Exploration and Analysis of Ceramic Fabrication and Computation Using Material Extrusion and Robotic Additive Manufacturing

By Jasmin Singh

Introduction

[Fig. 1] New Bedford Research and Robotics’ additive manufacturing robot.

Ceramic is a material that is gaining traction in various industries, including electronics, energy, machinery, and biotechnology. Its strength and resistance to high temperatures make it an ideal material for creating functional parts with intricate structures that are difficult to manufacture using conventional techniques. This opens up a vast range of potential use-cases for ceramic additive manufacturing technology. In the biomedical field, clay materials are already widely used for applications such as artificial bones, joints, and teeth.

The purpose of this research is to learn how we might support human contribution and artistic creation, not to undermine either. With material extrusion and robotic additive manufacturing, it is possible to explore the possibilities of creating more complex structures based on a variety of materials and with more precision and accuracy than human-made structures. There are active attempts to produce structures that go beyond simple shape production, pushing the boundaries of what is possible with 3D printing technology.

The range of media that can be used for additive manufacturing is expanding rapidly, driven by the increasing range of applications and the need for more sustainable and efficient manufacturing methods. As a result, there is immense potential for innovation and progress in the field of ceramic additive manufacturing.

Methods

As an undergraduate researcher, I collaborated with a team of researchers to determine key parameters for 3D printing with clay, collecting valuable data to gain insight into its operation and allowing for a comprehensive analysis of its respective properties and applications. The following variables were the subject of our study: frequency or flow rate (measured in hertz), the speed at which clay is extruded; nozzle size (measured in millimeters), the diameter of the nozzle used to extrude the material; and layer height (measured in millimeters), the fixed height for each extruded layer. During our investigation, our research team was unable to establish certain critical variables, such as the moisture level of the clay.

Early research into clay additive manufacturing involved developing experimental designs to evaluate bridging and overhang to see how designs printed with clay are executed and how they support their weight.

[Fig. 2a, 2b] Design created by Jack Kertscher entitled Overhang Test I, one of many

designs to test overhang in ceramic additive manufacturing. Printed with a frequency of 468Hz, layer height of 1mm, nozzle size of 3mm, machine speed at 40%. Overhang failed at approximately 15mm.

Bridging refers to segments in additive manufacturing where the extruder distributes material over the air between two supported points in the same layer as the bridge. This eliminates the need for support beneath the bridge.

Overhangs are unbalanced slopes caused by 3D printing’s usual layer-by-layer method–when a layer reaches the bottom of a slope, each succeeding layer must extend slightly beyond the layer before it, sometimes causing a disproportionate distribution of weight that causes the slope to hang.

Variables such as frequency, nozzle size, layer height, and machine speed can affect these parameters.

Contributions

Ensuring the printed clay structure could support its own weight came up frequently during our research. I focused on designing structures that could maintain their own weight without the use of external or supplementary supports. To examine weight distribution, I created experimental designs dependent on twisted constructions. These prints supported their weight without trouble both during and after printing.

[Fig. 3a, 3b] Design created by Jasmin Singh entitled TwistExpUpd, a twisted structure printed with a frequency of 308Hz, layer height of 1mm, nozzle size of 3mm, machine speed at 40%.

Proceeding with this design, I created a closed, twisted dome structure that can support its weight. At the time that this summary is written, there is no record of a closed dome shape printed with ceramic. I will continue studying with this particular design as a result. A larger print of this design, roughly 1 foot by 1 foot in size, will be made in order to assess the weight distribution and capped structures on a larger scale.

[Fig. 4a, 4b] Multiple prints of design created by Jasmin Singh entitled TallTwistDome, a twisted and closed dome structure. TallTwistDome (rightmost) printed with a frequency of 298Hz, layer height of 1mm, nozzle size of 3mm, machine speed at 40%. TallTwistDome2 (second from left) printed with a frequency of 198Hz, layer height of 0.5mm, nozzle size of 3mm, machine speed at 40%. TallTwistDome4 (leftmost) printed with a frequency of 248, layer height of 0.7mm, nozzle size of 3mm, machine speed at 40%. Observe the gaps within each layer within the print caused by a relation between layer height and frequency.

Conclusion

Ceramic additive manufacturing focuses on the use of advanced technology to create structures with precision and intricacy that standard manufacturing processes may struggle to achieve. As the field continues to evolve, we can anticipate breakthroughs and solutions that will reshape industries and contribute to a more sustainable and adaptable manufacturing landscape. Furthermore, we can expect an increased integration of ceramic additive manufacturing into mainstream production methods.

Our primary objective revolves around identifying variable correlations in order to establish a comprehensive standard operating procedure (SOP) tailored for ceramic additive manufacturing. Concurrently, our research efforts persist as we work towards preparing a comprehensive research paper that will thoroughly document our discoveries.

As we learn more about the principles of clay additive manufacturing, we will be able to effectively apply this knowledge to various use cases, allowing for the optimal design execution.

A Step Forward: Unraveling the Mental Health Tapestry of Students from the African Diaspora

By Olivia Munyambu

This study aimed to uncover how Black students coped with various stressors and the effects these coping strategies had on their lives. Mental health is presented as fundamental to an individual’s overall well-being. The study described mental wellness as an intersection of emotional well-being with functional aspects like relationships, personal control, and purpose in life. It also underscored the tight-knit relationship between physical and mental health.

