Conference Proceedings and Presentations
Permanent URI for this collection
Browse
Search Collection
1 - 5 of 13825
-
PresentationInvestigation of 3D printed concrete for real-time monitoring of additive manufacturing process(SPIE, 2025-05-12)The automation of concrete construction through 3D printing (3DP) has been increasingly developed and adopted in civil engineering due to its promising advantages over traditional construction methods, which can have a tremendous societal impact by globally reducing production costs, increasing construction speed and quality, and significantly enhancing sustainability through the integration of green concrete mixes and the use of strategic geometries. However, a significant challenge hindering its widespread implementation is the high level of uncertainty introduced by the printing process, particularly regarding quality control homogeneity and consistency that stem from variability in layer bonding and the uniqueness of each specific component. Building upon our prior work in developing 3D-printable self-sensing cementitious materials by incorporating graphite powder and carbon microfibers into a cementitious matrix to enhance its piezoresistive properties, this study aims to enable real-time non-destructive evaluation of concrete 3DP by integrating the self-sensing materials as sensing nodes within conventional components to process it with self-sensing properties. In particular, we seek to locally functionalize the material with strain-responsive capabilities through integrated nodes, where the electrical resistance of the functionalized materials can be measured and directly map the strain field evolution within the structure. Three different 3D-printed zig-zagging patterns, consisting of 1, 2, and 3 strip lines, which mimic the pattern used in fabricating foil strain gauges, were investigated as conductive electrode designs to improve strain sensing performance, characterized from a series of the quasi-static and dynamic tests. Results demonstrate that it is possible to integrate 3D-printed self-sensing cementitious materials within and during a 3DP process for real-time and post-print evaluation, thus allowing the monitoring of quality, detecting changes in load paths, and identifying potential defects.
-
PresentationPiezoresistive performance of 3D printed cementitious composites doped with carbon microfibers(SPIE, 2025-05-12)The development of additive manufacturing technology in concrete construction is mainly driven by its intrinsic characteristics compared with conventional concrete. Such characteristics hold benefits related to reduced waste and workforce, and higher productivity. Despite being a promising technology, there are still challenges preventing its exponential growth in full-scale construction applications, such as the scalability of the technique and specific characteristics of the materials produced. One of the main concerns regarding the development of printed cementitious composites is related to the anisotropy of the material since their production involves the deposition of different layers of cementitious material, each one formed by filaments, which can result in weak bonds in the areas of contact. There is an opportunity in leveraging Structural Health Monitoring (SHM) technologies. SHM has been widely studied in the past years, with special attention to the development of multifunctional materials that can behave as sensors, such as cementitious and lime-based materials with piezoresistive capabilities, that can be sensitive to stress and strain variations through changes in resistivity. In these terms, the development of multifunctional cementitious materials through 3D printing (3DP) can represent an advance in the field since the higher mechanical robustness can contribute to the scalability of the sensor production, and in general terms, its widespread adoption. The current work seeks to compare the piezoresistive performance of printed specimens of cement mortar and paste produced under the same printing parameters, with and without carbon microfibers (CMF), as well as their piezoresistive behavior in comparison with cast cement-based samples, produced with the same content of carbon microfibers. As a result, the 3DP mortar samples containing CMF exhibited a significant increase in sensitivity compared to those without this carbon filler, a trend not observed in the 3DP pastes containing CMF when compared to those without. While the 3DP samples were slightly less sensitive than their manually produced counterparts, they still demonstrated strong performance as sensors.
