Irradiated Spot Research Articles

I-design terahertz microfluidic chip for attomole-level sensing

We developed a nonlinear optical crystal-based compact terahertz (THz)-microfluidic chip with several I-design meta-atoms for attomole (amol)-level sensing of trace amounts of solution samples. The I-design meta-atom consists of a metallic strip with a micometer-sized gap sandwiched by other metallic strips. It is periodically arrayed in a row of 1 × 5 units. A point THz source locally generated by optical rectification at the irradiation spot of a femtosecond-pulse laser beam induces a tightly confined electric-field mode at the gap regions and modifies the resonance frequency when a microchannel fabricated along the space between the metallic strips is filled with solutions. Using this chip, we could detect minute changes in the concentration of trace amounts of ethanol- and glucose-water solutions and mineral water by measuring the shift in the resonance frequencies. We succeeded in detecting 472 amols of solutes in solutions less than 100 picoliters using an effective sensing area of 0.10 λ THz × 0.57 λ THz, which indicates an improvement of approximately one order of magnitude compared to the performance of existing chips. This technique compactifies THz-microfluidic chips with high sensitivity and would accelerate the development of microfluidics integrated with THz technology, such as lab-on-a-chip devices and THz micro total analysis systems.

A Scintillator Array Table with Spectroscopic Features.

In the framework of radioactive material handling, such as in radwaste sorting and segregation operations, the availability of a simple tool to quickly detect and locate gamma radiation spots can be quite convenient. Additional spectroscopic features, even with moderate energy resolutions, could provide a useful benefit. As a proof of principle for such a tool, we developed a gamma detector prototype featuring an array of 10 × 10 CsI(Tl) scintillators (1 × 1 × 1 cm3) providing readouts by means of a corresponding array of 6 × 6 mm2 silicon photo multipliers (SiPM). Such a detector table could be easily incorporated into a work desk for quick scanning of possibly radioactive objects. The proposed detector has a good counting efficiency and energy resolution, while the simulations and tests show interesting hot-spot localization capabilities.

Feasibility of polarized laser scattering in detecting the grinding-induced subsurface damage in SiCf/SiC ceramic matrix composite

Given the urgent demand in the effective method for detecting the machining-induced damage (MID) of ceramic matrix composite (CMC). This study first time proposes the polarized laser scattering (PLS) method to detect the grinding-induced damage of silicon carbide fiber reinforced silicon carbide (SiCf/SiC). The feasibility of the PLS detection is demonstrated. Moreover, the sensitivity of PLS detection is found dependent on the radiation spot size of the laser beam. Decreasing the radiation spot size, the sensitivity to MID increases. However, the sensitivity to the pre-existed defects also increases, which would disturb the detection of MID. While increasing the radiation spot size, the intensity of the PLS detection decreases. In this study, when the radiation spot size is 66, 132, or 264 μm, the PLS method is suitable for detecting the grinding-induced damage of SiCf/SiC. This study is important for expanding the detection of the MID of CMC.

Моделювання умов отримання наноструктур в алюмінієвих сплавах при дії іонізуючого випромінювання

The use of laser radiation as a source of ionizing radiation to obtain nanostructured and submicrostructured layers on aluminum alloys requires the determination of the necessary technological parameters. Therefore, a theoretical study of ionizing radiation on aluminum alloy AK8 was conducted according to the previously proposed model. When choosing the region in the material of the aluminum alloy, where nanostructures can be formed under the action of ionizing radiation, apply different lengths of ions. Because of the theoretical study of the formation of nanostructures in the surface layer of the aluminum alloy AK8, the temperature distribution in the zone of ionizing radiation at different depths of the material was obtained. Temperature fields for different heat flux densities q1 = 106 W/m2 and q2 = 105 W/m2 were also constructed. The obtained temperature fields for heat flux q1 showed that with increasing depth of the material, the temperature decreases from 2480 to 650 K. The values of maximum temperatures on the material surface are slightly higher than necessary to obtain nanostructures at lower depths maximum temperatures decrease to nanostructures can be realized. Simultaneously, under the action of heat flux q2 = 105 W/m2, the maximum surface temperature decreased to values of 1950 K, and at depth it was 550 K. and was equal to 106 K/s at q2. All these confirmed the possibility of creating conditions for the formation of nanostructures. Due to the temperature range obtained from the calculated temperature fields, the depths of the aluminum alloy where nanostructures can be formed were determined. Studies of the effect of laser radiation spot size on the surface of the material on the formation of nanostructures were also conducted, which showed that when exposed to a spot size of 3 · 103 to 10-3 m, the possibility of nanostructures is significantly reduced, while reducing the spot size to 10-4 m leads to a significant increase in the possibility of forming nanostructures. To estimate the possible volume of nanostructures, the dependence of the nanocluster size on the heat flux density in the range from 107 to 1010 W / m2 and its action time in the range from 10-9 to 10-3 s were considered. The dependence of the maximum temperature on the heat flux density and the time of its action is also constructed. All this allows you to choose the technological parameters of laser radiation to obtain nanostructured layers on aluminum alloys, and the ability to determine the size of nanostructures allows you to predict the physical and mechanical characteristics of the surface layers of processing materials. These studies may be of interest to specialists in strengthening the surfaces of aluminum alloys and further studies of nanostructures.