The research adopted an indigenous wholistic theory, integrating elements of Afrofuturism and Decolonization theories to structure focus group sessions. Content analysis was employed to examine data collected during these sessions. The participants included undergraduate students who identified as Black or African American. Recruitment involved advertising across campus and through local multicultural clubs. Participants received incentives like Amazon gift cards, and their informed consent was obtained.

A sample of an ad for Olivia Munyambu’s focus groups

The results of this study could open the door for conversations and policy changes directed at making the university campus a more welcoming and supporting space for Black students. I focused primarily on mental health but remained open to any other health matters that may arise in discussion. Another goal was to learn more about if, and how, Black students come together to cope. I intended for the results of this research to spark an increased interest on the part of the faculty, student affairs (including but not limited to the counseling center), and the university administration towards developing and implementing effective methods, policies, and campus climate changes that will more effectively address mental health in a way that tailors to the unique experiences of Black students. I believe that in doing this, the university campus can become a welcoming place for students of the African Diaspora to express their mental health concerns without being demonized and harmed in their pursuit of wellness in a country that was designed to oppress them, and in which the oppressive mechanisms still persist today.

Participating in this study was an enlightening experience. Addressing student stressors is vital, and I’m glad to have contributed in some small way. The team took privacy and confidentiality seriously, which made the environment feel safe for sharing. Now, I eagerly await the outcomes and insights that this research will bring to light. I thank the Office of Undergraduate Research for giving me the opportunity to conclude this important portion of my research project.

Presentation at the National Hydropower Association’s Waterpower Week in Washington D.C. 

Group photo 

We worked with Professors Daniel G. MacDonald and Mehdi Raessi to participate in the Marine Renewable Energy Collegiate Competition, which was held as part of the Waterpower Week (https://waterpowerweek.com/) in Washington D.C. in May 2023. Although we were not giving a formal poster or talk at the conference, we presented twice, the first was a business plan pitch, and the second was an outreach presentation, as well as presenting a poster, all as part of the competition. This travel was partially funded by the OUR, the US Department of Energy, and the National Renewable Energy Laboratory. We appreciate all the supports we received to present our work at the national level.

The Marine Energy Collegiate Competition (MECC) in Washington DC presented a pivotal platform to highlight our proficiency and commitment to Science, Technology, Engineering, and Mathematics (STEM) education. Our team participated in the Marine Energy Collegiate Competition (MECC) with the aim of showcasing and advancing our innovative technology that converts wave energy into usable electrical power.

Snapshots from the presentations

Our vision for a clean energy future is rooted in harnessing the inherent power of natural elements to generate sustainable electrical energy, fueling technological advancements. As we continue to push the boundaries of technology, it’s crucial that we minimize our environmental impact and reduce our carbon footprint. By tapping into the wealth of natural energy resources, we aim to unlock the next generation of technologies that allow us to coexist harmoniously with our environment.

Our project, the Maximal Asymmetric Drag Energy Converter (MADWEC), employs a ballast system and an underwater subsystem to create drag. This powers the mechanical Power Take-Off (PTO) system, converting wave energy into electrical energy that can be stored, offering a clean and sustainable way to harness wave energy.

Progress Report on the Creation of a Microfluidic Device for the detection and Characterization of Exosomes

By Ken-Lee Sterling

Collaborators: Michael Nessralla, Vinh Phan, Jenny E Luo Yau and Prof. Milana Vasudev

Portrait of Ken-Lee Sterling at work in his lab. 

Introduction

During the last few decades fatal illnesses such as cancer seem to have become more prevalent in undeveloped as well as developed societies. The tools at our disposal to fight these diseases have become increasingly vast (endnote 1). However, detection and prevention are much more beneficial and productive than attempting to combat the cancerous cells. This leads to the question of if a pre-cancerous formation could be detected before it reaches the point of needed invasive combat stage.

Figure 1. Exosome structure and origin

Through the development and creation of a Microfluidic device with an implanted SERS detector it could be possible to present the exosomes to the embedded sensor for real-time characterization and detection. This could theoretically be a less expensive and affordable method of cancer detection and prevention. If the microfluidic device is easy to make and repeatable to a high degree, that will allow testing with more accuracy and less variation. When an appropriate outlet design and channel shape are incorporated, then the particles can be captured with high purity, high yield, and at a high rate concerning the concentration of the solution. This allows for downstream analysis, which in this project correlates to a SERS sensor (endnotes 2,3) which will be used to analyze the particle.
A microfluidic chip is a pattern of molded or engraved microchannels/ pathways. The network of microchannels can be connected and incorporated into a macro environment4. Microfluidic devices use the unique physical and chemical properties of liquids and gasses at the micro and nano scale. The most studied way to control the fluids is the use of custom shaped and directed micro channels5. Channel shapes can focus, concentrate, order, separate, transfer, and mix the particles and fluids (endnotes 5,6).

Figure 2. Descriptive images of different types of cellular vehicles

Exosomes, otherwise known as extracellular vehicles (EVs) are classified into three groups based on their size and biogenesis (footnote 7). Exosomes range from (30-200nm) to micro vesicles (100-1000) and apoptotic bodies (>1000nm) (Fig 2) (endnotes 8, 9). Exosomes are of endocytic origin (3,1), which means that they arise from the intake of material into the cell through the folding and subsequent encapsulation of the lipid membrane around the materials (Fig 1).7 EVs can be further categorized based on their density, composition, and function. EVs are membrane-bound due to their nature of being carriers of cell-cell communication. They take on a spherical shape and consist of proteins such as CD9, CD63, and CD81, which are part of the Tetraspanin family and cytoskeletal components. These vesicles, once secreted can provide key information from the cell of origin, like a “cell biopsy.”

