Characterization and Testing of the Passive Magnetic Attitude Control System for the 3U AstroBio CubeSat

AstroBio CubeSat is a mission funded by the Italian Space Agency aimed at validating novel lab-on-chip technology, that would enable the use of micro- and nanosatellites as autonomous orbiting laboratories for research in astrobiology. This 3U CubeSat is equipped with a passive magnetic attitude control system (PMACS), including permanent magnets and hysteresis strips, which allows for stabilizing the spacecraft with the longitudinal axis in the direction of the geomagnetic field vector. This work presents the process followed for the experimental characterization of the system, performed on the engineering unit of the satellite by using a Helmholtz cage facility and a spherical air-bearing to recreate environmental conditions similar to the ones experienced during the orbital motion. The hysteresis strips are characterized starting from the determination of the hysteresis loop, from which the energy dissipation per cycle and the apparent magnetic permeability are extracted. Tests performed by using the Helmholtz cage and the air-bearing facility allows for further investigating the damping torque produced by the PMACS and validating the abovementioned parameters. Numerical analysis is then used to select the number of permanent magnets which allows for achieving a pointing accuracy within an error of 10° within 24 h from the deployment. The analysis of the flight data supports the results obtained from the experimental test campaigns, confirming the effectiveness of the proposed methods and of the PMACS design

On-chip cell-culture support and monitoring device with integrated thin-film sensors and actuators

This work describes the design, fabrication and test of a lab-on-chip device along with its front-end electronics for the execution of experiments on bacterial cultures on nanosatellite missions. The motivations for such systems lie in the need to improve the quantification of the effects of the space environment on living organisms and facilitate the development of countermeasures to mitigate them. Ground-based studies often suffer the limitations of the available risk models for radiation exposures beyond low-Earth orbit arising from the difficulty to fully reproduce the deep-space energy spectrum and the multi-directional flux of the cosmic radiation. On the other hand, in-situ experiments have been mainly limited by the need of human support for their execution thus restricting them to space station missions or sample-return missions and, up to now, only few biology-oriented cubesat missions have been launched or scheduled for the near future. In this framework, the proposed payload aims to enable extended in-situ studies taking advantage of the characteristics of nanosatellite missions as low-cost and timing. The constraints of nanosatellite missions guided the definition of the system requirements, with particular focus on device compactness, power consumption and data budget that proved to represent the main limitations toward the implementation of biological experiments in small (up to 3U) cubesats. The proposed payload is based on an on-chip micro-incubator with integrated thin-film sensors and actuators for the active control of the environmental conditions of a bacterial culture and for the monitoring of its metabolic status. The device is composed of an incubation chamber connected to a microfluidic network designed to ensure the supply of nutrients and/or pharmaceuticals in a controlled manner in order to enable different experimental protocols, according to the type of cells and experiment target. The micro network is bonded on a glass substrate on which hydrogenated amorphous silicon sensors and thin-film resistive heaters are fabricated. The on-chip photodiodes allow the implementation of luminescence-based analytical protocols commonly used in laboratory. Accurate temperature control is achieved by means of additional on-chip thin film diodes and a transparent indium-tin-oxide heater located beneath the culture chamber

Micro-incubator based on lab-on-glass technology for nanosatellite missions

The study and quantification of the effects of the space environment on human body is a primary task for future manned deep space missions. The risk models for radiation exposures incurred by astronauts beyond low-Earth orbit, have different limitations due to the difficulty to have terrestrial parallels on which to base risk estimates. Indeed, no terrestrial sources fully reproduce the deep space energy spectrum and the multi directional flux of the cosmic radiation. In situ analysis would therefore be fundamental in order to enable reliable studies about the effects of the radiation environment on living organisms as well as to evaluate customized radiological countermeasures for astronauts. A micro-incubator suitable for cubesat missions for studying in situ the effects of the space environment on cellular cultures is presented. The device is based on lab-on-chip technology with integrated thin-film sensors and actuators for the active control of the environmental conditions of the cell culture and for the monitoring of its metabolic status. In particular, the device includes an incubation chamber connected to a microfluidic network for the supply of nutrients and/or pharmaceuticals. A second network is used for the distribution of carbon dioxide through a thin gas-permeable membrane. On-chip on-demand production of carbon dioxide can be eventually achieved from the pyrolysis of sodium bicarbonate stored in a separate reservoir with a dedicated thin film heater. The same network can be used to supply a controlled atmosphere from a pressurized tank. The on-chip hydrogenated amorphous silicon photodiodes are used to measure the light emitted by genetically-modified cell cultures that express a bio-luminescent behavior when subjected to given stress conditions. Accurate temperature control is achieved by means of additional on-chip thin-film diodes and a transparent indium-tin-oxide heater located beneath the incubation chamber. From technological point of view, the system relies on the combination of different thin- and thick-film fabrication technologies jointly used with the aim to achieve a compact, automated and low-power device that represents a viable solution for biological experiments aboard cubesat satellites