Efficient modeling of metal ablation irradiated by femtosecond laser via simplified two-temperature model coupling molecular dynamics

A simplified two-temperature model coupling molecular dynamics (TTM-MD) method is proposed to study the femtosecond laser ablation of metal, which can simulate a micron-sized laser spot irradiation under the premise of atomic-level calculation accuracy. The theoretical TTM-MD model is re-derived using the Langevin equation to reduce the calculation frequency of lattice temperature and improve the solution efficiency. Then, the TTM-MD simulation model is simplified to a one-dimensional model according to the rotational symmetry of laser spot and neglecting the lateral heat transfer. The temperature variation, pressure evolution, and void nucleation are analyzed to reveal the spallation and explosion ablation regimes. The variation of simulated ablation depth with laser fluence is consistent with the experimental results. The full-sized crater profiles predicted by this simplified model also match well with the ablation experiments irradiated by the Gaussian laser spot. Moreover, the step boundary caused by the threshold effect of laser ablation also can be captured on the crater edge. These results suggest that the proposed model provides essential insight into the femtosecond laser ablation by avoiding the limitation of current computing power.

Single-pulse all-optical partial switching in amorphous DyxCo1−x and TbxCo1−x with random anisotropy

Repeated uniform switching of the magnetization of thin films of ferrimagnetic amorphous Gdx(FeCo)1−x in response to single fast laser pulses is well established. Here, we report unusual toggle switching in thin films of sperimagnetic amorphous DyxCo1−x and TbxCo1−x with x ≈ 0.25 irradiated with single 200 fs pulses of 800 nm laser light. The samples have strong local random anisotropy due to the non-S state rare earth. The compensation temperature of the films is ≤180 K, and their Curie temperature is ≈500 K. They are largely switched by the first pulse, and subsequent pulses lead to partial re-switching of a decreasing amount of the irradiated area, with a granular structure of submicrometer regions of switched and unswitched material. Individual switched regions about 700 nm in size are observed around the edge of the irradiated spots where the fluence is at the threshold for switching. Results are discussed in terms of a random anisotropy model where the ratio of local anisotropy to exchange is temperature dependent.

Biological applications of the scanning transmission electron microscope

The STEM has the capability to acquire spatial and chemical information from almost all scattered electrons. Dedicated STEMs do not have any post-specimen lenses but many different detectors instead. The STEM axial bright field mode is quite insensitive to multiple scattering occurring while imaging thick samples such as vitrified whole cells. The blur of small gold sphere has been simulated by Monte Carlo calculations. Direct electron detectors record the rich information of microdiffraction patterns from every irradiated spot while the STEM beam raster-scans over the sample. • The STEM produces distinct images of negatively stained macromolecules (GroEL-ES, top left; antibodies, bottom left). • The STEM produces mass maps of biomolecular assemblies (ClyA; center). • The STEM simultaneously acquires bright (top right) and dark field electron tomograms (bottom right) of thick vitrified samples, allowing heavier elements like phosphorus or calcium to be discriminated from lighter elements like carbon.

