The Biofilm Onboard Radiation Exposure Assessment Lab In Space (BOREALIS) mission is a 6U CubeSat initiative funded by the Italian Space Agency under the ALCOR program, executed through a collaboration among the School of Aerospace Engineering of Sapienza University of Rome, Interdepartmental Centre for Industrial Aerospace Research (CIRI Aerospace) of the University of Bologna and Kayser Italia Srl. BOREALIS is equipped with a lab-on-chip payload for studying the effects of microgravity and ionising radiation on microbial biofilms, which are crucial for understanding and preventing persistent infections in space environments. The satellite will operate across multiple orbits, moving from low to medium Earth orbit, to distinctly analyse the impacts of radiation separate from microgravity. The required orbital transfer not only tests the autonomy of its on-board systems in challenging conditions but also places BOREALIS among the first and few CubeSats to have ever attempted such a complex manoeuvre. This study explores the systematic application of Model-Based Systems Engineering to satellite design, from conceptualisation to trade-offs, using a tradespace analysis approach supported by Monte Carlo simulations to optimise mission configurations against performance and cost. Additionally, the adaptability of Model-Based Systems Engineering tools and the reusability of such an approach for other satellite projects are discussed, illustrating the BOREALIS mission as a case study for small mission design considering constraints and requirements.

IntroductionAstroBio CubeSat (ABCS) is an Italian Space Agency (ASI) 3U CubeSat (100x100x340 mm) selected by European Space Agency (ESA) to be launched with the Vega C qualification maiden flight, as piggy back of the ASI LARES2 main satellite, by the end of 2020. ABCS will be deployed in an approximately circular orbit, with about 5900 km altitude and 70° of inclination. It implies that ABCS will spend a significant part of the orbital period within the internal Van Allen belt, close to its maximum. The radiation environment is characterized by a very high flux of charged particles, which have a significant effect on electronic components in terms of permanent damages due to accumulated dose effects and single events. Considering the extremely harsh space conditions, the estimated mission lifetime useful to perform the payload experiments should be defined in 3 months.ABCS Project is funded and managed by ASI in cooperation with INAF-Astrophysical Observatory of Arcetri, that will coordinate the scientific and engineering team. Partners of the projects are the School of Aerospace Engineering of Sapienza University of Rome, the University of Bologna, the University of Torino, and Kayser Italia.ABCS PayloadABCS will host a mini laboratory payload based on an innovative lab-on chip technology suitable for research in astrobiology. The objective is to test in space environments an automatic laboratory able to provide a highly integrated in-situ multiparameter platform that uses immunoassay tests exploiting chemiluminescence detection by means of on-chip a-Si:H photodiodes. The experiment will consist in a set of lateral flow immunoassays (LFIA) on nitrocellulose support where target biomolecules are immobilized in specific test areas. Reagents are deposited in a non-permanent fashion and in a dry form in the initial part (starting area) of the microfluidic path. When the reagents-delivery-system provides a volume of liquid reagent to the starting pad, capillary forces will guide the reagents through the LFIA microfluidic pathway. During the flow, liquid reagents will solubilize and transport along the path the deposited reagents, triggering specific reactions and allowing the chemiluminescence detection by the photodiodes.ABCS also mounts an ancillary radiation dose payload, to investigate the degradation of of electronic components exposed to the space environment. The device has twin components protected by established radiation screens, kindly provided by Thales Alenia Space Italia and by CESI, so that the degradation can be assessed on the basis of the difference between the observed currents.ABCS architecture and payload are based on the strong heritage gained by the research team with the ground validation of the PLEIADES (Planetary Life Explorer with Integrated Analytical Detection and Embedded Sensors) instrument, an R&D ASI project recently concluded.Enviromental challengesThe main challenges of the project are to mitigate the effects of the expected very high flux of charged particles, keeping the correct temperature (4°C/25°C) and pressure (about 1 atm) range for the payload to prevent reagents degradation. This invoked a series of technological solution to protect the payload. The pressurized environment is ensured by an inner aluminium box, hosting both the experiment and the main subsystems (batteries, on-board data handling, telemetry, tracking and control) hermetically sealed and providing shielding from radiation and charged particles. A thermal control system, including a passive control multi-layer insulation and an active heather mounted inside the pressurized box, maintain the temperature in the desired range.ConclusionABCS mission aims at evaluating the overall system functionality (delivery of reagents, mixing of chemicals, LoC characterization, detection of emitted photons, readout noise, etc.) such as the chemicals and biomolecules stability (reagents and antibodies employed in the experiment) in the extremely harsh environment.The in-orbit validation of the proposed technology would represent a significant breakthrough for autonomous execution of bio-analytical experiments in space with potential application in search for signs of life in planetary exploration missions, space biolabs without human support, health monitoring in manned missions.

