Pacific lamprey inspired climbing.

Snakes and their bio-inspired robot counterparts have demonstrated locomotion on a wide range of terrains. However, dynamic vertical climbing is one locomotion strategy that has received little attention in the existing snake robotics literature. We demonstrate a new scansorial gait and robot inspired by the locomotion of the Pacific lamprey. This new gait allows a robot to steer while climbing on flat, near-vertical surfaces. A reduced-order model is developed and used to explore the relationship between body actuation and the vertical and lateral motions of the robot. Trident, the new wall climbing lamprey-inspired robot, demonstrates dynamic climbing on a flat near vertical carpeted wall with a peak net vertical stride displacement of 4.1 cm per step. Actuating at 1.3 Hz, Trident attains a vertical climbing speed of 4.8 cm s-1(0.09 Bl s-1) at specific resistance of 8.3. Trident can also traverse laterally at 9 cm s-1(0.17 Bl s-1). Moreover, Trident is able to make 14% longer strides than the Pacific lamprey when climbing vertically. The computational and experimental results demonstrate that a lamprey-inspired climbing gait coupled with appropriate attachment is a useful climbing strategy for snake robots climbing near vertical surfaces with limited push points.

AquaClimber: a limbed swimming and climbing robot based on reduced order models.

Many legged robots have taken insight from animals to run, jump, and climb. Very few, however, have extended the flexibility of limbs to the task of swimming. In this paper, we address the study of multi-modal limbed locomotion by extending our lateral plane reduced order dynamic model of climbing to swimming. Following this, we develop a robot, AquaClimber, which utilizes the model's locomotive style, similar to human freestyle swimming, to propel itself through fluid and to climb vertical walls, as well as transition between the two. A comparison of simulation and model results indicate that the simulation can predict how hand design, arm compliance, and driving frequency affect swimming speed and behavior. Using this reduced order model, we have successfully developed the first limbed aquatic-scansorial multi-modal robot.

Legged locomotion in resistive terrains.

The utility, efficiency, and reliability of legged robots has increased dramatically in recent years. Limbed robots are now capable of locomotion across a variety of terrains, however, achieving both rapid and efficient operation when ground conditions are complex or deformable is still challenging. Resistive terrains such as streams, snow, mud, littoral regions, and tall grass are an important class or set of complex and difficult terrain which are commonly found in the desired operating environments of legged robots. This work presents a reduced-order, dynamic model designed to capture the effect of these environments on the legs of a robot while running. This model, and an experimental platform, are used to evaluate the efficacy of a pair of strategies for adapting running to the inevitable slowing that occurs in resistive terrains. Simulation and experimental results show that intelligent retraction of the foot during flight has a more beneficial effect on the maximum achievable velocity and cost of transport of the runner than a 'punting gait' for a range of fluid depths. However, this performance gap became much smaller in deep fluids suggesting that fluid depth may drive transition from a foot retraction gait to a punting gait.

Viscoelastic legs for open-loop control of gram-scale robots.

Gram-scale insects, such as cockroaches, take advantage of the mechanical properties of the musculoskeletal system to enable rapid and robust running. Engineering gram-scale robots, much like their biological counterparts, comes with inherent constraints on resources due to their small sizes. Resource-constrained robots are generally limited in their computational complexity, making controlled, high-speed locomotion a challenge, especially in unstructured environments. In this paper we show that embedding control into the leg mechanics of robots, similarly to cockroaches, results in predictable dynamics from an open-loop control strategy that can be modified through material choice. Tuning the mechanical properties of gram-scale robot legs promotes high-speed, stable running, reducing the need for active control. We utilize a torque-driven damped spring-loaded inverted pendulum model to explore the behavior and the design space of a spring-damper leg at this scale. The resulting design maps show the trade-offs in performance goals, such as speed and efficiency, with stability, as well as the sensitivity in performance to the leg properties and the control input. Finally, we demonstrate experimental results with magnetically actuated quadrupedal gram-scale robots, incorporating viscoelastic legs and demonstrating speeds up to 11.7 body lengths per second.

Impact of slope on dynamics of running and climbing.

