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Beijing: Researchers 3D Print More Powerful PhotoAcoustic System

While dark-field acoustics may sound mysterious, they pertain to imaging capabilities that are helpful to researchers in a wide range of applications. In ‘A versatile dark-field acoustic-resolution photoacoustic microscopy system aided by 3D printing,’ authors Chenyao Wen, Lingyi Zhao, Tao Han, Wenzhao Li, Guangjie Zhang, and Changhui Li–all from Peking University in Beijing–are using new techniques to create a stronger, more flexible photoacoustic microscopy system.

Photoacoustic imaging relies on pulses and pressure, ultimately, to target specific images; for instance, PAT systems are popular for use by researchers involved in biomedical imaging for life science and clinical diagnosis. AR-PAM systems are even more popular for use by scientists, offering a more streamlined approach in comparison to more complex PAT systems, along with benefits such as less reconstruction artifacts, greater sensitivity, and more affordability in use.

“Until now, AR-PAM systems with different types of transducers (frequency range covering from 5 MHz to 50 MHz) have been successfully used in imaging various biological tissues, including skin, the brain, the intestine, eyes, and the abdomen of rats.”

Dark-field systems use a ‘donut-shaped’ dark-field illumination that is positioned underneath an ultrasonic transducer and can be used to eliminate undesired photoacoustic signals, while allowing PA waves; however, due to the opaque quality of the ultrasonic transducer, a customized optical condenser must be employed.

The authors point out that while previous labs have created different types of condensers—including those using internal reflection and mirror reflection—such choices are not always suitable for lab use. Here, the researchers developed a new system with inexpensive 3D printed parts and a fiber bundle for optical coupling and delivery. The new system also means that the angle of illumination is tunable, and transducers are easily replaced.

(a) The schematic of the AR-PAM system. (b) Photograph of the 3D printed optical condenser with the transducer.

“A tunable Ti:sapphire pulsed laser (LT-2211A, LOTIS TII, Minsk, Belarus) pumped by a Q-switched Nd:YAG pump laser (LS-2137/2, LOTIS TII, Minsk, Belarus) served as the illumination source, which has a repetition rate of 10 Hz and a pulse width of 16-ns. The 800 nm near-infrared (NIR) laser was generated by the pulsed Ti:sapphire laser. The fiber bundle consists of a total of 5670 multimode glass fibers (core diameter, 50 μm; NA, 0.62) with one combined terminal end (diameter, 5 mm) for laser input and nine equal branching terminal ends (diameter, 1.5 mm) for laser output,” explained the authors.

Rather than offering just a single multimode fiber, the researchers sought more power with a fiber bundle, consisting of fibers ‘randomized into nine branches.’ Each terminal was mounted around the 3D printed condenser, composed of 3D printed adjustable joints, with an ultrasonic transducer in the center.

The 3D printed condenser consists of the following:

  • Fiber holder
  • Transducer adaptor
  • Interconnecting pieces
  • Angle-adjust ring
  • Main body

The design of the condenser and the 3D printed adaptors also allowed the researchers to fit in transducers of different sizes. What is even more impressive, however, is that the overall cost to 3D print the condenser was $10 USD, with assembly completed in one hour.

“Only a few metal nuts were glued onto the condenser since 3D printing is unable to print robust fine screw threads in resin material. The 3D printing files and fiber design are available for free upon request,” explained the researchers.

For both simulation and phantom experiments, the researchers used the following measurements:

  • Illumination angle of 30 degrees
  • Outer diameter and inner diameter of the donut – 20mm and 12mm, respectively
  • Illumination patterns of fiber bundles – a circle with a diameter of 4mm
  • Inner diameter of nine circles set at 12mm

Scheme of the 3D printed condenser and the mechanism of changing the illumination angle. (a)Structural scheme of the condenser. TA, transducer adaptor; ADR, angle adjust ring; FH, fiber holder; ICP, interconnecting pieces. Multimedia view: https://doi.org/10.1063/1.5094862.1 (b) Sectional view of the holder; angle θ (marked as a green curve) between the sensor and the fiber changes following the vertical movement of the ADR, which is marked as a red twin arrow. (c) Photograph of illuminated donut patterns at three different angles of 20○, 30○, and 45○.

During simulation, the researchers realized that depth had a major impact on power of the system and specifically, optical fluence between the fiber bundle and the donut illumination.

“Although the fiber bundle has a much larger terminal for laser coupling, the coupling efficiency is generally less than that of a single multimode fiber,” concluded the researchers. “It is because there exist interfiber spaces that waste part of the illuminating laser. An alternative way is to use the so-called ‘Fused End Bundles’ by CeramOptec®, which could help increase the coupling efficiency.”

“ … the current system is more suitable for relative low frequency transducers that need smaller illumination angles. Since the 3D printing optical lens also becomes popular, we will explore methods to converge the output laser via gluing a printed lens on top of the branching fiber bundle terminal in future work.”