Introduction Astrobiology is an interdisciplinary field covered by only a few CubeSat missions so far. Moreover, no CubeSat mission has ever mounted miniaturized technology for the purpose of searching for molecular evidences of life in space. AstroBio CubeSat (ABCS) is a 3U CubeSat selected by the European Space Agency (ESA) to be launched in spring 2022 with the Vega C maiden flight, as piggy back passenger of the ASI LARES2 mission. ABCS will host a payload assembly based on Lab-on-Chip (LoC) technology for biomarkers detection and will be deployed along a circular orbit with altitude of about 5900 km and inclination of 7°, therefore crossing the inner Van Allen belt where the radiation flux is close to its maximum. Due to the harsh environment, ABCS payload and subsystems will be likely exposed to damages and degradations of electronics and performances, thus the payload assembly and the operational architecture were designed to be as much dependable as possible. This approach should constitute the first step to implement a mature technology with the aim to check the stability of chemicals and biomolecules involved in space experiments. This work reports an overview of ABCS architecture and the approach chosen for its operational design. ABCS Architecture ABCS objective is to test in space an automatic in-situ multiparameter LoC [1], which exploits luminol injection and enzymatic bio-mimicking assays on a functionalized 3D wax-printed origami. Luminol will be transported by capillarity to reaction sites with immobilized biomolecules targets where the reactions will trigger chemiluminescence, detected by means of hydrogenated amorphous silicon (a-Si:H) photodiodes deposited on a borosilicate glass substrate and connected to a photocurrent readout board [2]. The described payload consists in an experiment board hosting the LoC and a support board containing peristaltic pumps for luminol injection, drivers for pumps, radiation field effect transistors (RADFETs) and pressure/temperature sensors. The LoC architecture allows to repeat the experiment up to six times. In addition to RADFETs, ABCS mounts an ancillary radiation dose sensor (ARDS), developed by Thales Alenia Space, with the aim to assess the radiation effects. The ARDS is able to measure different amounts of current, until its failure, depending on the dose acquired. To mitigate the effects of the expected very high flux of charged particles, an extra tungsten layer shielding was mounted on each side panel and all the main subsystems (experiment and support board, batteries and EPS board, on-board computer (OBC), telemetry, tracking and control board), were placed inside a 5 mm thick aluminium box. At the same time, to keep the temperature range (from 4°C to 20°C) and operative pressure (about 1 atm) required to allow the LoC capillarity effect and to prevent reagents degradation, the box was sealed and a thermal control system, composed by a multi-layer insulation and an active heather mounted inside the box, was implemented. ABCS Mission Design ABCS will be deployed in an approximately circular orbit at about 5900 km altitude and 70° of inclination, spending a significant amount of the orbital period within the inner Van Allen belt, very close to its radiation peak point. ABCS ground operations will be mainly performed from the School of Aerospace Engineering (SIA) Ground Station. Simulations show that SIA will have access to ABCS 4 times a day, with an average duration of about 65 minutes. For this reason, a network of radioamateurs and third part ground stations will be involved for supporting the collection of the telemetry and science data packages and possibly uplink commands. ABCS Operations The assumption we made is that ABCS should be able to perform the payload operations in a completely autonomous manner. As we know, radiation flux will most likely induce several errors on electronics and performances, causing potential mission failure