A Mission Simulating the Search for Life on Mars with Automated Drilling, Sample Handling, and Life Detection Instruments Performed in the Hyperarid Core of the Atacama Desert, Chile.

We report on a field demonstration of a rover-based drilling mission to search for biomolecular evidence of life in the arid core of the Atacama Desert, Chile. The KREX2 rover carried the Honeybee Robotics 1 m depth The Regolith and Ice Drill for Exploration of New Terrains (TRIDENT) drill and a robotic arm with scoop that delivered subsurface fines to three flight prototype instruments: (1) The Signs of Life Detector (SOLID), a protein and biomolecule analyzer based on fluorescence sandwich microarray immunoassay; (2) the Planetary In Situ Capillary Electrophoresis System (PISCES), an amino acid analyzer based on subcritical water extraction coupled to microchip electrophoresis analysis; and (3) a Wet Chemistry Laboratory cell to measure soluble ions using ion selective electrodes and chronopotentiometry. A California-based science team selected and directed drilling and sampling of three sites separated by hundreds of meters that included a light-toned basin area showing evidence of aqueous activity surrounded by a rocky desert pavement. Biosignatures were detected in basin samples collected at depths ranging from 20 to 80 cm but were not detected in the surrounding area. Subsurface stratigraphy of the units drilled was interpreted from drill sensor data as fine-scale layers of sand/clay sediments interspersed with layers of harder material in the basins and a uniform subsurface composed of course-to-fine sand in the surroundings. The mission timeline and number of commands sent to accomplish each activity were tracked. The deepest sample collected (80 cm) required 55 commands, including drilling and delivery to three instruments. Elapsed time required for drilling and sample handling was less than 3 hours to collect sample from 72 cm depth, including time devoted to recovery from a jammed drill. The experiment demonstrated drilling, sample transfer technologies, and instruments that accomplished successful detection of biomolecular evidence of life in one of the most biologically sparse environments on Earth.

Scientific exploration of challenging planetary analog environments with a team of legged robots.

The interest in exploring planetary bodies for scientific investigation and in situ resource utilization is ever-rising. Yet, many sites of interest are inaccessible to state-of-the-art planetary exploration robots because of the robots' inability to traverse steep slopes, unstructured terrain, and loose soil. In addition, current single-robot approaches only allow a limited exploration speed and a single set of skills. Here, we present a team of legged robots with complementary skills for exploration missions in challenging planetary analog environments. We equipped the robots with an efficient locomotion controller, a mapping pipeline for online and postmission visualization, instance segmentation to highlight scientific targets, and scientific instruments for remote and in situ investigation. Furthermore, we integrated a robotic arm on one of the robots to enable high-precision measurements. Legged robots can swiftly navigate representative terrains, such as granular slopes beyond 25°, loose soil, and unstructured terrain, highlighting their advantages compared with wheeled rover systems. We successfully verified the approach in analog deployments at the Beyond Gravity ExoMars rover test bed, in a quarry in Switzerland, and at the Space Resources Challenge in Luxembourg. Our results show that a team of legged robots with advanced locomotion, perception, and measurement skills, as well as task-level autonomy, can conduct successful, effective missions in a short time. Our approach enables the scientific exploration of planetary target sites that are currently out of human and robotic reach.

A gravity-independent single-phase electrode reservoir for capillary electrophoresis applications.

Capillary electrophoresis (CE) holds great promise as an in situ analytical technique for a variety of applications. However, typical instrumentation operates with open reservoirs (e.g., vials) to accommodate reagents and samples, which is problematic for automated instruments designed for space or underwater applications that may be operated in various orientations. Microgravity conditions add an additional challenge due to the unpredictable position of the headspace (air layer above the liquid) in any two-phase reservoir. One potential solution for these applications is to use a headspace-free, flow-through reservoir design that is sealed and connected to the necessary reagents and samples. Here, we demonstrate a flow-through high-voltage (HV) reservoir for CE that is compatible with automated in situ exploration needs, and which can be electrically isolated from its source fluidics (in order to prevent unwanted leakage current). We also demonstrate how the overall system can be rationally designed based on the operational parameters for CE to prevent electrolysis products generated at the electrode from entering the capillary and interfering with the CE separation. A reservoir was demonstrated with a 19 mm long, 1.8 mm inner diameter channel connecting the separation capillary and the HV electrode. Tests of these reservoirs integrated into a CE system show reproducible CE system operation with a variety of background electrolytes at voltages up to 25 kV. Rotation of the reservoirs, and the system, showed that their performance was independent of the direction of the gravity vector.

