEEE/ASME Mechatronics | Paper: Ultrasonics | Paper: IUS 2021 | Slides: IUS 2021

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.

Paper (Lens Design): Physics Review Applied | Slides (Lens Design): 178th ASA Meeting
Slides (Power Transfer Underwater): 181st ASA Meeting

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.

Paper: Applied Physics Letters | Slides: SMASIS 2020

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.

Paper: Ultrasonics | Paper: ASME JNDE | Slides: ASME QNDE 2020 | Slides: SPIE 2022

Publication List

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.
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

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

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

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

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

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

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

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

Presentations

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

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

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

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)