Figure 3. Effect of Channel Shape and Size on particle movement

To understand the device, the physics that drive the device must be understood. Microfluidic devices use the unique chemical and physical properties of liquids and gasses at the micro and nano scale (endnote 5). The most studied way to control the fluids is using shaped channels. Channel shapes can focus, concentrate, order, separate, transfer, and mix the particles and fluids (endnote 6). A deviation from a straight channel introduces dominant/weaker lift forces and internal lift through the interaction with the particle and the adjacent wall (Fig 3). Focusing the particles and fluid into specific shapes and channels allows the particles to self-sort and filter. Using a square channel as an example, randomly dispersed particles of a certain size will focus on four symmetric equilibrium positions near the center of the channel wall face (Fig 4 a). When an appropriate outlet design and channel shape are incorporated, then the particles can be captured with high purity, high yield, and at a high rate concerning the concentration of the solution. This allows for downstream analysis, which in this project correlates to a SERS sensor (endnote 10). The SERS sensor will be used to analyze the particles.

Figure 4.a. Particle orientation within a square tube on indeterminate length

The ultimate objective of the entire apparatus is to seamlessly integrate a Surface Enhanced Raman Sensor (SERS) into the microfluidic device and enable the fluid to flow through the sensor, thus facilitating the identification of exosomes. A reservoir will hold a solution of PBS buffer and 1% Bovine, in which the exosomes will be suspended. Using a connected pump, the fluid will flow from the reservoir through the microfluidic device and get filtered before passing in front of the SERS sensor, which will help detect the exosomes. This will allow the detection of Ovarian Cancer exosomes, which can confirm or deny a diagnosis of ovarian cancer in a woman. Early diagnosis is essential for finding cancer cells. The traditional and current methods (diagnostic magnetic resonance imaging (MRI) and computed tomography (CT) are typically highly costly and come with several downsides. A high dosage of radiation in the long term can cause damage to healthy cells and may cause serious issues for the patient depending on the cells that are affected or not. The device is a rapid, non-invasive method that will allow for rapid cancer diagnosis. Notably, the device will have characteristics that improve on similar devices in the category, which are discussed in length below.

Methods/ Technical Approaches

During the initial discussions of the PDMS casting, the consensus was that different PDMS to curing agent ratios had to be synthesized to determine which ratio would yield the best overall results. Calculations were done to determine the proper breakdown of the PDMS to curing agent ratio. The initial casting dimensions were based on version 15 of the solid works models (Fig.4.b). The proper breakdown of the ratios was calculated through the simple equation of .Where the being the total internal volume of version 15 of Solid Works model. is the total number of parts. The total internal volume of version 15 of the PDMS mold was calculated to be 3.4 mL.

Figure 4.b. Version 15 of the microfluidic device

With the z-height being 0.5 cm, the x-height being 3.4 cm, and the y-height being 2.00 cm, resulting in a total volume of 3.4 cm3 or 3.4 mL. It was decided that the ratios that would be tested and cast would be 10:1 and 15:1. The total amounts of the required volumes for both the 10:1 and 15:1 were calculated using the equation previously mentioned. For the 10:1 and 15:1 casting, there was an assumed 0.1 mL margin of error for the castings and potential residue material that would be left behind from mixing the PDMS/Curing agent to the transfer into the models. The calculations for the 15:1 casting proceeded with a total of 16 parts being assumed, with 15 parts being PDMS and 1 part being the curing agent 3.5 mL )16=0.2187 mL 0.2187 mL∙15=3.2812 mL PDMS, 0.2187 mL curing agent. For the 10:1, the calculations were done similarly where ten parts were assumed to be the PDMS and 1 part was assumed to be the curing agent for a total of 11 parts resulting in the final equation being 3.5 mL 11=0.318 mL, 0.318∙10=3.181 mL PDMS, 0.318 mL curing.

Fig. 5. The results of the casting with the 15:1 and 10:1. The initial models were cured for roughly 48 hours. Even after the 48 hours recommend curing time the PDMS molds were still incredibly unstable.

After the initial casts of the 15:1 and 10:1 mold, it was realized that the ratios of PDMS in the mixture resulted in very unstable and structurally weak molds (Fig.5). At this point in the experimental process the molds were still curing in standard room temperature, anywhere from 20-23 degrees Celsius. After it was determined that the current ratios of PDMS-to-curing agent ratios that were currently being used resulted in inadequate and unstable molds, the conclusion was made that the next sample of molds would be done in accordance with the following ratios, 11:1, 11:2, 10:1, and 10:2. Between recasting new PDMS molds the B9 printer was in need of a recalibration. Since the project was in the later stages of physical development, the decision was made that the B9 printer should be recalibrated to the desired resolution of 50 μm. The 11:1, 11:2, 10:1, and 10:2 molds were removed and examined. When the molds were released from the casts the 10:2 PDMS casts were noticeably softer and more malleable than the 11:2 casts (Fig. 6B). There also appeared to be signs of PDMS residue left behind upon removing the PDMS casting mold (Fig. 6A, D).

Fig 6 (A.B.C.D: top to bottom, clockwise): The results of the different PDMS curing ratios after the PDMS had been removed.

Upon the realization that the PDMS was stuck to the foundation of its mold during removal, the team made the decision to use mold release and a control group of no mold release on the casts themselves. The team made the decision that based on our previous casts we would utilize the 11:2 ratio PDMS mixture-it was the most structurally sound. On February 11th, 2023, the PDMS a new set of molds were produced 3 casts were done using mold release and 3 were done using the coconut oil. Due to the fact the oven could not be used to increase the curing time these samples were left to cure for 120 hours. Even after the 5-day curing time the molds did appear to be structurally weak (Fig.5). The way in which we have approached the current methods in casting and producing this device align with the current goals of keeping this device reusable and inexpensive.