due to the fact that payload operations may not start because the OBC fails to send the command to start the experiment. A possible way to reduce failure is to perform ABCS experiments where the proton flux is lower. Simulations shows that this happens when ABCS is at polar latitudes, namely outside the range [-60°; 60°]. For this reason, the payload operations, based on redundant checks and triggers, were implemented accordingly. The purpose is to automatically determine if ABCS is at a latitude useful to perform the experiments and verifying this condition by means of multiple triggers, time or position based. Each trigger is used for scheduling purposes only if the ones with higher priority are unreliable. If all the triggers are not reliable, payload operations are forced to begin, as it is better to perform eventually degraded payload operations rather than performing no payload operations at all. Conclusions ABCS is required to operate in an extremely harsh environment where radiation fluxes are likely to degrade the electronic devices. Operations should be scheduled in order to reduce the time needed to perform all the experiments. The chosen approach will lead ABCS to complete the payload operations in three orbital periods, reducing the total ionizing dose absorbed and guaranteeing the higher system reliability. Acknowledgments ABCS AstroBio-CubeSat is supported by ASI - Italian Space Agency ASI/INAF Agreement n. 2019-30-HH.0. References [1] Iannascoli, L. et al. 2020, "Astrobio cubesat: Enabling technologies for astrobiology research in space", Proceedings of the International Astronautical Congress, IAC. [2] Mirasoli M, et al. 2014. Multiwell cartridge with integrated array of amorphous silicon photosensors for chemiluminescence detection: development, characterization and comparison with cooled-CCD luminograph. Anal Bioanal Chem. Sep;406(23):5645-56.

One of the main challenges to be faced in deep space missions is to protect the health and ensure the maximum efficiency of the crew by preparing methods of prevention and in situ diagnosis. Indeed, the hostile environment causes important health problems, ranging from muscle atrophy, osteopenia, and immunological and metabolic alterations due to microgravity, to an increased risk of cancer caused by exposure to radiation. It is, therefore, necessary to provide new methods for the real-time measurement of biomarkers suitable for deepening our knowledge of the effects of space flight on the balance of the immune system and for allowing the monitoring of the astronaut’s health during long-term missions. APHRODITE will enable human space exploration because it fills this void that affects both missions in LEO and future missions to the Moon and Mars. Its scientific objectives are the design, production, testing, and in-orbit demonstration of a compact, reusable, and reconfigurable system for performing the real-time analysis of oral fluid samples in manned space missions. In the frame of this project, a crew member onboard the ISS will employ APHRODITE to measure the selected target analytes, cortisol, and dehydroepiandrosterone sulfate (DHEA-S), in oral fluid, in four (plus one additional desired session) separate experiment sessions. The paper addresses the design of the main subsystems of the analytical device and the preliminary results obtained during the first implementations of the device subsystems and testing measurements on Earth. In particular, the system design and the experiment data output of the lab-on-chip photosensors and of the front-end readout electronics are reported in detail along with preliminary chemical tests for the duplex competitive CL-immunoassay for the simultaneous detection of cortisol and DHEA-S. Different applications also on Earth are envisaged for the APHRODITE device, as it will be suitable for point-of-care testing applications (e.g., emergency medicine, bioterrorism, diagnostics in developing countries, etc.).