By combining biological studies and modeling work, the dynamics of running on horizontal terrain and climbing pure vertical surfaces have been distilled down to simple reduced order models. These models have inspired distinct control and design considerations for robots operating in each terrain. However, while the extremes are understood, the intermediate regions of moderate slopes have yet to be fully explored. In this paper, we examine how cockroaches vary their behavior as slope is changed from horizontal to vertical, with special care to examine individual leg forces when possible. The results are then compared with a lateral leg spring based (LLS, horizontal running) and Full-Goldman based (FG, vertical running) models. Overall, from the experimental data, there appears to be a continuous shift in the dynamics as slope varies, which is confirmed by similar behaviors exhibited by the LLS and FG models. Finally, by examining the stability and efficiency of the models, it is shown that there are stability limits related to the amount of energy added by the front versus rear legs. This corresponds to the shift in leg usage demonstrated by the biological experiments and may have significant implications for the design and control of multi-modal robotic systems.

Evidence for multiple dynamic climbing gait families.

While numerous gait families have been defined and studied for legged systems traversing level ground (e.g. walking, running, bounding, etc), formal distinctions have yet to be developed for dynamic gaits in the vertical regime. Recognition and understanding of different gait families has clear implications to control strategy, efficiency, and stability. While several climbing robotic systems have been described as achieving 'running' behaviors on vertical surfaces, the question of whether distinct dynamic gaits exist and what differentiates these gaits has not been rigorously explored. In this paper, by applying definitions developed in the horizontal regime to simulation and experimental data, we show evidence of three distinct dynamic climbing gaits families and discuss the implications of these gaits on the development of more advanced climbing robots.

Characterization of running with compliant curved legs.

Running with compliant curved legs involves the progression of the center of pressure, the changes of both the leg's stiffness and effective rest length, and the shift of the location of the maximum stress point along the leg. These phenomena are product of the geometric and material properties of these legs, and the rolling motion produced during stance. We examine these aspects with several reduced-order dynamical models to relate the leg's design parameters (such as normalized foot radius, leg's effective stiffness, location of the maximum stress point and leg shape) to running performance (such as robustness and efficiency). By using these models, we show that running with compliant curved legs can be more efficient, robust with fast recovery behavior from perturbations than running with compliant straight legs. Moreover, the running performance can be further improved by tuning these design parameters in the context of running with rolling. The results shown in this work may serve as potential guidance for future compliant curved leg designs that may further improve the running performance.

Towards highly-tuned mobility in multiple domains with a dynamical legged platform.

As mobile robots become more commonly utilized in everyday applications, the tasks they are given will often require them to quickly traverse unprepared and varied environments. While traditional mobile platforms may falter under such conditions, animals utilize distinct locomotion modalities such as running, jumping, or climbing, to adroitly negotiate a wide variety of challenging and changing terrains. Due to limitations including available on-board power, legged robots have struggled to match the speed of these animals, even in a single mode of transport. In this paper we experimentally investigate the synergies and trade-offs in developing a dynamical legged robot capable of both running and climbing. We utilize bio-inspired 'templates' or reduced-order models of motion to identify how the dynamics change from running to climbing and seek to identify a minimal set of robotic adjustments necessary to switch locomotion modalities. This template-based design methodology is explained and the resultant robot behavior in each domain is characterized. We show that using a trotting gait, the platform demonstrates running speeds of up to 0.67 ms(-1) on level ground and climbing speeds of up to 0.43 ms(-1)on near-vertical surfaces (and up to 0.16 ms(-1) on vertical surfaces) while exhibiting dynamical behaviors comparable to that of the inspirational models.

Running up a wall: the role and challenges of dynamic climbing in enhancing multi-modal legged systems.

Animals have demonstrated the ability to move through, across and over some of the most daunting environments on earth. This versatility and adaptability stems from their capacity to alter their locomotion dynamics and employ disparate locomotion modalities to suit the terrain at hand. As with modalities such as running, flying and swimming, dynamic climbing is commonly employed by legged animals, allowing for rapid and robust locomotion on vertical and near-vertical substrates. While recent robotic platforms have proven effective at anchoring reduced-order, dynamic climbing models, its adoption as a common modality for multi-modal, legged platforms remains nascent. In this work, we explore several of the open questions related to the physical implementation of dynamic climbing, including investigation of substrate inclinations for which dynamic climbing is suited, mitigation of destabilizing out-of-plane dynamics and improvement of attachment reliability in the presence of dynamic effects. The results from these inquiries provide several mechanisms and approaches for increasing the reliability and versatility of dynamic climbing as a dynamic legged modality. With these and other developments into legged locomotion modalities, future multi-modal platforms will begin to approach the expertise of biological creatures at moving through a complex and challenging world.

