Polymer-based and Functionalized 3D Microelectrode Array (MEA) Biosensors

Microphysiological systems are three-dimensional (3D) in vitro systems that recapitulate crucial biological aspects of cell heterogeneity and native tissue architecture by mimicking complex structures that are impossible in two-dimensional (2D) cell cultures. Microelectrode arrays (MEAs) are biosensors used to spatially and temporally monitor the activity of microphysiological systems by transducing cellular signals into electronic signals to provide quantitative data on the in vitro system. Conventional MEAs are typically planar in nature, however, 3D MEAs offer several advantages such as better simulation of an in vivo cellular environment and improved signal-to-noise ratio and cell-electrode coupling. MEA fabrication utilizing traditional cleanroom methods is rather extensive, expensive, and specialized, therefore this thesis presents a transition from 2D MEAs fabricated via the cleanroom approach to 3D MEAs fabricated via the makerspace approach utilizing polymers. The first study in the thesis discussed the fabrication and characterization of 2D MEA devices using cleanroom methods and investigated post-processing methods to address limitations that arise for planar devices. The next study introduced the makerspace approach, where benchtop techniques were used to successfully fabricate and characterize a fully functional 3D MEA. A subsequent study investigated another benchtop method to define an electrical insulation using a pour-spin method of polystyrene solution. However, there was a challenge of adhesion of the PS to the substrate, which was improved by both utilizing another type of printer and functionalizing these surfaces with polydopamine. In the final study of the thesis, a benchtop technique called electrospinning was used to define synthetic polymer-based nanofibers atop of the 3D MEAs to simulate extracellular matrices as well as demonstrate their potential as drug delivery systems. This thesis demonstrates the highly versatile nature of makerspace microfabrication utilizing polymers to allow for new processes that offer advanced functionalities when producing microdevices such as 3D MEAs interfacing with microphysiological systems

Controlled drug release from polyelectrolyte–drug conjugate nanoparticles

Hydrophobic drugs are grafted to polyelectrolytes to produce nanoparticles that deliver and release drugs in cells.</p

Fabrication And Characterization Of 3D Printed, 3D Microelectrode Arrays With Spin Coated Insulation And Functional Electrospun 3D Scaffolds For “Disease In A Dish” And “Organ On A Chip” Models

We demonstrate a new fabrication technology for 3D Microelectrode Arrays (MEAs) to stimulate and record electrophysiological activity from cellular networks in-vitro. Electrospun Polyethylene Terephthalate (PET) 3D scaffolds are coupled to the fabricated MEAs which make them fully functional for “disease in a dish” and “organ on a chip” models to promote cell/tissue growth and regeneration. The microfabrication technology involves 3D towers realized by 3D printing and a metallization layer, defined by stencil mask evaporation techniques. Multiple insulation strategies are reported: a drop-casted/spin-coated 3D layer of Polystyrene (PS) and an evaporated layer of SiO2, both of which are laser micromachined to realize the 3D microelectrodes

Microgravity Effect on Bacterial Growth: Further Clarification of the Underlying Mechanism

Wenyan Li, NASA Kennedy Space Center, USAAngie Diaz, NASA Kennedy Space Center, USATesia Irwin, NASA Kennedy Space Center, USANilab Azim, NASA Kennedy Space Center, USAAubrie O'Rourke, NASA Kennedy Space Center, USAICES303: Physico-Chemical Life Support- Water Recovery & Management Systems- Technology and Process DevelopmentThe 53rd International Conference on Environmental Systems was held in Louisville, Kentucky, USA, on 21 July 2024 through 25 July 2024.Gravity interacts with other physical environmental factors to impact the formation of today's Earth and contribute to biological variations between water and land species. Microbes, with their simple structures and small sizes, are expected to be less gravity-sensitive than larger species. However, microgravity can greatly impact the mass transfer and interface behavior in the extracellular environment, and various effects of spaceflight on bacterial growth have been observed. Our earlier literature review summarizes the systematic efforts to understand the spaceflight effect on microbial growth through the extracellular mass transfer mechanism and provides an in-depth literature review to address some discrepancies observed in the literature. This paper analyzes the effects of microgravity on the extracellular environment, and their potential effect on bacterial growth, to further clarify the underlying mechanism of the microgravity effect on bacterial growth

Precision Plating of Electrogenic Cells on Microelectrodes Enhanced with Nano-Porous Platinum for Cell-Based Biosensing Applications

