Since its inception, the femtosatellite has developed into a complex and capable spacecraft. However, despite such advances the implementation of predicted applications remains elusive. In response, this paper explores three femtosatellite mission architectures, the drone, swarm, and hive, to characterize what possible femtosatellite mission could be envisioned for true space applications. Starting from a single femtosatellite, each architecture represents an increase in network complexity, so the use of graph theory is proposed as a means for characterizing, understanding, and modelling femtosatellite systems. A simple reliability model is also proposed for each of the mission architectures, and a simulation is carried out to generate a profile of the system's lifecycle. The results are discussed for each of the architectures in relation to potential applications. Each of the architectures was shown to be feasible for short duration missions due to the inherent unreliability of femtosatellites. Additionally, mid- and long-duration missions were shown to be possible for swarms and hives with sufficiently large populations. Finally, applications are re-examined considering the lifecycle profile exhibited by each system.

This paper is an exploration of how massively distributed femtosatellite networks can be implemented in space missions aimed at modelling the space environment for variables that show both time and space dependence. A theory of distributed sensing for space-time deconvolution is presented and performance parameters for system evaluation are described. Measurement of the magnetic field in low Earth orbit, in the presence of field perturbations, is selected as a case study for demonstrating the concept in simulation. A femtosatellite swarm, designed for the simulated space environment, shows the capability of space-time deconvolution in sensing. From the simulated mission, challenges in the design and deployment of free-flying sensor swarms, especially in the femtosatellite mass range, are identified and discussed.

The utility of distributed magnetic torque rods for the attitude control of a large space structure is investigated. Distributed arrays of actuators offer advantages such as distributing structural loads, increasing fault tolerance, allowing structures to be designed modularly, and additionally the actuators may be integrated with on-orbit fabrication strategies. First, distributed torques are shown to effectively rotate highly flexible structures. This is compared with torques applied to the centre-of-mass of the structure, which cause large surface deformations and can fail to enact a rotation. This is demonstrated using a spring-mass model of a planar structure with embedded actuators. A distributed torque algorithm is then developed to control an individually addressable array of actuators. Attitude control simulations are performed, using the array to control a large space structure, again modelled as a spring-mass system. The attitude control system is demonstrated to effectively detumble a representative 75 x 75 m flexible structure, and perform slew manoeuvres, in the presence of both gravity-gradient torques and a realistic magnetic field model.

In-orbit relative navigation between a networked swarm of centimeter-scale femto-spacecraft would add considerable value to a range of space mission concepts and applications, such as for multipoint sensing and distributed sparse aperture interferometry. For a swarm of networked femto-spacecraft, relative position determination would be possible by inferring coarse range estimates from the received signal strength indication associated with the communication link between swarm members. This is particularly advantageous for highly resource-constrained devices. In this paper, algorithms for swarm relative positioning using interspacecraft range estimates are presented that can be applied to centralized, decentralized, and distributed network configurations. Relative navigation filters for initial relative orbit determination and state estimation are presented for femto-spacecraft swarm deployment and dispersal scenarios. The algorithms presented could also find use in terrestrial applications, in static and dynamic wireless sensor networks.

There is a global unmet need for rapid and cost-effective prognostic and diagnostic tools that can be used at the bedside or in the doctor’s office to reduce the impact of serious disease. Many cancers are diagnosed late, leading to costly treatment and reduced life expectancy. With prostate cancer, the absence of a reliable test has inhibited the adoption of screening programs. We report a microelectronic point-of-care metabolite biomarker measurement platform and use it for prostate cancer detection. The platform, using an array of photodetectors configured to operate with targeted, multiplexed, colorimetric assays confined in monolithically integrated passive microfluidic channels, completes a combined assay of 4 metabolites in a drop of human plasma in under 2 min. A preliminary clinical study using l-amino acids, glutamate, choline, and sarcosine was used to train a cross-validated random forest algorithm. The system demonstrated sensitivity to prostate cancer of 94% with a specificity of 70% and an area under the curve of 0.78. The technology can implement many similar assay panels and hence has the potential to revolutionize low-cost, rapid, point-of-care testing.

A mission scenario is proposed, where a large number of centimeter-scale femto-spacecraft are dispersed from a CubeSat piggyback payload on a future Mars mission. This swarm would deliver real-time massively parallel sensing throughout entry, descent, and landing with in-orbit measurements, atmospheric characterization during descent, and even surface science upon landing. Because few entry profiles exist at present for the in situ atmospheric modeling of Mars, a ChipSat swarm offers a promising tool for cost-effective atmospheric characterization that could lower risks for ongoing Mars exploration programs.

We demonstrate a proof of concept highly miniaturised fluorescence imager and its application to detecting cancer in resected human colon cancer tissues. Fluorescence imaging modalities have already been successfully implemented in traditional endoscopy. However, the procedure still causes discomfort and requires sedation. Wireless fluorescence capsule endoscopy has the potential to improve diagnostic accuracy with less inconvenience for patients. In this paper we present a 5 mm × 6 mm × 5 mm optical block that is small enough to integrate into a capsule endoscope. The block integrates ultrathin filters for optical isolation and was successfully integrated with a sensitive CMOS SPAD array to detect green fluorescence from Flavin Adenine Dinucleotide (FAD), which is an endogenous fluorophore responsible for autofluorescence in human tissues, and fluorescence from the cancer selective molecular probe ProteoGREENTM-gGlu used to label colorectal cancer cells. In vitro studies were validated using a commercial ModulusTM Microplate reader. The potential use of the device in capsule endoscopy was further validated by imaging healthy and malignant resected human tissues from the colon to detect changes in autofluorescence signal that are crucial for cancer diagnosis.