Providing Enhanced Migration Time Reproducibility with a High-Voltage-Compatible Flow Sensor for Capillary Electrophoresis.

In capillary electrophoresis (CE), analyte identification is primarily based on migration time, which is a function of the analyte's electrophoretic mobility and the electro-osmotic flow (EOF). The migration time can be impacted by the presence of parasitic flow from changes in temperature or pressure during the run. Presented here is a high-voltage-compatible flow sensor capable of monitoring the volumetric flow inside the capillary during a separation with nL/min resolution. The direct measurement of both flow and time allows for compensation of flow instabilities. By expressing the electropherogram in terms of signal versus electromigration velocity instead of time, it is possible to improve the run-to-run reproducibility up to 25×.

Open-source lab hardware: A versatile microfluidic control and sensor platform.

Here we describe a completely integrated and customizable microfluidic control and sensing architecture that can be readily implemented for laboratory or portable chemical or biological control and sensing applications. The compact platform enables control of 32 solenoid valves, a multitude of pumps and motors, a thermo-electric controller, a pressure controller, and a high voltage power supply. It also features two temperature probe interfaces, one relative humidity and ambient temperature sensor, two pressure sensors, and interfaces to an electrical conductivity sensor, flow sensor, and a bubble detector. The platform can be controlled via an onboard microcontroller and requires no proprietary software.

Open-source lab hardware: Driver and temperature controller for high compliance voltage, fiber-coupled butterfly lasers.

This article describes the development of a compact, relatively low-cost, high compliance voltage laser driver that can provide the constant optical laser output required for a range of applications. The system contains an integrated, high-precision temperature controller that can be implemented with butterfly-style lasers containing an internal thermoelectric cooler. The laser parameters can be controlled manually or via an onboard microcontroller. Additionally, an adjustable over-current protection circuit safeguards the laser diode from potential damage.

Open-source lab hardware: Low noise adjustable two-stage gain transimpedance amplifier with DC offset for low-light detection.

An open-source, low noise, low cost, and tunable transimpedance amplifier is presented. The compact circuit board requires few parts and costs less than $65 USD. The transimpedance amplifier is intended for low-light detection and operation with commercial photomultiplier tubes (PMTs). It provides a much more cost-effective acquisition tool compared to competitive products on the market. The system can easily be assembled and modified to suit specific current sensing applications. The amplifier features two variable gains and an adjustable DC offset to optimize dynamic range and suppress potential bias in the signal. With a target bandwidth of DC to 2 Hz and fourth-order Sallen-Key cutoff, the design is ideally suited for various applications in the field of analytical chemistry and biology, such as laser-induced fluorescence detection or chemiluminescence measurements.

Fully Automated Microchip Electrophoresis Analyzer for Potential Life Detection Missions.

There are a variety of complementary observations that could be used in the search for life in extraterrestrial settings. At the molecular scale, patterns in the distribution of organics could provide powerful evidence of a biotic component. In order to observe these molecular biosignatures during spaceflight missions, it is necessary to perform separation science in situ. Microchip electrophoresis (ME) is ideally suited for this task. Although this technique is readily miniaturized and numerous instruments have been developed over the last 3 decades, to date, all lack the automation capabilities needed for future missions of exploration. We have developed a portable, automated, battery-powered, and remotely operated ME instrument coupled to laser-induced fluorescence detection. This system contains all the necessary hardware and software interfaces for end-to-end functionality. Here, we report the first application of the system for amino acid analysis coupled to an extraction unit in order to demonstrate automated sample-to-data operation. The system was remotely operated aboard a rover during a simulated Mars mission in the Atacama Desert, Chile. This is the first demonstration of a fully automated ME analysis of soil samples relevant to planetary exploration. This validation is a critical milestone in the advancement of this technology for future implementation on a spaceflight mission.

Self-referenced waveguide grating sensor.

Like any other sensor system, performances of waveguide grating couplers are affected by adverse effects such as noise and drift, mainly limiting the devices' resolution and long-term stability. It is therefore often required to reference the measurement with a secondary, parallel sensor to decrease these undesired influences. Here we present a simple but effective method to self-reference a label-free waveguide grating coupler by partially coating and thereby passivating the sensitive area with an inert layer. The presented waveguide grating chip design offers the advantage of internal self-referencing for adverse effects, such as inherent system instabilities, mechanical disturbance, or temperature drift, without the need of a sacrificial reference channel.

A Simple Method for Automated Solid Phase Extraction of Water Samples for Immunological Analysis of Small Pollutants.