Space exploration is facing a new era in view of the planned missions to the Moon and Mars. The development and the in-flight validation of new technologies, including analytical and diagnostic platforms, is pivotal for exploring and inhabiting these extreme environments. In this context, biosensors and lab-on-chip devices can play an important role in many situations, such as the analysis of biological samples for assessing the impact of deep space conditions on man and other biological systems, environmental and food safety monitoring, and the search of molecular indicators of past or present life in extra-terrestrial environments. Small satellites such as CubeSats are nowadays increasingly exploited as fast and low-cost platforms for conducting in-flight technology validation. Herein, we report the development of a fully autonomous lab-on-chip platform for performing chemiluminescence-based bioassays in space. The device was designed to be hosted onboard the AstroBio CubeSat nanosatellite, with the aim of conducting its in-flight validation and evaluating the stability of (bio)molecules required for bioassays in a challenging radiation environment. An origami-like microfluidic paper-based analytical format allowed preloading all the reagents in the dried form on the paper substrate, thus simplifying device design and analytical protocols, facilitating autonomous assay execution, and enhancing the stability of reagents. The chosen approach should constitute the first step to implement a mature technology with the aim to conduct life science research in space (e.g., for evaluation the effect of deep space conditions on living organisms or searching molecular evidence of life) more easily and at lower cost than previously possible.

Event Abstract Back to Event TISSUE REPAIR AND REGENERATION IN SPACE AND ON EARTH Monica Monici1*, Francesca Cialdai1, Michele Balsamo2, Liyana Popova2, Alessandro Donati2, Daniele Bani3, Paolo Romagnoli3, Jack J. Van Loon4 and Desire' Pantalone5 1 Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, Italy 2 Kayser (Italy), Italy 3 Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, Italy 4 Department of Oral and Maxillofacial Surgery/Oral Pathology, Medical Center, VU University Amsterdam, Netherlands 5 Department of Surgery and Translational Medicine, Careggi University Hospital, Italy Repair/regeneration is the process that makes organisms resilient to injuries (trauma, burns, accidental wounds, surgery), allowing survival, restoration of the protective barrier and organism integrity. Remarkable progress has been achieved in understanding the cellular and molecular mechanisms of tissue repair, but many of them still remain elusive and many questions are unanswered. For example, it remains unexplained why mammals have a tendency for imperfect healing and scarring, rather than full regeneration. Also the causes of failure in tissue repair mechanisms are poorly understood and currently the available therapies are limited [Eming et al., 2014]. It is known that wound healing is a complex set of processes, involving a number of cell lineages. Alterations in one or more of these events, that overlap and intertwine, result in defective repair, ranging from delayed healing and chronic ulcers to scarring and fibrosis. The different steps of tissue repair are regulated by a multitude of biochemical and physical factors, including gravitational/mechanical forces acting at cellular and tissue level. Moreover, several factors related to the state of patients and operative modalities are important for tissue repair and its complications: age, gender, overweight, systemic diseases (e.g. diabetes), wound contamination, non-physiological environment, urgency, emergency care, wound care, suturing materials and techniques. On Earth, traumatic injury is a major cause of mortality and disability. In addition, millions of surgical wounds are performed annually in the course of routine surgery and medical care. Therefore, defective or delayed wound healing, chronic ulcers and fibrosis are important health and socio-economic problems [Sen et al., 2009]. They are caused by alterations mechanisms underlying repair, such as dysregulated immune function, chronic inflammation, impaired fibroblast function, defective ECM deposition, altered endothelial function, dysregulated apoptosis, etc... Until now wound healing has not been considered as a major health problem in space because, during the current space missions, the occurrence of injuries, traumatic events and surgical emergencies has been considered unlikely. Despite the current considerations, future space exploration programs require long duration missions beyond LEO and hence health emergencies on board cannot be excluded, while