Microelectrode Array (MEA) devices are well established platforms for biosensing applications, however, limitations in electrode materials and cell coupling to electrodes still exist. Signal-to-noise ratio (SNR), a fabrication limitation, can be improved by reducing the impedance of the microelectrodes without increasing their physical size using conductive nanomaterials. Platinum is a well-studied conductive material that has been determined to be compatible with MEA devices, contains high electronic conductivity, is non-toxic to cells and has excellent catalytic activity. Nano-porous platinum, as compared to pure platinum, has larger surface area enabled by nano-scale definition, and as a result can lower the impedance of microelectrodes. Therefore, in this study nano-porous platinum was electroplated onto thin film gold electrodes to increase SNR in a single-well MEA device. Numerous commercial and research grade MEAs are available and have been subject to for various applications such as disease modeling and pharmaceutical screening. Although high densities of cells can increase the probability of cell-electrode coupling, only signals near electrodes will be detected. Our approach introduces a method of precise patterning of cells on electrodes to increase the probability of cell-electrode coupling and reducing inaccuracies and expenses associated with cell plating. The single-well MEA glass die was designed and fabricated to contain 64 microelectrodes (30 µm diameter with a pitch of 200 µm) and 4 internal on-chip reference electrodes. The MEA glass die fabrication was performed on a 4-inch, 500 µm thick glass wafer. First, metal traces composed of titanium and gold were deposited using lift-off lithography. Subsequently, 5 µm of SU-8 was spin coated and defined as an insulation layer. A separate printed circuit board (PCB) was designed and fabricated to contain 72 contact pads and routing traces. The biocompatible epoxy 353ND was used to package the glass die and PCB in specific orientations determined by alignment markers. Ball bonding with 20 µm diameter gold wire was used to wirebond the glass die to the PCB. A packaging technique was developed that would allow the characterization of key properties of the MEA. This technique involved using copper wire, 100 µm in diameter, and attaching it to the contact pads on the backside of PCBs using a conductive epoxy. Finally, a polystyrene culture well and lid were attached to the MEA using the epoxy, 353ND. Nano-Porous platinum electroplating solution was prepared with a combination of chloroplantinic acid, HCl and lead acetate, all diluted in DI water. Fully packaged devices containing approximately 3 mL of electrolyte were placed within the Axion BioSystems Muse for nano-porous platinum electrodeposition, utilizing the custom Application Specific Integrated Circuit (ASIC) in the system at room temperature. The nano-porous platinum electroplated devices were subsequently characterized using electrical impedance spectroscopy and cyclic voltammetry against the control devices, which contained gold electrodes. The impedance of each device was measured across a scanned frequency range of 10 Hz-100 kHz between the microelectrode, the internal reference electrode and cellular conductive media. The impedance of the nano-porous platinum devices is an order of magnitude lower than the devices with gold electrodes. Cyclic voltammograms were obtained at a scan rate of 20 mV/s in the range from -0.28 to 1.2 V vs. Ag/AgCl. RMS noise comparison between nano-porous platinum electroplated devices and control devices (gold electrodes) was determined using the Muse system and Axion’s Integrated Studio (AxIS) software. Biosensing applications for the devices were explored using electrogenic cells in combination with a precise plating technique. As depicted in Figure 1, cells were positioned in a pattern on and around electrodes to increase the probability of cell-electrode coupling. The electrical response was obtained and analyzed using the Muse system and AxIS software. SNR of action potentials recorded from cells growing on devices enhanced with nano-porous platinum electrodeposition and cells on control devices with gold electrodes were compared. Activity within neuronal networks / beat frequencies of cell patches on electrodes were monitored over the course of 2-3 weeks. The methods explored in this study not only decreases impedance of microelectrodes to increase SNR but also increases cell-electrode coupling by warranting the placement of cells next or on the electrodes by precision patterning. Future studies will aim to optimize electrode sensitivity using novel electrode materials, the porosity of different materials, and characterization using emerging analytical methods. Eventually these devices will provide in vitro systems to monitor both acute and chronic effects of drugs and toxins as well as to perform functional studies under physiological or induced pathophysiological conditions that mimic in vivo damages. Figure 1: Electrogenic cells patterned near nano-porous platinum electrode Figure 1 <jats:p /

Multi-Modal Microelectrode Arrays For The Investigation Of Protein Actin’S Electro-Mechanosensing Mechanisms Toward Neurodegenerative Disease Models On A Chip

We have developed multi-modal Microelectrode Arrays (MEAs) with electrodes and microfluidics, with successful manipulation of actin filaments and bundles onto the devices for electro-mechanosensing studies. The application of our MEAs to the characterization of actin filaments/bundles will allow fundamental understanding of actin cytoskeleton’s mechanical and electrodynamic properties in neurodegenerative disease signatures on a chip