Smoldering ignition using a concentrated solar irradiation spot

Ignition of materials by a point source of heating plays an important role in initiating many structure and wildland fires, such as spotting by hot particles, lightning, laser, and concentrated irradiation. Herein, we study the smoldering ignition of tissue paper by a concentrated sunlight spot with heat fluxes up to 780 kW/m2, which is focused by a transparent glass sphere. The diameter of the sunlight spot on the paper sample ranges from 1.5 to 20.0 mm by varying the paper position within the focal length, where a smaller spot has a larger intensity of sunlight irradiation. The measured minimum spot irradiation for smoldering ignition is not a constant and is much higher than 11 kW/m2 measured in a traditional cone-calorimeter test. As the diameter of the irradiation spot decreases from 20 to 1.5 mm, the minimum irradiation for smoldering ignition increases from 17.5 to 205 kW/m2, and the ignition energy increases from 0.084 to 2.0 MJ/m2. A simplified heat transfer analysis reveals that the lateral conductive cooling within the fuel becomes dominant for a smaller spot ignition area. This work ultimately quantifies the potential fire risk from concentrated sunlight spots and helps elucidate the underlying mechanisms leading to smoldering ignition.

Assessment of ablation damage on quartz ceramics through experiment and 3D modelling considering a dynamic heat source

The effects of irradiation time (IT), laser power (LP), and spot diameter (SD) on the damage caused to quartz ceramics under continuous-wave laser irradiation were investigated through an orthogonal experiment. The experimental results show that the LP has the dominant effect on the depth of an ablation pit, while the SD has the greatest impact on the diameter of the ablation centre. The diameter and depth of the ablation pit were both positively correlated to the irradiation energy. The bubbles and molten silica transition layer affected the laser beam's reflection and transmission properties, leading to the incident laser beam scattering into the entire ablation pit and forming an elliptical ablation pit. Furthermore, a 3D finite element (FE) model considering a dynamic heat source was developed to simulate the laser damage process. The shape and dimension of the ablation pit predicted by the FE model were consistent with those obtained through the experiment, demonstrating the effectiveness and rationality of the model. The FE analysis results show that the different ablation rates in the radial and depth directions significantly influence the morphology of the ablation pits. The temperature gradient in the transition region increases while the thickness of the transition region decreases as the LP increases. This indicates that a large LP will lead to greater thermal stress in this area and result in more microcracks.

Optimization of two-beam laser cleavage of silicate glass

Subject of study. The values of technological parameters ensuring the effective two-beam laser cleavage of silicate glasses are determined in this study based on numerical modeling. Method. Multi-objective optimization of two-beam laser cleavage of glass plates is performed using the multi-objective genetic algorithm (MOGA) implemented in the DesignXplorer module of Ansys Workbench software. Main results. The temperatures and thermoelastic stresses are calculated using the finite element method in a quasistatic setting within the uncoupled thermoelasticity problem using the Ansys Parametric Design Language. A regression model of two-beam laser cutting of glass is obtained using a face-centered variant of the central composite design of the experiment. The machining speed, the power of a laser with a wavelength of 10.6 µm, the radius of the radiation spot of the beam with a wavelength of 10.6 µm, the power of a laser with a wavelength of 1.06 µm, and the radius of the radiation spot of the beam with a wavelength of 1.06 µm are used as the variable factors. The maximum temperatures and tensile stress values in the laser machining area are used as the responses. The regression model is tested on a test dataset. The obtained results indicate that the regression model is consistent with the finite element analysis data. The effect of the technological parameters of machining on the maximum values of temperature and tensile stress in the laser machining area is evaluated. We establish that the machining speed and the parameters of the laser beam with a wavelength of 10.6 µm have the biggest effect on the maximum temperatures, whereas all the variable factors have a significant effect on the maximum values of tensile stress. Two-beam laser cleavage of glass is optimized for two variants of the problem setting: either using the criterion of the maximum tensile stress or the criteria of the maximum tensile stress and machining speed. The parameters obtained after optimization and through finite element modeling were compared. The maximum relative error of the results obtained using the MOGA do not exceed 5% for the determination of maximum temperatures and 9% for the determination of the maximum values of thermoelastic stress in the area of the laser machining. Practical significance. The machining parameters that ensure significant increase in the productivity and reliability of two-beam laser cutting when applied in practice are determined using modeling.