medical evacuation times to Earth might become too long and the communication lag would render useless to guide the crew actions remotely. Therefore, medical care planning for future exploration missions should consider emergency surgery and trauma care, and meanwhile studies on repair processes in space are of paramount importance as wound healing is critical to survive trauma or surgery. Results of our previous studies, in agreement with those of other authors, showed microgravity-induced changes in mechanisms underlying tissue repair [Monici et al., 2011; Cialdai et al., 2017]. Experiments performed in real and simulated microgravity revealed alterations in fibroblast and endothelial cell function, changes in ECM production and dysregulation in apoptosis. Interestingly, in astronauts, deficient immune function, signs of chronic inflammation and insulin-resistance have been observed. These alterations, resembling some features of systemic diseases which impair wound healing on Earth, could affect the body’s response to injury and could represent a model to study defective healing mechanisms [Demontis et al., 2017]. The experiment “Wound Healing and Sutures in Unloading Conditions”, selected by ESA (ILSRA-2014-0043), aims to study the behavior of “in vitro” sutured wound models in weightlessness (ISS). The findings are expected to increase the knowledge on wound healing in weightlessness, suggest new pathways for tissue engineering, give cues for strategies promoting tissue repair/regeneration and improving the management of defective healing in space and on Earth. The on-ground activities carried out in preparation of the experiment can be summarized as follows: 1) standardization of procedures for biopsy collection, model preparation, techniques for model culture and postflight analysis; 2) improvement of culture techniques to ensure tissue survival throughout the experiment; 3) analysis of tissue mechanical properties and development of a device to model physiological tensile strength in the tissue and measure its changes due to suture behavior and the healing process. The sutured wound models developed for the experiment are based on skin and vein vessel biopsies cultured on dedicated hardware, in conditions that ensure their survival for over 3 weeks and allow to stretch the tissue, mimicking the physiological tensional strength, and monitor tension changes due to suture application and repair process at the wound site. Hence, not only histological and biochemical aspects, but also the biomechanical properties of sutured wounds can be analyzed. For the in-flight experiment, after collection biopsies are maintained in modified, RPMI-based, organ culture medium at 4°C for storage and travelling to the launch site. Here, linear wounds are performed on skin by a scalpel and then sutured. The vessels are completely divided to perform an end-to-end vascular anastomosis. RPMI-based medium is replaced with modified, DMEM-based, organ culture medium. On the ISS the sutured wound models will be placed at 32°C for activation of repair mechanisms and then frozen at different time-points. During the experiment, the tensile strength in tissues will be monitored and morphological imaging of the sutured wounds is performed. In order to obtain information on the activation of tissue repair mechanism in weightlessness, post-flight analysis is scheduled to study: suture morphology and ultrastructure (histology and electron microscopy); proteomics on membrane microdomains, gene expression profile, extracellular matrix turnover, apoptosis and necrosis, markers of repair mechanism activation, fibroblast behavior, stiffness and strength in sutured tissues. Beyond the development of the sutured wound models, their survival for a sufficient amount of time (at least 3 weeks) has been identified as a crucial point for the success of the experiment. Focusing on this problem, we developed a tissue culture technique based on tissue stretching and modification of organ culture media by adding proangiogenic substances and peptides. In addition to defining the requirements for the in-flight experiment, the on-ground activity has produced a significant result: this technique, which allows the survival of the tissue biopsies for over 3 weeks (Fig 1), can be applied also on ground in tissue culture and engineering for transplantation and regeneration, studies on tissue mechanical properties, studies for improvement of surgical techniques and materials. FIGURE LEGEND: Fig 1 – Skin samples cultured for over 3 weeks in common culture conditions (A) and using the culture technique developed for the in-flight experiment (B), which allows a better survival and preservation of the tissue. Figure 1 Acknowledgements This study was performed with the support of Italian Space Agency (RITMI ASI N. 2013-090-R.O; ASI 2018-14-U.O Suture in Space) References Cialdai F, Vignali L, Morbidelli L, Colciago A, Celotti F, Santi A, Caselli A, Cirri P, Monici M. Modeled Microgravity Affects Fibroblast Functions Related to Wound Healing. Microgravity Sci. Technol. 