Characterization of temperature distribution in microfluidic chip for DNA amplification

This work focuses on the temperature monitoring inside a polydimethylsiloxane microfluidic chip, suitable for DNA amplification. In order to achieve this aim, the microfluidic chip has been thermally coupled with a labonchip integrating, on a single glass substrate, temperature sensors and thin film heater. The wells of the chip have been filled with thermochromic liquid crystals, that change their optical properties at a precise transition temperature (TT). Experiments have been performed cycling the chip temperatures between 90 °C and 50 °C, two temperatures very close to the annealing and denaturation steps of the standard Polymerase Chain Reaction (PCR), utilized for DNA amplification. Results state that the temperature distribution inside the wells follows values and spatial uniformity required by the PCR cycles, guaranteeing an effective heat transfer from the thin film resistor to the microfluidic chip. Gel electrophoresis of amplified samples showed the presence of the amplifications and thus the successful implementation of the PCR in our lab-on-chip

Integrated 3D Microfluidic Device for Impedance Spectroscopy in Lab-on-Chip Systems

In this paper we demonstrate the implementation of a micro-scaled integrated system with the aim to sort, estimate and monitor the biomass of living cancer cells suspended in a culture medium. For this purpose, a 3D microfluidic network is designed to route small volumes of biological samples to the testing sites and dielectric spectroscopy is chosen as investigation method. Comparative electrical analyses are guaranteed by the separation of sole medium and medium-cells mixture in two different areas of the chip. A polyimide-based micro-sieve, placed between two microfluidic channels, is used to perform cell filtering and sorting. Two couples of thin-film metal electrodes ensure the comparative dielectric measurements of the separated materials. Preliminary experiments were carried out in order to test the microfluidics and demonstrate its particle-separating capabilities. The first results prove the robustness of the chosen materials, the effectiveness of the micro-sieving device in terms of particle separation from a liquid solution and its successful integration in the microfluidics. The proposed system represents a promising step for the development of novel valid solutions in the field of micro-scaled integrated cell sorting, cell monitoring and cell counting for a wide range of applications, such as tissue engineering, tumor cells research and biological monitoring in space environmen

Flexible microfluidic networks enabling rapid prototyping of novel surface chemistries in lab-on-chip

In this work, a flexible microfluidic network based on double-sided pressure sensitive adhesive (PSA) tape, a functionalized sensing glass substrate and an array of amorphous silicon photosensors (a:Si-H) are combined to achieve a lab-on-chip (LoC) system for biosensing applications. The system features rapid and low cost development of prototypes for testing novel surface chemistry and shows analytical performances comparable to those of state-of-the art for LoC devices

Split aptamers immobilized on polymer brushes integrated in a lab-on-chip system based on an array of amorphous silicon photosensors. A novel sensor assay

Innovative materials for the integration of aptamers in Lab-on-Chip systems are important for the development of miniaturized portable devices in the field of health-care and diagnostics. Herein we highlight a general method to tailor an aptamer sequence in two subunits that are randomly immobilized into a layer of polymer brushes grown on the internal surface of microfluidic channels, optically aligned with an array of amorphous silicon photosensors for the detection of fluorescence. Our approach relies on the use of split aptamer sequences maintaining their binding affinity to the target molecule. After binding the target molecule, the fragments, separately immobilized to the brush layer, form an assembled structure that in presence of a “light switching” complex [Ru(phen)2(dppz)]2+, emit a fluorescent signal detected by the photosensors positioned underneath. The fluorescent intensity is proportional to the concentration of the target molecule. As proof of principle, we selected fragments derived from an aptamer sequence with binding affinity towards ATP. Using this assay, a limit of detection down to 0.9 µM ATP has been achieved. The sensitivity is compared with an assay where the original aptamer sequence is used. The possibility to re-use both the aptamer assays for several times is demonstrated