Detached regime with highly radiating X‐point: Physics and modelling

AbstractA possibility to operate with fully detached targets and highly radiating X‐point was recently demonstrated on ASDEX Upgrade, JET, and DIII‐D with intensive impurity seeding (N, Ne, Ar) and feedback control. Notable feature of such a regime is the radiated power fraction of up to 90% of discharge power inside the separatrix without a confinement degradation, or even with confinement improvement (in terms of H‐factor), which leads to a full detachment of both targets. Therefore, this regime might be attractive for the next generation reactor scale tokamaks like DEMO or CFETR, where most of the power should be radiated. In the present report, the recent achievements in the understanding of such regime are reviewed. The effectiveness of divertor target shielding by different impurity gases is discussed, paying attention to its first ionization potential. SOLPS‐ITER modelling results illustrating the impurity flow pattern are presented, and the importance of drift flows is demonstrated. The effect of the machine size on the effectiveness of the divertor shielding by impurity radiation is discussed. It is demonstrated that in bigger machines impurity radiation is better kept in the divertor and divertor asymmetry is less pronounced. As the seeding rate increases, both targets fully detach, and neutrals start to penetrate inside the separatrix above the X‐point, leading to the plasma cooling there and to the formation of an observable localized radiation spot in the X‐point vicinity. The cold zone above the X‐point thus behaves as an energy sink like a divertor in conventional regime, so that the perpendicular decay length of perpendicular turbulent energy flow appears to be of the order of of conventional divertor. During the formation of the radiating X‐point a potential hill/well (depending on the direction of drift) is formed on perturbed closed flux surfaces, and the corresponding drift vortex fluxes appear to give major contribution to the particle balance. SOLPS‐ITER simulations show that the radial electric field significantly deviates from neoclassical formula and may even change sign (become positive). Thus, the zone of maximal poloidal rotation shear may shift inwards, which might be responsible for the inward shift of the transport barrier and for the confinement improvement. This effect is different to the discussed extension of peeling‐ballooning stability boundary by intensive impurity injection, which might explain experimentally observed ELMs suppression or their frequency reduction.

Femtosecond Laser-Based Additive Manufacturing: Current Status and Perspectives

The ever-growing interest in additive manufacturing (AM) is evidenced by its extensive utilisation to manufacture a broad spectrum of products across a range of industries such as defence, medical, aerospace, automotive, and electronics. Today, most laser-based AM is carried out by employing continuous-wave (CW) and long-pulsed lasers. The CW and long-pulsed lasers have the downside in that the thermal energy imparted by the laser diffuses around the irradiated spot and often leads to the creation of heat-affected zones (HAZs). Heat-affected zones may degrade the material strength by producing micro-cracks, porous structures and residual stresses. To address these issues, currently, attempts are being made to employ ultrafast laser sources, such as femtosecond (fs) lasers, in AM processes. Femtosecond lasers with pulse durations in the order of 10−15 s limit the destructive laser–material interaction and, thus, minimise the probability of the HAZs. This review summarises the current advancements in the field of femtosecond laser-based AM of metals and alloys. It also reports on the comparison of CW laser, nanosecond (ns)/picosecond (ps) lasers with fs laser-based AM in the context of heat-affected zones, substrate damage, microstructural changes and thermomechanical properties. To shed light on the principal mechanisms ruling the manufacturing processes, numerical predictions are discussed and compared with the experimental results. To the best of the authors’ knowledge, this review is the first of its kind to encompass the current status, challenges and opportunities of employing fs lasers in additive manufacturing.

Ultrashort pulsed laser induced complex surface structures generated by tailoring the melt hydrodynamics

We present a novel approach for tailoring the laser induced surface topography upon femtosecond-fs pulsed laser irradiation. The method employs spatially controlled double fs laser pulses to actively regulate the hydrodynamic microfluidic motion of the melted layer that gives rise to the structures formation. The pulse train used, in particular, consists of a previously unexplored spatiotemporal intensity combination including one pulse with Gaussian and another with periodically modulated intensity distribution created by Direct Laser Interference Patterning (DLIP). The interpulse delay is appropriately chosen to reveal the contribution of the microfluidic melt flow, while it is found that the sequence of the Gaussian and DLIP pulses remarkably influences the surface profile attained. Results also demonstrate that both the spatial intensity of the double pulse and the effective number of pulses per irradiation spot can further be modulated to control the formation of complex surface morphologies. The underlying physical processes behind the complex patterns generation were interpreted in terms of a multiscale model combining electrodynamic excitation with melt hydrodynamics. We believe that this work can constitute a significant step forward towards producing laser induced surface structures on demand by tailoring the melt microfluidic phenomena.