While scientists around the globe are engaged in spectacular research projects regarding bioprinting, new additive manufacturing processes, industrial design, and so much more, scientists are also able to create a wide range of tools to help complete many different studies—some replacing common components made by conventional methods, and others that could not have been possible otherwise.

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

The schematic of two different illumination conditions: the traditional dark-field reflection mode (left) and the fiber illuminating mode (right).

[Source / Images: ‘A versatile dark-field acoustic-resolution photoacoustic microscopy system aided by 3D printing’]

The post Beijing: Researchers 3D Print More Powerful PhotoAcoustic System appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

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Georgia Tech and Beida 3D print engineering strength origami

A 3D printing research collaboration between Georgia Institute of Technology and China’s Peking University (Beida) has yielded transformable structures that can support up to 100 times their own weight. A continuation of previous studies demonstrating self-assembling tensegrity structures, the results of this research is a step forward for engineering applications of origami structures. Origami engineering principles As pointed […]
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Researchers Make Strong, 3D Printed Expandable Origami Structures for Engineering Applications

Rearranging the same units can change a structure from one that can support a load 100 times its weight to one that will fold flat under the same load. [Image: Soft Matter]

A collaborative team of researchers from the Georgia Institute of Technology, the Beijing Institute of Technology, and Peking University are using 3D printing to directly build reconfigurable origami assemblages that can expand and fold. But even better, the 3D printed structures also have enough load-bearing capability and strength to be used in engineering applications.

In a paper published in Soft Matters, titled “3D printing of complex origami assemblages for reconfigurable structures,” the researchers explained how they used digital light processing (DLP) 3D printing to fabricate structures with hollow features.

With this method, far less support material is required for 3D printing hollow features, and softer materials, necessary for flexible structures, can be used.

The abstract of the paper reads, “Origami engineering principles have recently been applied to a wide range of applications, including soft robots, stretchable electronics, and mechanical metamaterials. In order to achieve the 3D nature of engineered structures (e.g. load-bearing capacity) and capture the desired kinematics (e.g., foldability), many origami-inspired engineering designs are assembled from smaller parts and often require binding agents or additional elements for connection. Attempts at direct fabrication of 3D origami structures have been limited by available fabrication technologies and materials. Here, we propose a new method to directly 3D print origami assemblages (that mimic the behavior of their paper counterparts) with acceptable strength and load-bearing capacity for engineering applications. Our approach introduces hinge-panel elements, where the hinge regions are designed with finite thickness and length. The geometrical design of these hinge-panels, informed by both experimental and theoretical analysis, provides the desired mechanical behavior. In order to ensure foldability and repeatability, a novel photocurable elastomer system is developed and the designs are fabricated using digital light processing-based 3D printing technology. Various origami assemblages are produced to demonstrate the design flexibility and fabrication efficiency offered by our 3D printing method for origami structures with enhanced load bearing capacity and selective deformation modes.”

Many 3D printed structures with unique properties have been inspired by origami, opening up applications in soft robotics and self-folding structures. While most origami structures mean thin sheets being joined together with binding elements like glue, the research team found a way to make several 3D assemblies in one step, without needing to connect smaller parts together. The team, led by Zeang Zhao, developed a new polymer and used geometrical design to move towards using origami for engineering structures.

To build the origami, the team developed a novel new elastomer, which makes it possible for the structure to be created from a single component. The elastic polymer material can be 3D printed at room temperature and set with UV light, which forms a soft, foldable material that can be stretched up to 100%. This material was used for the whole 3D assembly. DLP 3D printing was used to build structures, made up of various combinations of individual units of origami, without requiring any extra assembly steps.

By altering how each origami unit is connected, the structures can be designed to have different load-bearing capabilities: vitally important for applications in engineering. One of the test structures was even able to support a load that weighed 100 times more than the structure itself did. But here’s the really interesting part – just by rearranging the same individual units in a different way, the team was able to build a bridge that, under the same heavy load, would fold flat.

The structures were designed with thick panels, which were separated by hinges not unlike the creases in a piece of paper. The hinges made it possible for the angle between the panels to vary between 0° and 90°. Hinge thickness is important for a structure’s mechanical properties: if it’s too thick, it won’t fold well, while if it’s too thin, it might not be able to support the structure’s weight. In addition, the researchers made sure that the high strain and stress the structures experienced during folding was localized specifically to the hinges, so the panels would not end up deformed.

Co-authors of the paper are Zhao, Xiao Kuang, Jiangtao Wu, Qiang Zhang, Glaucio H. Paulino, H. Jerry Qi, and Daining Fang.

Discuss this research and other 3D printing topics at 3DPrintBoard.com or share your thoughts in the Facebook comments below. 

[Source: Physics World]