Aligned electrospun nanofibers for ultra-thin layer chromatography.

The fabrication and implementation of aligned electrospun polyacrylonitrile (PAN) nanofibers as a stationary phase for ultra-thin layer chromatography (UTLC) is described. The aligned electrospun UTLC plates (AE-UTLC) were characterized to give an optimized electrospun mat consisting of high nanofiber alignment and a mat thickness of ~25 µm. The AE-UTLC devices were used to separate a mixture of ß-blockers and steroidal compounds to illustrate the properties of AE-UTLC. The AE-UTLC plates provided shorter analysis time (~2-2.5 times faster) with improved reproducibility (as high as 2 times) as well as an improvement in efficiency (up to100 times greater) relative to non-aligned electrospun-UTLC (E-UTLC) devices.

SLC1A5 mediates glutamine transport required for lung cancer cell growth and survival.

PURPOSE: We have previously identified solute-linked carrier family A1 member 5 (SLC1A5) as an overexpressed protein in a shotgun proteomic analysis of stage I non-small cell lung cancer (NSCLC) when compared with matched controls. We hypothesized that overexpression of SLC1A5 occurs to meet the metabolic demand for lung cancer cell growth and survival. EXPERIMENTAL DESIGN: To test our hypothesis, we first analyzed the protein expression of SLC1A5 in archival lung cancer tissues by immunohistochemistry and immunoblotting (N = 98) and in cell lines (N = 36). To examine SLC1A5 involvement in amino acid transportation, we conducted kinetic analysis of l-glutamine (Gln) uptake in lung cancer cell lines in the presence and absence of a pharmacologic inhibitor of SLC1A5, gamma-l-Glutamyl-p-Nitroanilide (GPNA). Finally, we examined the effect of Gln deprivation and uptake inhibition on cell growth, cell-cycle progression, and growth signaling pathways of five lung cancer cell lines. RESULTS: Our results show that (i) SLC1A5 protein is expressed in 95% of squamous cell carcinomas (SCC), 74% of adenocarcinomas (ADC), and 50% of neuroendocrine tumors; (ii) SLC1A5 is located at the cytoplasmic membrane and is significantly associated with SCC histology and male gender; (iii) 68% of Gln is transported in a Na(+)-dependent manner, 50% of which is attributed to SLC1A5 activity; and (iv) pharmacologic and genetic targeting of SLC1A5 decreased cell growth and viability in lung cancer cells, an effect mediated in part by mTOR signaling. CONCLUSIONS: These results suggest that SLC1A5 plays a key role in Gln transport controlling lung cancer cells' metabolism, growth, and survival.

Co-expression network analysis identifies Spleen Tyrosine Kinase (SYK) as a candidate oncogenic driver in a subset of small-cell lung cancer.

BACKGROUND: Oncogenic mechanisms in small-cell lung cancer remain poorly understood leaving this tumor with the worst prognosis among all lung cancers. Unlike other cancer types, sequencing genomic approaches have been of limited success in small-cell lung cancer, i.e., no mutated oncogenes with potential driver characteristics have emerged, as it is the case for activating mutations of epidermal growth factor receptor in non-small-cell lung cancer. Differential gene expression analysis has also produced SCLC signatures with limited application, since they are generally not robust across datasets. Nonetheless, additional genomic approaches are warranted, due to the increasing availability of suitable small-cell lung cancer datasets. Gene co-expression network approaches are a recent and promising avenue, since they have been successful in identifying gene modules that drive phenotypic traits in several biological systems, including other cancer types. RESULTS: We derived an SCLC-specific classifier from weighted gene co-expression network analysis (WGCNA) of a lung cancer dataset. The classifier, termed SCLC-specific hub network (SSHN), robustly separates SCLC from other lung cancer types across multiple datasets and multiple platforms, including RNA-seq and shotgun proteomics. The classifier was also conserved in SCLC cell lines. SSHN is enriched for co-expressed signaling network hubs strongly associated with the SCLC phenotype. Twenty of these hubs are actionable kinases with oncogenic potential, among which spleen tyrosine kinase (SYK) exhibits one of the highest overall statistical associations to SCLC. In patient tissue microarrays and cell lines, SCLC can be separated into SYK-positive and -negative. SYK siRNA decreases proliferation rate and increases cell death of SYK-positive SCLC cell lines, suggesting a role for SYK as an oncogenic driver in a subset of SCLC. CONCLUSIONS: SCLC treatment has thus far been limited to chemotherapy and radiation. Our WGCNA analysis identifies SYK both as a candidate biomarker to stratify SCLC patients and as a potential therapeutic target. In summary, WGCNA represents an alternative strategy to large scale sequencing for the identification of potential oncogenic drivers, based on a systems view of signaling networks. This strategy is especially useful in cancer types where no actionable mutations have emerged.