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and enables to perform rapid, automated and simple SPE. The pre-concentrated solution is compatible with analysis by immunoassay, with a low organic solvent content. A method is described for the extraction and pre-concentration of natural hormone 17ß-estradiol in 100 ml water samples. Reverse phase SPE is performed with octadecyl-silica sorbent and elution is done with 200 µl of methanol 50% v/v. Eluent is diluted by adding di-water to lower the amount of methanol. After preparing manually the SPE column, the overall procedure is performed automatically within 1 hr. At the end of the process, estradiol concentration is measured by using a commercial enzyme-linked immune-sorbent assay (ELISA). 100-fold pre-concentration is achieved and the methanol content in only 10% v/v. Full recoveries of the molecule are achieved with 1 ng/L spiked de-ionized and synthetic sea water samples.

Experimental Validation of the Sensitivity of Waveguide Grating Based Refractometric (Bio)sensors.

Despite the fact that the theoretical foundations of the sensitivity of waveguide grating based (bio)sensors are well-known, understood and their implications anticipated by the scientific community since several decades, to our knowledge, no prior publication has experimentally confirmed waveguide sensitivity for multiple film thicknesses, wavelengths and polarization of the propagating light. In this paper, the bulk refractive index sensitivity versus waveguide thickness of said refractometric sensors is experimentally determined and compared with predictions based on established theory. The effective refractive indices and the corresponding sensitivity were determined via the sensors' coupling angles at different cover refractive indices for transverse electric as well as transverse magnetic polarized illumination at various wavelengths in the visible and near-infrared. The theoretical sensitivity was calculated by solving the mode equation for a three layer waveguide.

Automated and portable solid phase extraction platform for immuno-detection of 17ß-estradiol in water.

A fully automated and portable system for solid phase extraction (SPE) has been developed for the analysis of the natural hormone 17ß-estradiol (E2) in environmental water by enzyme linked immuno-sorbent assay (ELISA). The system has been validated with de-ionized and artificial sea water as model samples and allowed for pre-concentration of E2 at levels of 1, 10 and 100 ng/L with only 100 ml of sample. Recoveries ranged from 24±3% to 107±6% depending on the concentration and sample matrix. The method successfully allowed us to determine the concentration of two seawater samples. A concentration of 15.1±0.3 ng/L of E2 was measured in a sample obtained from a food production process, and 8.8±0.7 ng/L in a sample from the Adriatic Sea. The system would be suitable for continuous monitoring of water quality as it is user friendly, and as the method is reproducible and totally compatible with the analysis of water sample by simple immunoassays and other detection methods such as biosensors.

Integrated planar optical waveguide interferometer biosensors: a comparative review.

Integrated planar optical waveguide interferometer biosensors are advantageous combinations of evanescent field sensing and optical phase difference measurement methods. By probing the near surface region of a sensor area with the evanescent field, any change of the refractive index of the probed volume induces a phase shift of the guided mode compared to a reference field typically of a mode propagating through the reference arm of the same waveguide structure. The interfering fields of these modes produce an interference signal detected at the sensor׳s output, whose alteration is proportional to the refractive index change. This signal can be recorded, processed and related to e.g. the concentration of an analyte in the solution of interest. Although this sensing principle is relatively simple, studies about integrated planar optical waveguide interferometer biosensors can mostly be found in the literature covering the past twenty years. During these two decades, several members of this sensor family have been introduced, which have remarkably advantageous properties. These entail label-free and non-destructive detection, outstandingly good sensitivity and detection limit, cost-effective and simple production, ability of multiplexing and miniaturization. Furthermore, these properties lead to low reagent consumption, short analysis time and open prospects for point-of-care applications. The present review collects the most relevant developments of the past twenty years categorizing them into two main groups, such as common- and double path waveguide interferometers. In addition, it tries to maintain the historical order as it is possible and it compares the diverse sensor designs in order to reveal not only the development of this field in time, but to contrast the advantages and disadvantages of the different approaches and sensor families, as well.

Optimal hybridization efficiency upon immobilization of oligonucleotide double helices.

For the first time, the covalent immobilization of oligonucleotides double helices onto surfaces prior to sequential denaturation and rehybridization is proven to lead to optimal hybridization efficiency. Two indirect methods were used for monitoring these reactions in situ: the quartz crystal microbalance with dissipation monitoring (QCM-D) and the wavelength interrogated optical sensor (WIOS, Bright Reader). Both techniques led to the result that with this immobilization approach one could reach nearly 100% hybridization efficiency. Moreover, applying the polymer theory to the adsorption of nucleotide sequences onto surfaces, we demonstrate, that for single stranded sequences the coil conformation prevails over the stretch one.