Additive Manufacturing (AM) is an emerging part production technology that offers many advantages such as high degree of customization, material savings and design of 3D highly complex structures. However, AM is a complex multiphysics process. Therefore, only a limited number of materials can already be commercially used to produce parts and a handful of others are being studied or developed for such process. Consequently, limited knowledge on this process is available, especially concerning materials that present thermomechanical challenges such as brittle materials.
The research I did during my PhD studies focuses on additive fabrication of silicon pillars on a monocrystalline silicon wafer by Direct Laser Melting (DLM) with a pulsed 1064 nm laser beam. The simple geometry of pillars allowed for the first determining steps into process understanding. Several results were achieved through this PhD work. First, crack-free silicon pillars were successfully built onto monocrystalline silicon wafers. With the help of in-situ process monitoring and sample characterization, wafer substrate temperature and laser repetition rate were found to be the main influential parameters to obtain crack-free samples, as minimum substrate temperature of 730°C and a minimum repetition rate of 100 Hz were necessary to reach this goal (for a feed rate of 15 g/min and a pulse duration of 1 ms). The influence of secondary process parameters such as feed rate and energy per pulse were also discussed. A simple Finite Element Modeling (FEM) model validated by the experiments was used to explain crack propagation in the samples. Then, process monitoring of the DLM process was realized. High-speed camera image analysis re-vealed that vertical stage speed and powder feed rate should match to obtain a constant pillar building rate. As all pillars presented necking at their base, estimations of the thermal characteristics of the pillar during growth were carried out by FEM simulations. They were additionally used to explain the pillar final shape. Finally, the microstructure of the pillars built was characterized by the Electron Back-Scattering Dif-fraction (EBSD) technique. In the conditions presented in this work, the microstructure of the pillar was found to be in the columnar growth mode. The feed rate was identified as the most influential parameter on the microstructure, followed by the stage speed, the impurity content of the powder and the crystallographic orientation of the substrate. Epitaxial growth was achieved on more than 1 mm with a feed rate of 1.0 g/min, a stage speed of 0.1 mm/s, a powder with purity of 4N and a <111> oriented wafer substrate. This work could be further continued by making improvements to the DLM setup, studying the influence of additional process parameters on the thermomechanical behavior and the microstructure control of the pillars, and/or using these results to realize more complicated shapes, either with this setup or by using a powder bed technique.
About
I was born in France and I have grown up in a little town called Beynes, in the department Yvelines, no so far from Paris and Versailles. I am the first of four kids! As a child, I wanted to be a journalist. I have always been interested in digging up into a subject in order to transforming into articles that could be read by others. I had a few friends writing a bunch of articles alongside so we could turn everything into magazines. I spent a lot of time playing with a - now old - layout software in order to make this publication look like my favorite magazines at that time – L’Hebdo, le monde des ados. I even managed to get an internship for a week there!
About
I was born in France and I have grown up in a little town called Beynes, in the department Yvelines, no so far from Paris and Versailles. I am the first of four kids! As a child, I wanted to be a journalist. I have always been interested in digging up into a subject in order to transforming into articles that could be read by others. I had a few friends writing a bunch of articles alongside so we could turn everything into magazines. I spent a lot of time playing with a - now old - layout software in order to make this publication look like my favorite magazines at that time – L’Hebdo, le monde des ados. I even managed to get an internship for a week there!
Ergane
a textile pattern project
Fashion is a powerful communication tool : it gets a lot of media coverage and is expressed in our everyday life. Therefore, this project uses fashion as a communication tool to promote cross-overs between science and design, as well as the importance of sustainable values. The prints are designed as an eye-catcher and a converstaion starter to promote curiosity on scientific topics and other subjects related to nature. The inspiration for the prints are communicated to the customer with references and small stories linked to the topic. We hope to inspire our customers through unique and beautiful print designs that have a meaning and inspiration that they can share with others. Here is a selection of the prints we developed so far.
Ergane also has an Instagram account:
Abysses
I find the abysses particularly mysterious and fascinating, that is why I wanted it to be the topic of my first print! As I didn’t know so much about it, I did a bit of research and selected some creatures to mix up in a print! Here they are:
🐠 The tripodfish is almost blind (but at 6000 m below the ocean, there is probably not so much light^^). His reaaaallly long fins allow him to “sit” at the bottom of the ocean and feel vibrations created by creatures moving in the sands. It is hermaphroditic too, which means it produce both the gametes of a male and a female. Here is a cool video of a tripodfish: https://www.youtube.com/watch?v=yOKdog8zbXw
⭐️ The common Brittle Star is closely related to the starfish family. Some species can be found up to 8000m below the surface of the ocean!