A single long electron bunch detect electromagnetic field evolution in laser plasma

Laser fusion research needs much more high-time-resolved diagnostic technologies to study the dynamic process in laser plasma. We develop a special method and setup a device to measure the electromagnetic field in the plasma by using a single electron bunch. The measurement covers the whole-time window of the plasma process driven by a 3.6 ns laser pulse. An electron source can generate a single electron bunch with 0–100 keV energy and 10ns bunch length. A laser pulse with 1 J energy and 532 nm wavelength irradiates on the edge of a silver target, the target nearby the irradiated spot is ionized into plasma. At the beginning of plasma generation, the head of the electron beam begins to pass through the plasma. Electromagnetic field in plasma pushes the electrons transversely. A high voltage pulse at a good time is used to deflect the electrons linearly in the transverse direction to avoid overlapping of the different electrons on the scintillator downstream. By analyzing the deflection distances of the different electrons in this single bunch, we succesfully achieve an average electronic field along the trajectory in the plasma in the whole plasma process. The maximum value of this electronic field is <inline-formula> <tex-math id="M2">\begin{document}$ 7.74\times {10}^{5}\;\mathrm{V}/\mathrm{m} $\end{document}</tex-math> <alternatives> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20211374_M2.jpg"/> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20211374_M2.png"/> </alternatives> </inline-formula>.

Directed changing properties of amorphous and nanostructured metal alloys with help of nanosecond laser impulses

One of the most important problems of materials science is the ability to control the physical and mechanical properties of materials that differ in structure. Forming a specific structure on the surface is a time-consuming process, especially for non-standard alloys. Such materials include amorphous and nanostructured metal alloys. In practice, their use is possible after heat treatment. Additional processing often leads to the destruction of the nanostructure. The laser impulse has a number of features, including a complex effect on the surface layers of the material. The wide variable possibilities of laser processing provide the basis for the possibility of forming the mechanical properties of amorphous-nanocrystalline metal alloys. Spot irradiation with high-energy beams can preserve the unique physical properties of the samples as a whole and improve the strength characteristics. The directed change in the properties of an amorphous-nanocrystalline metal alloy by local processing with a nanosecond laser impulse is an urgent research task. This work was carried out with financial support by International Information Nobel Centre.

Heat transfer simulation in laser irradiated retinal tissues

A realistic model of human retinal tissues to simulate thermal performance of optical laser photocoagulation therapy is presented. The key criteria to validate the treatment effectiveness is to ensure the photocoagulation temperature between 60 and 70 °C is reached in the treatment region of interest. The model presented consists of truncated volumes of the retinal pigment epithelium (RPE) and adjacent retinal tissues. Two cases of choroid pigmentation are modelled to signify extreme cases of human eye difference: albino and dark colour choroid pigmentation. Conditions for consistent heating over the irradiated treatment spot is modelled for laser beams with different intensity profiles: ‘top-hat’, Gaussian and ‘donut’ modes. The simulation considers both uniform heating within retinal tissue layers and spatial intensity decay due to absorption along the direction of laser propagation. For a 500 μm spot, pulse length 100 ms and incident power to the cornea of 200 mW, realistic spatial variation in heating results in peak temperatures increasing within the RPE and shifting towards the choroid in the case of choroidal pigmentation. Finite element analysis methodology, where heat transfer theory governs the temperature evolution throughout tissues peripheral to the irradiated RPE is used to determine the zone of therapeutic benefit. While a TEM01 donut mode beam produces lower peak temperatures in the RPE for a given incident laser power, it reduces the volume of retinal tissue reaching excessive temperatures and maximises the zone of therapeutic benefit. Described are simulation limitations, boundary conditions, grid size and mesh growth factor required for realistic simulation.

Alkaloids as Photosensitisers for the Inactivation of Bacteria.