An important consideration when scaling semiconductor sensor devices is the effect it may have on noise performance. Overall signal to noise ratio can be improved both by increasing sensor size, or alternatively by averaging the signal from two or more smaller sensors. In the design of sensor systems it is not immediately clear which is the best strategy to pursue. In this paper, we present a detailed theoretical and experimental study based on three different sensor arrays that show that an array of small independent sensors is always less noisy than a large sensor of the same size. (C) 2019 The Authors. Published by Elsevier Ltd.

Precision metabolomics and quantification for cost-effective rapid diagnosis of disease are the key goals in personalized medicine and point-of-care testing. At present, patients are subjected to multiple test procedures requiring large laboratory equipment. Microelectronics has already made modern computing and communications possible by integration of complex functions within a single chip. As More than Moore technology increases in importance, integrated circuits for densely patterned sensor chips have grown in significance. Here, we present a versatile single complementary metal-oxide-semiconductor chip forming a platform to address personalized needs through on-chip multimodal optical and electrochemical detection that will reduce the number of tests that patients must take. The chip integrates interleaved sensing subsystems for quadruple-mode colorimetric, chemiluminescent, surface plasmon resonance, and hydrogen ion measurements. These subsystems include a photodiode array and a single photon avalanche diode array with some elements functionalized to introduce a surface plasmon resonance mode. The chip also includes an array of ion sensitive field-effect transistors. The sensor arrays are distributed uniformly over an active area on the chip surface in a scalable and modular design. Bio-functionalization of the physical sensors yields a highly selective simultaneous multiple-assay platform in a disposable format. We demonstrate its versatile capabilities through quantified bio-assays performed on-chip for glucose, cholesterol, urea, and urate, each within their naturally occurring physiological range.

The use of CMOS platforms in medical point-of-care applications, by integrating all steps from sample to data output, has the potential to reduce the diagnostic cost and the time from days to seconds. Here we present the ‘Multicorder’ technology, a handheld versatile multimodal platform for rapid metabolites quantification. The current platform is composed of a cartridge, a reader and a graphic user interface. The sensing core of the cartridge is the CMOS chip which integrates a 16x16 array of multi-sensor elements. Each element is composed of two optical and one chemical sensor. The platform is therefore capable of performing multi-mode measurements: namely colorimetric, chemiluminescence, pH sensing and surface plasmon resonance. In addition to the reader that is employed for addressing, data digitization and transmission, a tablet computer performs data collection, visualization, analysis and storage. In this paper, we demonstrate colorimetric, chemiluminescence and pH sensing on the same platform by on-chip quantification of different metabolites in their physiological range. The platform we have developed has the potential to lead the way to a new generation of commercial devices in the footsteps of the current commercial glucometers for quick multi-metabolite quantification for both acute and chronic medicines.

The authors have developed a wireless fluorescence imaging capsule endoscope, potentially capable of detecting early signs of disease in the human intestine which can be missed by white-light imaging (WLI) capsule endoscopy (Figure 1). Intestinal fluorescence imaging exploits variations in tissue autofluorescence between healthy and diseased areas in response to illumination, or application of fluorescent labels which preferentially bind to diseased sites. To validate the capsule’s capability to image fluorescently-labelled tissue, a small area of a sample of ex vivo porcine small intestine was sonicated with 6 nm CdZnMg fluorescent quantum dots, and the labelled area clearly differentiated from surrounding tissue by the fluorescence imaging capsule.

Colorimetric, chemiluminescence and refractive index based diagnostics are some of the most important sensing techniques in biomedical science and clinical medicine. Conventionally laboratories and medical clinics rely on bulky and dedicated equipment for each diagnostic technique independently. In this paper, we present CMOS sensor based solutions, comprising a single photon avalanche detector array and photodiode array. The CMOS platform offers low cost integration and wide range of light-based diagnostic techniques, leading to development of point-of-care devices.

Video capsule endoscopy (VCE) is now a clinically accepted diagnostic modality in which miniaturized technology, an on-board power supply and wireless telemetry stand as technological foundations for other capsule endoscopy (CE) devices. However, VCE does not provide therapeutic functionality, and research towards therapeutic CE (TCE) has been limited. In this paper, a route towards viable TCE is proposed, based on multiple CE devices including important acoustic sensing and drug delivery components. In this approach, an initial multimodal diagnostic device with high-frequency quantitative microultrasound that complements video imaging allows surface and subsurface visualization and computer-assisted diagnosis. Using focused ultrasound (US) to mark sites of pathology with exogenous fluorescent agents permits follow-up with another device to provide therapy. This is based on an US-mediated targeted drug delivery system with fluorescence imaging guidance. An additional device may then be utilized for treatment verification and monitoring, exploiting the minimally invasive nature of CE. While such a theranostic patient pathway for gastrointestinal treatment is presently incomplete, the description in this paper of previous research and work under way to realize further components for the proposed pathway suggests it is feasible and provides a framework around which to structure further work.