🐠 The Rhinochimaeridae, whose nose reminds of a Rhino. His long appendicle allows him to localize little fishes that he eats. It can be found at up to 2000m below the ocean’s surface. Here is a super cool video of a swimming Rhinochimaeridae: https://www.youtube.com/watch?v=L_QJ8oHsfkM
🐙 The dumbo octopus: the cutest octopus ever but quite rare 😊 He lives between 1000 and 4000 m depth, and maybe even deeper. Here is a nice video of a dumbo octopus: https://www.youtube.com/watch?v=pl4pqu5FTaI
I drew them with watersoluble graphite pencils from Caran d’Ache :)
ice age
This print is a tribute to some extinct Ice Age animals. There are several possible explanations for the disappearance of the giant mammals that lived during the Ice Age. For some, climate change is responsible. This is the case, for example, for the furry rhinoceros, which could not adapt to warmer temperatures, nor migrate to a habitat more favorable to its survival. For others, human migration to more and more ecosystems may have also precipitated some changes, this could be the case for the mammoth for example, which was largely hunted by humans. But this is probably due to a mixture of the two. Some have survived, like the deer. In any case, I find it fascinating that we can still find whole bodies of these animals preserved in the ice for several tens of thousands of years, like Lyuba, the baby mammoth. We won't be able to see them in real life (well, okay, some of them were probably really scary!), so here is a little cocktail of some of them gathered on this print: the saber-toothed tiger, the mammoth, the megaceros deer (its antlers) and the beautiful armadillo (Dasypus Bellus, from the patterns of its skin).
To create this print, I first drew some of the animals with pencils. Using scans of these drawings, I drew the animals digitally, then arranged them to create this pattern.
Bats
Bats are such cool animals! They use echolocation to map their surroundings at night, meaning that they can emit sounds which will then « bounce » on elements of the environment and return under the form of an echo into their ears. By emitting sounds of different frequency, bats can detect elements of different sizes, shapes and at different distances.
There is a cool video on this mechanism:
https://youtu.be/laeE4icRYp4
This print was created with watercolors on paper then scanned and edited in Photoshop.
Cryo-genius
Do you know the Rana Sylvetica, the wood frog? This frog, which lives mainly in the forests of the USA and Canada, allows its vital functions to freeze almost completely during the winter season. Thanks to a storage system of glucose and urea, among other things, it avoids the degradation of its cells when freezing and thawing in spring, and can thus survive temperatures down to -18°C! When I learned of their existence, I was fascinated, and decided to dedicate a print to them by drawing frogs in ice cubes!
https://www.maxisciences.com/grenouille/ces-extraordinaires-grenouilles-qui-gelent-en-hiver_art32442.html
To create this print, I first painted each frog individually in its ice cube with blue ink. I then scanned my drawings and arranged them to create the final design! I loved the blue, which reminded me of the cold of winter, but is also a rather calm color, like those frogs patiently waiting for the warm weather!
states of water
Ah, water! So vital and essential and at the same time so much a part of our lives that we forget how scarce it can be in some parts of the world. Did you know that water is one of the few compounds that takes up more space in solid form than in liquid form? I'm sure you've left a bottle of water to cool in the freezer thinking you wouldn't forget it, only to find it a few hours later, completely exploded! This is because the water molecule is made up of one oxygen atom and two hydrogen atoms. Oxygen is negatively charged while hydrogen is positively charged. The molecule is therefore polarised, and can form hydrogen bonds between the oxygen in one molecule and the hydrogen in a neighbouring molecule. When the temperature is below 0°C, the molecules arrange themselves in hexagons to take these hydrogen bonds into account, which does not really optimise the arrangement of the molecules in the ice structure. It therefore takes up more space! This printout is inspired by the molecular structures of water in each of its states, starting with the solid state, then the liquid state where the molecules are no longer arranged in crystals and finally the gaseous state where they are much further apart!
https://www.chemtube3d.com/ss-ice/
I created this print only on the computer, using images of the molecular structure of ice. After trying several colour combinations, I decided on pink, red and light yellow. I love the contrast between the coldness of ice and the warmth of these colours!