Antimicrobial photodynamic therapy has emerged as a powerful approach to tackle microbial infections. Photodynamic therapy utilises a photosensitiser, light, and oxygen to generate singlet oxygen and/or reactive oxygen species in an irradiated tissue spot, which subsequently react with nearby biomolecules and destroy the cellular environment. Due to the possibility to irradiate in a very precise location, it can be used to eradicate bacteria, fungus, and parasites upon light activation of the photosensitiser. In this regard, natural products are low-cost molecules capable of being obtained in large quantities, and some of them can be used as photosensitisers. Alkaloids are the largest family among natural products and include molecules with a basic nature and aromatic rings. For this study, we collected the naturally occurring alkaloids used to treat microorganism infections using a photodynamic inactivation approach. We gathered their main photophysical properties (excitation/emission wavelengths, quantum yields, and oxygen quantum yield) which characterise the ability to efficiently photosensitise. In addition, we described the antibacterial activity of alkaloids upon irradiation and the mechanisms involved in the microorganism killing. This review will serve as a reference source to obtain the main information on alkaloids used in antimicrobial photodynamic therapy.

Analysing the distribution of runaway electrons in the EAST tokamak based on SOFT

In the Experimental Advanced Superconducting Tokamak (EAST), the energy of runaway electrons confined in plasma can reach tens of MeV. These electrons can emit synchrotron radiation and, in turn, their distribution can be obtained by synchrotron radiation. The Synchrotron-detecting Orbit Following Toolkit (SOFT) can simulate synchrotron radiation images with different runaway electron distributions. In these simulations, one initially assumes that the runaway electrons are mono-energetic, then obtains the distribution of the electron pitch angle θp with respect to the magnetic field, which is then employed to analyze the energy distributions of runaway electrons. In this way, one evaluates whether the simulation results are in agreement with experimental results concerning the synchrotron radiation spot shape and the intensity variations within the spot. Upon analyzing synchrotron radiation with optimal runaway electron distribution, we find that the peak value of synchrotron radiation appears near θp=0.3 rad, which is larger than θp of most runaway electrons.

Study on impulse and ablation of aluminum irradiated by millimeter spot of short pulse laser

Aluminum is a high performance working medium for laser ablation micro propulsion. In order to study the propulsion performance and ablation of aluminum under millimeter light spot irradiation, a short pulse Nd: YAG laser with wavelength of 1064nm and pulse width of 8NS was used to irradiate aluminum target in atmosphere. The impulse, the impulse coupling coefficient and the ablation morphology of the aluminum target produced by 6 kinds of millimeter-level light spots are measured. The experimental results show that when the spot diameter reaches 6-7mm, the increasing trend of impulse and impulse coupling coefficient of aluminum target with the increase of laser energy slows down; A large number of ablation products began to accumulate on the surface of the target pit.

Food 3D Printing with Starch Suspension

: 3D food printing is a method of making a novel three-dimensional processed food based on digital data by applying additive manufacturing technology to food materials [1]. Food 3D printers are expected to serve foods with controlling nutrients and textures suitable for an individual's health. There are many different types of food 3D printers such as screw type, syringe type, inkjet type, etc. But there are few 3D printers capable of printing hard textured foods. We aim to develop a food 3D printer capable of printing hard textured food with starch suspension [2]. In the printing process, the starch suspension is irradiated with a blue laser, and irradiated spot is gelatinized by heat generated by photothermal conversion. Experiments: The Food 3D printer is based on a commercially available 3D printer Geetech i3 pro B. The extruder unit of Geetech i3 pro B is replaced by a blue laser (wavelength 450 nm) module (alfawise 5500mm ). The maximum laser output is 5.5W. We select a visible blue laser that is common and safe. As the first experiment, We print a pyramid shape (shown in Fig.1) using starch suspension as a printing material. The pyramid has composed of five layers and the thickness of each layer is 0.5 mm. The bottom layer is a 10mm square and the higher layer has shorter edges. Fig.2 shows a schematic diagram of the modeling method. The starch suspension (50 % wt in water) is poured (added) into the container and leveled to make 0.5mm thickness. The liquid surface of the Suspension is irradiated with laser and gelatinized. 3D printing is performed by repeating those processes. Tartrazine (0.03% wt) is added for enhancing the absorption of the blue laser. The laser scan speed is set at 5.0 mm/s. Results: Fig.3 shows a Photo of the 3D printed pyramid structure. We successfully 3D printed pyramid structure with starch suspension. The 3D printed pyramid structure is larger than the original pyramid 3D data. We assume that the gelatinized starch absorbed water and swelled during and after the 3d printing process.