Fig. 7. Isometric view of V6 Device

Fig. 8. Isometric View of version 11 of the device.

We have been able to create numerous models using the PDMS with little cost. We have also incorporated the technique of washing the PDMS casting trays using the chemical compound known as hexane(s) C6H14. Since hexane was utilized as a washing method-to dissolve the PDMS from the trays has allowed for the reuse of many of the casting trays and keep the costs of printing down. The cost of materials and financial use has been kept to a minimum during the project to a minimum by using low amounts of the PDMS cast silicon base and the caring agent. Based on the calculations previously mentioned, we do not use more than four grams at a time of the PDMS casting and curing agent combined. With a total of six trays for potential casts, there are no more than 24 grams used out of the 200-gram base and 20-gram curing combined.

Device Design Updates

Our previous casts we would utilize the 11:2 ratio PDMS mixture-it was the most structurally sound. On February 11th, 2023, the PDMS a new set of molds were produced 3 casts were done using mold release and 3 were done using the coconut oil. Due to the fact the oven could not be used to increase the curing time these samples were left to cure for 120 hours. Even after the 5-day curing time the molds did appear to be structurally weak (Fig.5). The way in which we have approached the current methods in casting and producing this device align with the current goals of keeping this device reusable and inexpensive.

Fig. 9. Top view of version 12 of the device

We have been able to create numerous models using the PDMS with little cost. We have also incorporated the technique of washing the PDMS casting trays using the chemical compound known as hexane(s) C6H14. Since hexane was utilized as a washing method-to dissolve the PDMS from the trays has allowed for the reuse of many of the casting trays and keep the costs of printing down. The cost of materials and financial use has been kept to a minimum during the project to a minimum by using low amounts of the PDMS cast silicon base and the caring agent. Based on the calculations previously mentioned, we do not use more than four grams at a time of the PDMS casting and curing agent combined. With a total of six trays for potential casts, there are no more than 24 grams used out of the 200-gram base and 20-gram curing combined.

Fig 10. PDMS castings conducted on 2/16/23 where no mold release was utilized.

This section provides a detailed analysis of the advancements in device design and highlights the potential benefits and drawbacks of each advancement. Starting with Version 6 (Fig.7) the device channels and the fluid manifold were the main development. Looking at Figure 7 you can see through the translucent top piece the 3 channels sized to focus 30, 50, and 75nm exosomes. The research focus has shifted towards exploring different ratios of PDMS, in conjunction with varying mold releases and ratios. To enable this, a series of molds were developed that allowed for testing of various combinations of base-to-curing ratios, temperature, and time in the oven. To reduce material usage and accommodate size constraints, the mold size was minimized, and the channels were simplified to only 50 nm.

Fig. 11. Another PDMS casting that was done on 2/16/23/ Left side, was with no use of any type of pf mold release. Right side, with the use of mold release

When deciding between a negative mold (or reverse mold), which produces a negative impression of an object or pattern, and a positive mold (or direct mold), which produces a positive impression, we opted for the latter to create the microfluidic device. The process of creating a positive mold involves multiple steps, starting with mixing the base and curing agent in a specific ratio in a separate dish. The material is then poured into the mold, and air bubbles are removed either through vacuum or manually. Lastly, the mold is placed in the oven for a specific amount of time at a specific temperature.
After the mold material has hardened, it is removed from the object or pattern, revealing a positive impression of the original. The casting material fills the positive space of the mold, taking on the shape of the original object or pattern, resulting in a replica or a copy of the original. Positive molds are an efficient and cost-effective solution for creating multiple copies of an object or pattern for a wide range of applications. Versions 11 and 12 (Fig.8,9) continued the trend of incremental improvements in the mold design, while simultaneously reducing the weight of the mold itself, thus decreasing material costs. Design simplifications enabled the team to increase the effective casting area, further optimizing the device. However, during testing with thinner molds, air bubbles were observed forming on the bottom of the cast. This issue was attributed to an uneven heat distribution across the different regions of the mold. To address this problem, the team decided to keep the 5 sides of the casting mold at a uniform thickness moving forward. As previously mentioned, the ideal ratio of PDMS to curing agent was found to be 11:2, followed by a curing time of 4 hours at 50 °C, which produced the best results. Version 13 onwards, the focus shifted towards developing a functional device for testing and data analysis purposes. To achieve this objective, the team procured the GENIE Touch Syringe Pump platform from PI for precise fluid manipulation and received specialized training on the HIROX lab microscope for obtaining high-resolution images of the device during operation. While the device design is being fine-tuned and made watertight, initial observations are being carried out under a standard lab bench microscope.

Results
So far in the experimental process several microfluidic channel prototypes have been synthesized. Due to variables that have not yet been identified it has been difficult to determine what the causes of the differences of the results were. Figure 10 is an example of a cast that was conducted on February 16,2023. This PDMS was casted with no use of any type of casting mold release. Whereas in figure 11, the right-handed cast was done with the use of mold release. Through these two different samples, we concluded that the mold release in combination with the PDMS had this interaction that prevented the PDMS from fully curing. This effect is more noticeable in figure 12. On February 12, 2023, casts were also conducted. However, these results were profoundly different form the casts that were later done on the 16th. After the initial casts using the mold release, another casting was done to confirm the idea that mold release effected the structure of the PDMS (fig.11). We have however been able to determine that through our casting technique we have been able to maintain some level of resolution. Through a microscope the resolution require has been somewhat confirmed (fig.13). Even though the casting techniques have yet been perfected. The concept is there, and we have been able to produce micro channels.