2017, DOI 10.1007/s12217-016-9532-7 - Demontis GC, Germani MM, Caiani EG, Barravecchia I, Passino C, Angeloni D. Human Pathophysiological Adaptations to the Space Environment. Front Physiol. 2017 Aug 2;8:547. doi: 10.3389/fphys.2017.00547. -Eming SA, Martin P, Tomic-Canic M. Wound repair and regeneration: Mechanisms, signaling, and translation. Science Translational Medicine, 6: 265-271, 2014, DOI: 10.1126/scitranslmed.3009337. -Monici M, Cialdai F, Romano G, Fusi F, Egli M, Pezzatini S, Morbidelli L. An in vitro study on tissue repair: impact of unloading on cells involved in the remodelling phase. Microgravity, Sci Technol., vol. 23, p. 391-401, 2011. ISSN: 0938-0108, doi: 10.1007/s12217-011-9259-4 -Sen CK, Gordillo GM, Roy S, Kirsner R, Lambert L, Hunt TK, Gottrup F, Gurtner GC, Longaker MT. Human skin wounds: A major and snowballing threat to public health and the economy. Wound Repair Regen. 17, 763–771, 2009. Keywords: Wound Healing, Trauma care, Emergency surgery, Sutures, Microgravity (μg), Tissue repair and regeneration Conference: 39th ISGP Meeting & ESA Life Sciences Meeting, Noordwijk, Netherlands, 18 Jun - 22 Jun, 2018. Presentation Type: Extended abstract Topic: Astronaut health Citation: Monici M, Cialdai F, Balsamo M, Popova L, Donati A, Bani D, Romagnoli P, Van Loon JJ and Pantalone D (2019). TISSUE REPAIR AND REGENERATION IN SPACE AND ON EARTH. Front. Physiol. Conference Abstract: 39th ISGP Meeting & ESA Life Sciences Meeting. doi: 10.3389/conf.fphys.2018.26.00034 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Dec 2018; Published Online: 16 Jan 2019. * Correspondence: Dr. Monica Monici, Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, Florence, Italy, monica.monici@unifi.it Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Monica Monici Francesca Cialdai Michele Balsamo Liyana Popova Alessandro Donati Daniele Bani Paolo Romagnoli Jack J Van Loon Desire' Pantalone Google Monica Monici Francesca Cialdai Michele Balsamo Liyana Popova Alessandro Donati Daniele Bani Paolo Romagnoli Jack J Van Loon Desire' Pantalone Google Scholar Monica Monici Francesca Cialdai Michele Balsamo Liyana Popova Alessandro Donati Daniele Bani Paolo Romagnoli Jack J Van Loon Desire' Pantalone PubMed Monica Monici Francesca Cialdai Michele Balsamo Liyana Popova Alessandro Donati Daniele Bani Paolo Romagnoli Jack J Van Loon Desire' Pantalone Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Background and Aims Root soil penetration and path optimization are fundamental for root development in soil. We describe the influence of soil strength on root elongation rate and diameter, response to gravity, and root-structure tortuosity, estimated by average curvature of primary maize roots. Methods Soils with different densities (1·5, 1·6, 1·7 g cm-3), particle sizes (sandy loam; coarse sand mixed with sandy loam) and layering (monolayer, bilayer) were used. In total, five treatments were performed: Mix_low with mixed sand low density (three pots, 12 plants), Mix_medium - mixed sand medium density (three pots, 12 plants), Mix_high - mixed sand high density (three pots, ten plants), Loam_low sandy loam soil low density (four pots, 16 plants), and Bilayer with top layer of sandy loam and bottom layer mixed sand both of low density (four pots, 16 plants). We used non-invasive three-dimensional magnetic resonance imaging to quantify effects of these treatments. Key Results Roots grew more slowly [root growth rate (mm h-1); decreased 50 %] with increased diameters [root diameter (mm); increased 15 %] in denser soils (1·7 vs. 1·5 g cm-3). Root response to gravity decreased 23 % with increased soil compaction, and tortuosity increased 10 % in mixed sand. Response to gravity increased 39 % and tortuosity decreased 3 % in sandy loam. After crossing a bilayered-soil interface, roots grew more slowly, similar to roots grown in soil with a bulk density of 1·64 g cm-3, whereas the actual experimental density was 1·48±0·02 g cm-3. Elongation rate and tortuosity were higher in Mix_low than in Loam_low. Conclusions The present study increases our existing knowledge of the influence of physical soil properties on root growth and presents new assays for studying root growth dynamics in non-transparent media. We found that root tortuosity is indicative of root path selection, because it could result from both mechanical deflection and active root growth in response to touch stimulation and mechanical impedance.