Literature Review of Disinfection Techniques For Water Treatment

Nilab Azim, University of Central Florida, USAngie Diaz, Amentum, USWenyan Li, Amentum, USTesia Irwin, The Bionetics Corporation, USLuz Calle, National Aeronautics and Space Administration, USMichael Callahan, National Aeronautics and Space Administration (NASA), USALiterature Review of Disinfection Techniques For Water TreatmentThe proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.Water treatment is a developing concern, both terrestrially and in spacecraft, as exploration missions extend in time and distance. Current biofilm control is limited for long-term applications. To optimize biocides for present and future space exploration vehicles, a thorough understanding of common and traditional disinfectant techniques is required. This review is focused on the three fundamental disinfection techniques: chemical, physical, and biological. Mechanisms, advantages, disadvantages, and specific properties of each major technique, as well as their studied effect on established biofilms, are also considered. This paper provides a general background on disinfectants and some information on effects on biofilms that can be useful to develop innovative ideas for state-of-the-art disinfection techniques for water treatment in specific environments, such as those currently posing mission risks as well as for future spacecraft water system development

Four-Dimensional Printing of Multi-Material Origami and Kirigami-Inspired Hydrogel Self-Folding Structures

Four-dimensional printing refers to a process through which a 3D printed object transforms from one structure into another through the influence of an external energy input. Self-folding structures have been extensively studied to advance 3D printing technology into 4D using stimuli-responsive polymers. Designing and applying self-folding structures requires an understanding of the material properties so that the structural designs can be tailored to the targeted applications. Poly(N-iso-propylacrylamide) (PNIPAM) was used as the thermo-responsive material in this study to 3D print hydrogel samples that can bend or fold with temperature changes. A double-layer printed structure, with PNIPAM as the self-folding layer and polyethylene glycol (PEG) as the supporting layer, provided the mechanical robustness and overall flexibility to accommodate geometric changes. The mechanical properties of the multi-material 3D printing were tested to confirm the contribution of the PEG support to the double-layer system. The desired folding of the structures, as a response to temperature changes, was obtained by adding kirigami-inspired cuts to the design. An excellent shape-shifting capability was obtained by tuning the design. The experimental observations were supported by COMSOL Multiphysics&reg; software simulations, predicting the control over the folding of the double-layer systems

Environmental Testing of a Fully Automated Carbothermal Reactor for Lunar Oxygen Production

Nathan P. Haggerty, Sierra Space Corporation, United StatesBrant C. White, Sierra Space Corporation, United StatesAaron Paz, NASA Johnson Space Center (JSC), United StatesDesmond O'Connor, NASA Johnson Space Center (JSC), United StatesNilab Azim, NASA Kennedy Space Center (KSC), United StatesJanine Captain, NASA Kennedy Space Center (KSC), United StatesICES308: Advanced Technologies for In-Situ Resource UtilizationThe 54th International Conference on Environmental Systems was held in Prague, Czechia, on 13 July 2025 through 17 July 2025.Oxygen comprises the majority of propellant mass required for ascent from the lunar surface and for in-space chemical propulsion. Using in-situ resource utilization (ISRU) technologies to produce oxygen on the moon enables a robust lunar economy through a dramatic reduction in lunar launch costs. In the Summer of 2024 Sierra Space completed thermal vacuum (TVAC) testing of a flight-like Carbothermal Oxygen Production Reactor (COPR) through a NASA Tipping Point program. The COPR reactor uses a mass efficient, scalable architecture optimized for a lunar technology demonstration mission. Concentrated solar energy is directly applied to the lunar regolith simulant. The insulating material properties of the regolith isolate the corrosive molten material from the reactor walls and other hardware. This approach allows for a completely passive thermal control system where high temperature (~1800°C) carbothermal processing is performed without requiring exotic materials or complex cooling systems. The reactor also includes an end-to-end automated solid material handling system capable of metering the lunar regolith simulant from a supply hopper into a pressurized volume, weighing it, distributing it into the carbothermal reactor, and removing the reduced metallic slag. Sierra Space demonstrated repeated use of the automated material handling, gas handling and carbothermal reduction processing systems inside NASA JSC’s “dirty” TVAC chamber while at the relevant lunar topographical, vacuum, and temperature conditions. This testing matured key hardware to TRL 6. Oxygen extraction and performance measurements were taken by the NASA KSC Mass Spectrometer Observing Lunar Operations (MSolo) team using a commercial version of their flight instrument. Oxygen extraction energy efficiency and production yield from regolith exceeded the program goals. The COPR system will be integrated with a flight forward solar concentrator, optical shutter, gas analysis system, avionics, and software as a part of the NASA CaRD program integrated testing in early 2025