Fig. 12. Two Casts that were conducted with the use of mold release.

Fig. 13. HiRox microscope image of the microfluidic channels.

Endnotes

1 Siegel RL, Miller KD, Jemal A. Cancer statistics, 2019. CA: A Cancer Journal for Clinicians. 2019;69(1):7-34. doi:10.3322/caac.21551

2 Perumal J, Wang Y, Attia ABE, Dinish US, Olivo M. Towards a point-of-care SERS sensor for biomedical and agri-food analysis applications: a review of recent advancements. Nanoscale. 2021;13(2):553-580. doi:10.1039/d0nr06832b
3 Lee C, Carney R, Lam K, Chan JW. SERS analysis of selectively captured exosomes using an integrin-specific peptide ligand. Journal of Raman Spectroscopy. 2017;48(12):1771-1776. doi:10.1002/jrs.5234

4 Team E. Microfluidics: A general overview of microfluidics. Elveflow. Published online February 5, 2021. Accessed September 14, 2022. https://www.elveflow.com/microfluidic-reviews/general-microfluidics/a-general-overview-of-microfluidics/
5 Kim U, Oh B, Ahn J, Lee S, Cho Y. Inertia–Acoustophoresis Hybrid Microfluidic Device for Rapid and Efficient Cell Separation. Sensors. 2022;22(13):4709. doi:10.3390/s22134709
6 Amini H, Lee W, Carlo DD. Inertial microfluidic physics. Lab Chip. 2014;14(15):2739-2761. doi:10.1039/C4LC00128A
7 Gurung S, Perocheau D, Touramanidou L, Baruteau J. The exosome journey: from biogenesis to uptake and intracellular signalling. Cell Commun Signal. 2021;19:47. doi:10.1186/s12964-021-00730-1

8 Pegtel DM, Gould SJ. Exosomes. Annu Rev Biochem. 2019;88:487-514. doi:10.1146/annurev-biochem-013118-111902
9 Lee C, Carney R, Lam K, Chan JW. SERS analysis of selectively captured exosomes using an integrin-specific peptide ligand. Journal of Raman Spectroscopy. 2017;48(12):1771-1776. doi:10.1002/jrs.5234
10 Perumal J, Wang Y, Attia ABE, Dinish US, Olivo M. Towards a point-of-care SERS sensor for biomedical and agri-food analysis applications: a review of recent advancements. Nanoscale. 2021;13(2):553-580. doi:10.1039/d0nr06832b

Recovery of Fine Details for Fast Imaging Knee Pathologies

By Jasina Yu

Portrait of Jasina Yu

Knee diseases or injuries are very common in the United States. For example, more than 14 million Americans suffer from knee osteoarthritis. Magnetic resonance imaging (MRI), as an interdisciplinary field of computer science, mathematics, engineering, and MR physics, provides an accurate noninvasive assessment of knee pathology. The soft tissue structures (such as menisci, ligaments, and cartilage) and bone marrow of the knee can be visualized for diagnosis and prognosis. However, an MRI scan generally needs 45-90 minutes. As a freshman, I am interested in computer science, mathematics, and physics. MRI integrates those fields, and it is a great research topic to achieve my study goals.

The objective of the project is to advance our understanding of MRI by keeping fine details of knee images. Knee pathologies are accurately visualized without sacrificing imaging speed. The fundamental understanding of the feature representation, extraction, and selection in the artificial intelligence (AI)-based reconstruction process will benefit the knee pathology features’ recovery from highly undersampled data. Detailed information lost in the reconstruction process was studied. This project has helped initiate my research activities at UMD and I hope to advance my career as a researcher and innovator in biomedical imaging investigation.

Based on the preliminary research using the fastMRI dataset [1], our AI-based technique (as shown in the 4^th column of the figure above) can recover more details than the other two methods shown in the 2^nd and 3^rd columns of the figure. The reference knee image is shown in the 1^st column of the figure. Our AI method has closer pathological details to the reference knee image because the other two methods have degraded image quality.

Reference

[1]. Knoll F, et. al. fastMRI: a publicly available raw k-space and DICOM dataset of knee images for accelerated MR image reconstruction using machine learning. Radiol Artif Intell. 2020;2(1): e190007.

Cell Viability of Novel Wound Healing Hydrogels

By Abid Neron

Introduction

Over the summer and my fall semester, I was culturing cells. I started off completely clueless but slowly I started learning and gaining a better understanding of the ins and outs of cell culture. I should start off by explaining what cell culture actually is. Basically, it’s growing a certain cell outside of its normal environment, in a lab. Cell culture is used to study these cells’ growth patterns and how to change their rate of growth. There are multiple cell lines/types, such as skin cells, kidney cells, cancer cells, and much more. I was mostly culturing HEK293 cells which are mammalian kidney cells. I also cultured A375 cells as well, these are a skin cancer cell line. I started off doing cell culture by just following a list of steps telling me what to do. I didn’t understand what I was doing, though. After some research and passaging my cells multiple times, I started to get an understanding of what cell culture is and the steps started making sense. Finally, after perfecting my technique, I wanted to start research using them. I talked to Dr. Tracie Ferreira, and she tasked me with creating a protocol to test cell growth on certain substances. This protocol would be used by the seniors on their final projects. I was introduced to the seniors and their projects and collaborated with them using my knowledge of cell culture.