Running over unknown rough terrain with a one-legged planar robot.

The ability to traverse unknown, rough terrain is an advantage that legged locomoters have over their wheeled counterparts. However, due to the complexity of multi-legged systems, research in legged robotics has not yet been able to reproduce the agility found in the animal kingdom. In an effort to reduce the complexity of the problem, researchers have developed single-legged models to gain insight into the fundamental dynamics of legged running. Inspired by studies of animal locomotion, researchers have proposed numerous control strategies to achieve stable, one-legged running over unknown, rough terrain. One such control strategy incorporates energy variations into the system during the stance phase by changing the force-free leg length as a sinusoidal function of time. In this research, a one-legged planar robot capable of implementing this and other state-of-the-art control strategies was designed and built. Both simulated and experimental results were used to determine and compare the stability of the proposed controllers as the robot was subjected to unknown drop and raised step perturbations equal to 25% of the nominal leg length. This study illustrates the relative advantages of utilizing a minimal-sensing, active energy removal control scheme to stabilize running over rough terrain.

Electrospun glassy carbon ultra-thin layer chromatography devices.

The development and application of electrospun glassy carbon nanofibers for ultra-thin layer chromatography (UTLC) are described. The carbon nanofiber stationary phase is created through the electrospinning and pyrolysis of SU-8 2100 photoresist. This results in glassy carbon nanofibers with diameters of approximately 200-350 nm that form a mat structure with a thickness of approximately 15 microm. The chromatographic properties of UTLC devices produced from pyrolyzed SU-8 heated to temperatures of 600, 800, and 1000 degrees C are described. Raman spectroscopy and scanning electron microscopy (SEM) are used to characterize the physical and molecular structure of the nanofibers at each temperature. A set of six laser dyes was examined to demonstrate the applicability of the devices. Analyses of the retention properties of the individual dyes as well as the separation of mixtures of three dyes were performed. A mixture of three FITC-labeled essential amino acids: lysine, threonine and phenylalanine, was examined and fully resolved on the carbon UTLC devices as well. The electrospun glassy carbon UTLC plates show tunable retention, have plate number, N, values above 10,000, and show physical and chemical robustness for a range of mobile phases.

Thermal and mechanical multistate folding of ribonuclease H.

Two different classes of experimental techniques exist by which protein folding mechanisms are ascertained. The first class, of which circular dichroism is an example, probes thermally-induced folding. The second class, which includes atomic force microscopy and optical tweezers, measures mechanically-induced folding. In this article, we investigate if proteins fold/unfold via the same mechanisms both thermally and mechanically. We do so using Ribonuclease H, a protein that has been shown to fold through a three-state mechanism using both types of experimental techniques. A detailed, molecular-level description of the states involved in thermal and mechanical folding shows that mechanisms for both types are globally similar, but small difference exist in the most unfolded conformations. Comparison to previous work suggests a universal folding behavior for proteins with a core helical bundle.

Technique for ultrathin layer chromatography using an electrospun, nanofibrous stationary phase.

A technique for creating devices for ultrathin layer chromatography (UTLC) using an electrospinning method is described. The devices use a nanofibrous stationary phase with fiber diameters that are 400 nm. Separations of mixtures of laser dyes and mixtures of steroidal compounds were performed to illustrate the capabilities of these new UTLC media. The complete analyses were found to require very little development time and require less solvent than typical TLC methods. The efficiency of the separations was substantially improved compared to that determined using commercial phases. The retention properties and efficiency of the technique are discussed as are the effects of mat thickness and mobile phase composition on the chromatographic properties of the devices.