Lab-on-chip for integrated cell culture monitoring

Conductance spectroscopy, performed by measuring the electrical complex conductivity of the sample, can be a valid analytical method for cell cultures monitoring. The electromagnetic properties of inhomogeneous materials, and in particular of biological materials, are expressed in terms of complex conductivity, or permittivity, and are strictly related to shape, dimensions, volume fraction occupied by the particulate (cells) [1]. This technique allows, in a simple and non-invasive way, the real time determination of the cell volume fraction and the average size of the cells in the volume under measurement. Over the last years, Lab-on-Chip systems have increased their popularity in the field of biomolecular analysis due to their key features, such as reduced dimensions, capability to integrate and perform each step of the biomedical analysis in a single chip, quick response time, low reagents’ consumption and on-field use together with the opportunity to avoid bulk equipment and copious specialized personnel. All these advantages were made possible by the evolution of microelectronic technologies and their capability to adapt to different substrates and materials. This work presents the development of an integrated Lab-on-Chip system (see Fig. 1) with the aim to sort and estimate the biomass of living cancer cells suspended in culture medium via dielectric spectroscopy. The separation of sole medium and medium-cells mixture in two different areas of the chip is guaranteed by a polyimide-based membrane (see Fig. 2) [2] capable of performing cell filtering and placed between two microfluidic channels. Two couples of thin-film metal electrodes ensure a comparative dielectric investigation of the separated materials. Preliminary experiments have been performed in a bulk solution at three different cell concentrations. Results reported in Fig. 3 show a clear trend in the measured conductance and susceptance of the solution as a function of frequency. Further experiment will be performed in the lab-on-chip with and without the selective membrane and the achieved result will be compared to the theoretical model [1]. The proposed lab-on-chip represents a promising step for the development of novel valid solutions in the field of integrated cell sorting, cell monitoring and cell counting for a wide range of applications, from tissue engineering to biological analysis in space environment

RNA/DNA amplification methods for the detection of bacteria and virus through an optoelectronic lab-on-chip

This paper focuses on the detection of bacteria and virus achieved by means of a miniaturize portable lab-on-chip (LoC) able to perform RNA/DNA amplification. The LoC is constituted by homemade microfluidic chips which are optically and thermally coupled to an optoelectronic (OP) thin film platform. OP device combines on a single glass substrate thin film heater, sensors for temperature control, and photosensors for fluorescence detection. The LoC was tested for performing loop mediated isothermal amplification (LAMP) for the detection of the bacteria Xylella fastidiosa subsp. pauca (Xfp) and real-time reverse transcription polymerase chain reaction (RT-qPCR) of watermelon mosaic virus, respectively

PLEIADES: A highly integrated lab-on-chip system for the detection of life markers in extraterrestrial environments

The detection of biomarkers of past or present life is a high priority task for the astrobiological exploration of the Solar System, currently pursued through in situ analyses by gas chromatography coupled with mass spectrometry. Lab-on-chip systems are under study as a very promising alternative approach, offering high specificity and detectability and minimizing employed resources as volume, mass, power consumption. In this work, we present PLEIADES: Planetary Life Explorer with Integrated Analytical Detection and Embedded Sensors, which is a chemiluminescence-based, highly integrated analytical platform for the detection of life biomarkers outside of the Earth. The main challenge for any search-for-life mission consists in determining whether an observation can be uniquely attributed to a biological signature. For this reason, it was devised a scoring system for assigning a confidence value to a group of observations. Basing on the hypothesis that life developed on extraterrestrial environments would follow similar evolutionary principles as in Earth, the adenosine 5-triphosphate (ATP) molecule scored as a high priority extant life biomarker and was selected as target molecule to test the developed system. The PLEIADES lab-on-chip goes beyond the current approaches that still require bulky external instrumentation for their operation. It exploits a capillary force-driven microfluidic network, thus avoiding external pumps for sample and reagents handling, an array of thin-film hydrogenated amorphous silicon (a-Si:H) photosensors for photons detection, and chemiluminescence bioassays to provide highly sensitive analyte detection in a very simple and compact instrumental configuration (no need for lamps and filters). The microfluidic chip is functionalized with receptors such as antibodies and aptamers, using polymer brushes. The sample is owed into the microfluidic network and upon the interaction between the life markers and the receptors, a chemiluminescence signal is generated and detected by the photosensors positioned underneath. Besides the compact size and the minimal weight, the PLEIADES chip has additional positive features for space applications. The monolithic integration of sensors and detection site on the same glass substrate leads to intrinsic mechanical stability without the risk of misalignment between sensors and reaction sites due to e.g. vibrations or shocks. The absence of pumping devices as well as radiation sources significantly reduces the overall power consumption. Finally, the use of self-aligned photosensors for each immunoreaction site reduces the amount of generated data without reducing the quantity and quality of the analytical information providing a faster data processing and reduced storage and transmission bandwidth requirements