Abid Neron passaging his cells inside a biosafety cabinet

Methods

Creating a standard protocol to test cell growth (Also known as cell viability) took a lot of research and multiple failed experiments but with each failed experiment I went back to the drawing board and tweaked some steps until I finally found the best method to test cell viability.

My cell viability test uses a substance called Resazurin which is a special dye that changes color depending on cell activity. Cells produce ATP. Resazurin changes color based on the amount of ATP produced. As cell number increases, so does the production of ATP. Further, Resazurin doesn’t affect cells’ growth and doesn’t damage them unlike other cell viability tests. Using a Spectrometer, I can analyze the change in color for each test. The larger the value the more cells were growing. After testing my protocol on students’ substances called Hydrogels, the test offered good results and could be replicated multiple times to get more accurate results if needed. Seniors are currently using the protocol I created to test cell viability on their Hydrogels.

I had an issue with bacteria growing on the hydrogels which would mess up the test, so after multiple experiments, I found the best way to sterilize the hydrogels and keep bacteria away from the cells by using different plates everyday to get more accurate results.

Cell Viability Test

(Notice how the bottom right well is a brighter color, that means that the cells are growing faster!)

Results

I tested my protocol on multiple hydrogels and compared their growth with cells growing under optimal conditions:

A hydrogel’s cell viability over 5 days

Discussion

My research is still ongoing and I’m constantly furthering my knowledge of cell culture and perfecting my technique. Cell culturing has become an almost therapeutic process for me. While there’s a lot to learn, it’s always nice to apply what I’m learning about. Researching cell culture is an incredible experience that I truly loved and sharing my experience with other students and teaching them cell culture and seeing their awe when they see cells growing is always rewarding. I wouldn’t have had this experience if it weren’t for Dr. Trace Ferreira. She taught me everything I know about cell culture and is always there to bounce ideas with. Going forward, I will test more hydrogels and hopefully teach more students how to apply my cell viability test in their own research.

Characterizing the Friction Induced Triboelectric Effect of Polymers

By Viktoriya Balabanova

Portrait of Viktoriya at work in the lab

Introduction

Triboelectric generators (TEGs) use the triboelectric effect between two layers of materials to convert mechanical movement (e.g. sliding) into electric power (Figure 1)^1–4. These generators were developed in recent years and provide the most effective approach to harvest low-frequency mechanical energy for distributed energy applications. Up to now, almost all reported TEGs are designed to work in a charge-saturation state, meaning that more than enough force is used to guarantee maximum triboelectrification of materials in the device, which results in the waste of mechanical energy and low energy conversion efficiency.

Unlike previous studies, our research group hypothesizes that the TEGs will achieve maximum efficiency if they work under the minimum friction force that induces the saturation of triboelectric charges. This hypothesis cannot be tested until we know the friction force-triboelectric charge correlations in materials. This study aims to characterize such correlations in selected polymers. These polymers are the key materials that make the TEGs versatile, efficient, and cost-effective. The results of this project are significant because they will (1) provide preliminary data to test our significant hypothesis about TEGs, (2) help us gain new insights into previously unknown charge transfer mechanisms between two sliding surfaces.

Methods

We designed and built the setup shown in Figure 2, in order to measure the dynamic friction force and triboelectric charge induction simultaneously in a working sliding-mode triboelectric generator (SM-TEG). The whole setup consists of three major parts. Part 1 is a typical SM-TEG, consisted of two acrylic plates, on which adhesive spray is used to first attach stainless steel electrodes and then bind polymer sheets on top of them. Nylon film was used for the top plate  (1×1 inch), and Polytetrafluoroethylene film (PTFE, 1×3 inch ) for the bottom. Part 2 of the setup consists of ATI-Nano17/IP68 six-axis force sensor firmly mounted and suspended from a frame. The top plate of the SM-TEG is attached to a specifically designed and 3-D printed holder, which is connected to the bottom of the force sensor. This second part of the setup remains fixed throughout the whole time data is being collected. In Part 3, a control mechanism is assembled for fine tuning of the normal force and the mechanical energy we put in the system. A very sensitive Newport M-270 Lab Jack is used to adjust the distance between the TEG’s plates, thus increasing or reducing it, allows us to control the normal force applied. For this part we hypothesize that the critical friction force that makes the system saturate can be very susceptible to changes, thus the precision adjustment of the normal force is required. On top of the lab jack a shaker plate PI C-891 is mounted and used to control the sliding mode of the TEG’s bottom plate, including amplitude, frequency and velocity. Another special holder for that plate was designed, 3-D printed and attached on top of the shaker. Lastly, the TEG’s electrodes are connected (open circuit) to a Keithley 6514 electrometer to read out the voltage/current induced by the triboelectric charges.

Results

After the setup was built and calibrated, we initialized some preliminary tests to determine if the data from the force sensor and the electrometer was consistent with the behavior we expected to see. In this process we had to make micro adjustments of the setup, since we needed all parts of the TEG to be aligned and leveled. It was determined that we were ready to begin collecting data and we took several cycles of data sets for various initial forces. The obtained data was further analyzed and produced the results shown in Table 1, then it was plotted to create Figures 3 and 4.