Living roots grow in soil, which is a heterogeneous environment containing a wide variety of physical barriers. Roots must avoid these barriers to grow: first, they adopt a characteristic S-shape that can be described by the angle between the root tip and the barrier (i.e., the tip-to-barrier angle); then, they move parallel to the barrier by keeping the sensitive tip in contact with the barrier until it has been circumvented. We investigated this avoidance response in the primary roots of maize (Zea mays) by considering flat barriers oriented at 45, 60 and 90 degrees with respect to the gravity vector. We measured the root tip orientation during growth by using time-lapse imaging and specially developed tip-tracking software (9 trials for each value of the barrier orientation). Remarkably, we found that the S-shapes formed by the roots were characterized by the same tip-to-barrier angle regardless of the barrier orientation: namely, 21.96 ± 2.97, 21.48 ± 4.75 and 20.81 ± 9.39 degrees for barriers oriented at 45, 60 and 90 degrees, respectively. We also considered the root growth after bypassing the barrier; for the barrier at 90 degrees, we observed a gravitropic recovery. Furthermore, we used a mathematical model to quantify the characteristic time of S-shape formation (95 min on average) and gravitropic recovery (approximately 42 min); the obtained values are consistent with those of previous studies. Our results suggest that the avoidance response develops with respect to a reference frame associated with the barrier. From a biological viewpoint, the reason the root adopts the specifically observed tip-to-barrier angle is unclear, but we speculate that maize root optimizes energy expenditure during the penetration of a medium.

Moving in an unstructured environment such as soil requires approaches that are constrained by the physics of this complex medium and can ensure energy efficiency and minimize friction while exploring and searching. Among living organisms, plants are the most efficient at soil exploration, and their roots show remarkable abilities that can be exploited in artificial systems. Energy efficiency and friction reduction are assured by a growth process wherein new cells are added at the root apex by mitosis while mature cells of the root remain stationary and in contact with the soil. We propose a new concept of root-like growing robots that is inspired by these plant root features. The device penetrates soil and develops its own structure using an additive layering technique: each layer of new material is deposited adjacent to the tip of the device. This deposition produces both a motive force at the tip and a hollow tubular structure that extends to the surface of the soil and is strongly anchored to the soil. The addition of material at the tip area facilitates soil penetration by omitting peripheral friction and thus decreasing the energy consumption down to 70% comparing with penetration by pushing into the soil from the base of the penetration system. The tubular structure provides a path for delivering materials and energy to the tip of the system and for collecting information for exploratory tasks.

Soil penetration strategies of plant roots can represent an interesting source of inspiration for designing explorer robots. In this work we present a selection of these strategies whose performances were discussed and evaluated by means of engineering mock-ups and dedicated experiments in granular substrates. The obtained results demonstrated that root elongation from the tip reduces the forces needed for soil penetration up to 50%; tip morphology and anchorage resulted to strongly influence penetration performances.

Plant roots are a new paradigm for soft robotics. Study of embodied behavior in roots may lead to the implementation of movements guided by structural deformations and to the use of sensors and actuators as body parts. In this work the obstacle avoidance in roots and its interplay with the gravitropism were studied both from biological and robotic viewpoint. Living roots resulted to achieve the maximum pushing force on an obstacle before starting circumnavigation (30 mN in 100 min), thus indicating the existence of a triggering threshold. Tip-to-obstacle angle (20°) was not influenced by the gravity. A robotic mockup capable to bend like living roots was build on the basis of current knowledge and our results on obstacle avoidance behavior. Exploitation of morphological features and passive body deformation resulted to be useful for implementing a simplified control of the robot during gravitropism and obstacle avoidance.