-
PresentationDual illumination handheld photoacoustic imaging system with light emitting diode and pulsed laser diode(International society for optics and photonics (SPIE), 2025-03-20)Photoacoustic (PA) imaging is made more affordable and safer using light emitting diodes (LED). LEDs of 690 nm and 850 nm were integrated with handheld array-based transducer in the AcousticX, system (CYBERDYNE INC, Tsukuba, Japan). Performance of the system has been demonstrated for various applications such as vascular imaging of human finger and foot, tumor imaging and so on. Even with high pulse repetition rate (⁓4 kHz) illumination, the low energy per pulse of the LED (2.7 μJ/cm2 at 690 nm) limit the use of the system for laboratory or pre-clinical applications. In this work, we use a dual illumination (pulsed laser diode (PLD) and LED) setup, which extends the usability and functionality of the commercial system. The PLD (QD-Q1924-ILO-W, Quantel) which is operated at 813 nm has a max pulse energy of 7.6 mJ (@ 2k pulse repetition rate). The higher pulse energy leads to higher contrast in PA images. The wavelength of PLD is different from the wavelength of the LED of the commercial system. This enables multiwavelength imaging. In addition, the effective frame rate of the imaging system is doubled (8 kHz) when the LED and PLD light illumination pulse is appropriately delayed temporally. The contrast enhancement of LED based system with PLD is demonstrated using a graphite phantom. Imaging of phantoms of indocyanine green and methylene blue is done to demonstrate the capability of multiwavelength imaging. The doubled frame rate was demonstrated for flow imaging. The PA signal strength increases 100 -folds when PLD is used with LED. Future work is to use the PLD integrated commercial linear array system for pre-clinical imaging.
-
PresentationNanosecond-pulsed light emitting diode (LED)-based photoacoustic computed tomography(International society for optics and photonics (SPIE), 2025-03-20)Light-emitting diodes (LEDs) are emerging as a promising alternative to traditional laser sources in photoacoustic computed tomography (PACT) systems. LEDs offer several advantages including a wide range of available wavelengths, cost-effectiveness, and flexibility in system design due to low form factor. Moreover, LEDs present a lower safety hazard, eliminating the requirement for the regulatory permits usually necessary to operate high-energy class IV lasers or laser diodes. A key feature of LEDs is their variable frequency option, which allows for high contrast imaging through the averaging of multiple signals obtained from pulsed illumination. This study introduces a novel nanosecond pulsed LED array-based PACT system (LED-PACT) powered by a custom-built Nanosecond Pulsed Current Source (NSPCS). The NSPCS drives an array of 37 high-speed IR LEDs (850 nm, 1350 mW/sr), achieving rapid pulsing and simultaneous activation for enhanced illumination and improved image quality. A series of comprehensive tests were conducted using various phantoms to validate the system’s performance. The reconstructed PACT image results using a simple delay and sum (DAS) algorithm demonstrated the system’s capability to produce detailed and accurate representations of the phantoms, highlighting its potential for various biomedical applications. In conclusion, the designed LED-PACT, with its innovative design and superior performance, holds great promise for advancing the field of photoacoustic imaging. Future work will focus on optimizing the system for in vivo studies and exploring its potential for clinical applications.
-
PresentationWireless ultracompact handheld dual-mode ultrasound and photoacoustic imaging(International society for optics and photonics (SIPE), 2025-03-20)Photoacoustic (PA) imaging is a hybrid imaging modality that combines optical contrast and ultrasound (US) resolution. Dual mode ultrasound + photoacoustic imaging system based on food and drug administration (FDA) approved clinical ultrasound platform can expedite clinical translation of photoacoustic imaging. However, developing dual model US+PA imaging system is challenging, as it requires access to raw radio frequency (RF) data from the ultrasound system. On top, making the US+PA system compact and inexpensive is even more challenging. Here, we report for the first time a wireless, ultra-compact US+PA imaging system based on FDA approved clinical ultrasound platform. The developed system can be completely controlled from iOS or android devices. We have used a pulsed laser diode (PLD) for the PA imaging part. The clinical ultrasound platform is from Clarius, which is routinely used in hospitals by the clinician to image breast, musculoskeletal, nerve, thyroid and so on. The high frequency linear array transducer L15 HD3 operates at the frequency of 5–15 MHz. The PLD (QD-Q1924-ILO-W, Quantel) is operated at the wavelength of 813 nm. The transducer and the PLD is synchronized using the trigger from the transducer. We characterize the performance of the system using hair and pencil lead phantoms. The lateral resolution is approximately 300 μm. In future we would integrate the wireless transducer with light emitting diodes (LEDs) which would reduce the weight and the cost of the PA system.