Discussion

This summer research project aimed to characterize the correlation between friction force and triboelectric charge for selected polymers in pre-saturation states. The final results we obtained confirmed the behavior we expected to see. In Figure 3 the averages of the friction force and the applied normal force were analyzed and from the plot we can observe that the friction coefficient between the two polymers used in the TEG has a linear behavior. In Figure 4, the root-mean-squared voltage vs the normal force were examined. The charge was expected to increase with the applied force, until it reaches a saturation point under a critical force. This figure shows that after a certain threshold point, the increase of the normal force applied in the system does not increase the induced voltage. In other words, the TEG has reached a saturated state and even if we put more mechanical energy into it, it does not improve the overall performance of the TEG, resulting in low energy conversion efficiency.

This preliminary data is very important for us since it sets a clear direction for our future work. In the next year we are going to repeat the experiment and try to understand why this behavior happens, how the charge increases with force and how the critical force is affected by material properties. We are hoping to be able to create a model that will help improving the overall efficiency of TEGs, since they are a cost effective, easily manufactured, alternative source of green energy. I would like to thank Ross Jacques for his help on my project, and Dr. Caiwei Shen for his guidance and support, throughout the whole process, without whom this would not be possible!

References:

1. Wang, Z. L. Triboelectric nanogenerators as new energy technology and self-powered sensors – Principles, problems and perspectives. Faraday Discuss. 176, 447–458 (2014). DOI:10.1039/C4FD00159A
2. Xu, G., Li, X., Xia, X., Fu, J., Ding, W. & Zi, Y. On the force and energy conversion in triboelectric nanogenerators. Nano Energy 59, 154–161 (2019). DOI:10.1016/j.nanoen.2019.02.035
3. Zhang, J., Darwish, N., Coote, M. L. & Ciampi, S. Static Electrification of Plastics under Friction: The Position of Engineering-Grade Polyethylene Terephthalate in the Triboelectric Series. Adv. Eng. Mater. 22, 1–5 (2020). DOI:10.1002/adem.201901201
4. Rodrigues, C., Nunes, D., Clemente, D., Mathias, N., Correia, J. M., Rosa-Santos, P., Taveira-Pinto, F., Morais, T., Pereira, A. & Ventura, J. Emerging triboelectric nanogenerators for ocean wave energy harvesting: State of the art and future perspectives. Energy Environ. Sci. 13, 2657–2683 (2020). DOI:10.1039/d0ee01258k
5. Zou, H., Guo, L., Xue, H., Zhang, Y., Shen, X., Liu, X., Wang, P., He, X., Dai, G., Jiang, P., Zheng, H., Zhang, B., Xu, C. & Wang, Z. L. Quantifying and understanding the triboelectric series of inorganic non-metallic materials. Nat. Commun. 11, 1–7 (2020). DOI:10.1038/s41467-020-15926-1

Development of a Thermoplastic Polymer Electrolyte-based Structural Supercapacitor

By Payton Parker

Portrait of Payton Parker 

Introduction

Through the continually evolving world of energy usage, new ways to store energy are becoming increasingly important. For instance, in space technology, finding new ways to store energy in lighter and smaller packages is highly desirable. If weight can be reduced and the amount of stored power can be increased, the space mission durations can be lengthened significantly. To do so, devices called structural supercapacitors were built^1–4. These devices can store electrical energy while being able to support a load. These two properties allow components which originally would be used solely for structural support to also have energy storage capabilities (Figure 1 ⁵). Previous attempts at creating structural supercapacitors use an electrolyte matrix imbedded with carbon fibers functioning as both reinforcement and electrodes. The electrolyte matrix consisted of a resin mixed with ionic liquid. This mixture creates what is called a bi-continuous electrolyte. This complete separation in the electrolyte substantially limits the electrochemical and mechanical performance of the supercapacitor device^6–8.

Dr. Caiwei Shen‘s research group has recently developed a new polymer electrolyte to use in the structural supercapacitor that has much better electrical performance and mechanical properties⁹.  The key feature of this electrolyte is that it is a thermoplastic polymer-based single-phase electrolyte made using melt processing which has never been done before. This melt processing allows for increased ion transport and higher strength of the electrolyte matrix and potentially better performance of the structural supercapacitor devices.

In this project, we are proposing using this same polymer electrolyte in conjunction with carbon fiber fabric to construct new structural supercapacitor devices. The goal is to further improve the electrical and mechanical performance of the supercapacitor. To do this, we will (1) develop a new method for the manufacturing of the devices, and (2) optimize the composition of the electrolyte matrix.

Methods

• • Injection Molding Operation

An A&B Plastics AB-100 injection molder was used for all injection molded samples. This machine uses a pneumatic ram to force the melted material into the mold and must be connected to a compressor. To complete a “shot” (filling the cavity of the mold with molten plastic), the desired temperature of the chamber was set using the PID interface and the pneumatic ram pressure was adjusted using the built-in pressure regulator. At this point, a preheated mold was aligned under injector nozzle. Once the chamber temperature reached its target value, the ram was actuated using a lever filling the mold. After injection, the mold was removed and set aside for cooling. The part was then removed from the mold after a set amount of time.

• DSC Sample Preparation

Sample preparation for differential scanning calorimetry (DSC) was done in an M-Braun Uni-Lab Pro SP glove box. These samples were around 10 mg each and were tested using a TA Instruments DSC machine.

Results

• • Optimized Injection Molding Procedure

The goal in optimizing the injection molding procedure was to find the smallest sample thickness achievable. This is important due to relation between electrolyte thickness and capacitance. The thinner the sample, the thinner the final thickness of the full device, which in turn improves capacitive behavior. The mold shown in figure 1 was designed and machined for this purpose. It features an adjustable insert that can be shimmed to change the depth of the mold cavity from 0.040” to 0.000”. The mold can also be disassembled quickly for cleaning in-between material compositions. 6061 aluminum was chosen as the primary material due to its high thermal conductivity and machinability, however the insert portion was machined from stainless steel. This was done to reduce the chance of the insert becoming seized in place.