The growth process of roots consists of many activities, such as exploring the soil volume, mining minerals, avoiding obstacles and taking up water to fulfil the plant's primary functions, that are performed differently, depending on environmental conditions. Root movements are strictly related to a root decision strategy, which helps plants to survive under stressful conditions by optimizing energy consumption. In this work, we present a novel image-analysis tool to study the kinematics of the root tip (apex), named analyser for root tip tracks (ARTT). The software implementation combines a segmentation algorithm with additional software imaging filters in order to realize a 2D tip detection. The resulting paths, or tracks, arise from the sampled tip positions through the acquired images during the growth. ARTT allows work with no markers and deals autonomously with new emerging root tips, as well as handling a massive number of data relying on minimum user interaction. Consequently, ARTT can be used for a wide range of applications and for the study of kinematics in different plant species. In particular, the study of the root growth and behaviour could lead to the definition of novel principles for the penetration and/or control paradigms for soil exploration and monitoring tasks. The software capabilities were demonstrated by experimental trials performed with Zea mays and Oryza sativa.

In this paper we propose a soil penetration robotic system inspired by low friction penetration strategies in plant roots. Growth of cells at the root tip deforms soil, while sloughing cells in the cap create an interface between root and soil to reduce root-soil friction during penetration. A simple prototype, inspired by these root features and based on a tubular shaft and a soft continuum skin, was developed. The skin is kept inside the shaft and slips out and slides on its external body. This outward movement of the skin opens the soil in front of the tip and helps the system to penetrate. The skin covering the external body of shaft imitates the role of sloughing cells and provides low-friction interface between soil and shaft. Interaction between the external skin and soil gives to the system self-anchorage capabilities for the penetration. The performances of our robotic system were characterized during penetration in granular soils. The skin-soil interaction was found to be fundamental for 1) displacing the soil in front of the tip and 2) preventing backward movements of the robot by anchoring the posterior body to the soil. In order to exploit these effects some artificial hairs were added along the skin. The increased hair density (0.012 hairs/mm2) resulted in higher penetration depth of robot (about 30%).

Studying plant root kinematics is important for understanding certain aspects of root growth and movement, which are strictly correlated in plants. However, there is little available data on autonomous movements in plant roots, such as nutations, and the data that are available are poorly described. We investigated the autonomous movements during growth in primary maize roots by estimating the main kinematic parameters of nutations (i.e., the period of duration and amplitude) and the growth rate. The estimations of nutation parameters were performed by developing dedicated methods, which are based on the analysis of root tip displacement and tip velocity. The data relative to the tip displacements were obtained using tip tracing software developed by our team specifically for this purpose. The results confirmed that the nutational phenomenon covers the continuous range of periods and amplitudes, with certain dominant period-amplitude types, which we clustered into three groups: i) amplitudes less than 0.1 mm and 4–16 min periods, ii) amplitudes less than 0.1 mm and 20–120 min periods, and iii) amplitudes greater than 0.1 mm and 24–120 min periods.

Plant roots represent an amazing source of inspiration for designing and developing dexterous, branching robots capable of efficient soil exploration in various scenarios, from environmental monitoring to space exploration. The natural roots, in fact, have optimally evolved to efficiently penetrate and move into the soil. In this work, starting from the study of the plant roots penetration capabilities, we defined the optimal tip shape and the penetration rate of a robotic root apex, by evaluating the penetration resistance to different types of granular substrates. The results showed that the conical and parabolic tips with a pointed shape, similar to the apex tip of the living roots, are more efficient in terms of penetration resistance. The penetration resistance of the robotic root apex results similar to that observed in natural roots. Moreover, we identified the optimal penetration rate of the root-like robotic system as 40 mm/min.