Insert mold design

Using this adjustable mold, a set of experiments was designed to determine the best injection parameters for polyethylene terephthalate (PET). PET was chosen for these tests as it was the preferred material used for the matrix portion of the polymer electrolyte. Using the typical design of experiments layout made for multifunctional optimization, an initial set of parameters were established and used a basis for testing. Four separate tests were then done, varying each parameter one at a time. The characteristics of each result were carefully noted on for analysis at the end of each test set. In the following tables, each row highlighted in green represents the best result for the given experimental set. Characteristics such as clarity and ease of molding were the main forms evaluation.

From this procedure, it was determined that the best parameters for PET were the following: mold temperature of 160°C, barrel temperature of 270°C, injection pressure of 60 psi, and a minimum cavity depth of 0.020”. These parameters resulted in the most consistent, clear samples.

• DSC Results

Differential scanning calorimetry was used to characterize two different polymer electrolyte materials. The first of which was PET+20%LiTSFI shown in figure 2. From the figure, it can be seen that the melting point is located around 234°C. The second was PLA+20%LiTSFI shown in the following figure.

Discussion

Throughout this research project, many impactful discoveries were made. Most importantly a basis for injecting solid polymer electrolyte samples was established. Now the only step needed for injecting different compositions of electrolytes (changing the total lithium salt to polymer matrix ratio) was a DSC test to find the melting point of the specific composition. The other parameters could then be adjusted based on this temperature. On top of this, the DSC tests revealed that the PLA based electrolyte has a more definite glass transition point, around 50°C. This means even in a mostly solid phase, the PLA+20%LiTSFI begins to flow at low temperatures. This characteristic may be instrumental when attempting to impregnate weaved carbon fibers in future work.

It was lastly discovered that humidity plays a major role in the injection molding process. The ambient environment where the injection molding was done tended to have high humidity levels between 50-70%. It is well known that water content can significantly impact injection molding, so every precaution was taken including drying the material before injection, sealing the injection molding barrel when not in use, and preheating the barrel before injection. Unfortunately, these attempts only had a small impact on the results. Many of the samples were still dark in color due to water that was absorbed by the injection material. For this reason, a senior design team was sponsored in the mechanical engineering department to solve this humidity control issue.

References

1. Xu, Y., Lu, W., Xu, G. & Chou, T. W. Structural supercapacitor composites: A review. Compos. Sci. Technol. 204, 108636 (2021). DOI:10.1016/j.compscitech.2020.108636
2. Snyder, J. F., Gienger, E. B. & Wetzel, E. D. Performance metrics for structural composites with electrochemical multifunctionality. J. Compos. Mater. 49, 1835–1848 (2015). DOI:10.1177/0021998314568167
3. Reece, R., Lekakou, C. & Smith, P. A. A structural supercapacitor based on activated carbon fabric and a solid electrolyte. Mater. Sci. Technol. (United Kingdom) 35, 368–375 (2019). DOI:10.1080/02670836.2018.1560536
4. Shirshova, N., Qian, H., Houllé, M., Steinke, J. H. G. G., Kucernak, A. R. J. J., Fontana, Q. P. V. V, Greenhalgh, E. S., Bismarck, A. & Shaffer, M. S. P. P. Multifunctional structural energy storage composite supercapacitors. Faraday Discuss. 172, 81–103 (2014). DOI:10.1039/c4fd00055b
5. Structural supercapacitor illustration. https://scitechdaily.com/big-breakthrough-for-massless-energy-storage-structural-battery-that-performs-10x-better-than-all-previous-versions/
6. Shirshova, N., Bismarck, A., Carreyette, S., Fontana, Q. P. V., Greenhalgh, E. S., Jacobsson, P., Johansson, P., Marczewski, M. J., Kalinka, G., Kucernak, A. R. J., Scheers, J., Shaffer, M. S. P., Steinke, J. H. G. & Wienrich, M. Structural supercapacitor electrolytes based on bicontinuous ionic liquid-epoxy resin systems. J. Mater. Chem. A 1, 15300–15309 (2013). DOI:10.1039/c3ta13163g
7. Tu, V., Asp, L. E., Shirshova, N., Larsson, F., Runesson, K. & Jänicke, R. Performance of bicontinuous structural electrolytes. Multifunct. Mater. 3, 025001 (2020). DOI:10.1088/2399-7532/ab8d9b
8. Greenhalgh, E. S., Ankersen, J., Asp, L. E., Bismarck, A., Fontana, Q., Houlle, M., Kalinka, G., Kucernak, A., Mistry, M., Nguyen, S., Qian, H., Shaffer, M., Shirshova, N., Steinke, J. & Wienrich, M. Mechanical, electrical and microstructural characterisation of multifunctional structural power composites. J. Compos. Mater. 49, 1823–1834 (2015). DOI:10.1177/0021998314554125
9. Joyal, N., Chang, Y.-C., Shonar, M., Chalivendra, V. & Shen, C. Solid polymer electrolytes with hydrates for structural supercapacitors. J. Energy Storage Accepted (2022).
10. Anjum, N., Grota, M., Li, D. & Shen, C. Laminate composite-based highly durable and flexible supercapacitors for wearable energy storage. J. Energy Storage 29, 101460 (2020). DOI:10.1016/j.est.2020.101460