Earthworm-Inspired Soft Skin Crawling Robot.

Earthworms are fascinating animals capable of crawling and burrowing through various terrains using peristaltic motion and the directional friction response of their epidermis. Anisotropic anchoring governed by tiny appendages on their skin called setae is known to enhance the earthworm's locomotion. A multi-material fabrication technique is employed to produce soft skins with bristles inspired by the earthworm epidermis and their setae. The effect of bristles arranged in triangular and square grids at two spatial densities on the locomotion capability of a simple soft crawling robot comprised of an extending soft actuator covered by the soft skin is investigated experimentally. The results suggest that the presence of bristles results in a rostral to caudal friction ratio of µR/µC > 1 with some variations across bristle arrangements and applied elongations. Doubling the number of bristles increases the robot's speed by a factor of 1.78 for the triangular grid while it is less pronounced for the rectangular grid with a small factor of 1.06. Additionally, it is observed that increasing the actuation stroke for the skin with the high-density triangular grid, from 15% to 30%, elevates the speed from 0.5 to 0.9 mm s-1, but further increases in stroke to 45% may compromise the durability of the actuators with less gains in speed (1 mm s-1). Finally, it is demonstrated that a crawling robot equipped with soft skin can traverse both a linear and a curved channel.

Frictional Anisotropic Locomotion and Adaptive Neural Control for a Soft Crawling Robot.

Crawling animals with bendable soft bodies use the friction anisotropy of their asymmetric body structures to traverse various substrates efficiently. Although the effect of friction anisotropy has been investigated and applied to robot locomotion, the dynamic interactions between soft body bending at different frequencies (low and high), soft asymmetric surface structures at various aspect ratios (low, medium, and high), and different substrates (rough and smooth) have not been studied comprehensively. To address this lack, we developed a simple soft robot model with a bioinspired asymmetric structure (sawtooth) facing the ground. The robot uses only a single source of pressure for its pneumatic actuation. The frequency, teeth aspect ratio, and substrate parameters and the corresponding dynamic interactions were systematically investigated and analyzed. The study findings indicate that the anterior and posterior parts of the structure deform differently during the interaction, generating different frictional forces. In addition, these parts switched their roles dynamically from push to pull and vice versa in various states, resulting in the robot's emergent locomotion. Finally, autonomous adaptive crawling behavior of the robot was demonstrated using sensor-driven neural control with a miniature laser sensor installed in the anterior part of the robot. The robot successfully adapted its actuation frequency to reduce body bending and crawl through a narrow space, such as a tunnel. The study serves as a stepping stone for developing simple soft crawling robots capable of navigating cluttered and confined spaces autonomously.

The Sounds of Softness. Designing Sound for Human-Soft Robot Interaction.

In this article, we report on research and creative practice that explores the aesthetic interplay between movement and sound for soft robotics. Our inquiry seeks to interrogate what sound designs might be aesthetically engaging and appropriate for soft robotic movement in a social human-robot interaction setting. We present the design of a soft sound-producing robot, SONO, made of pliable and expandable silicone and three sound designs made for this robot. The article comprises an articulation of the underlying design process and results from two empirical interaction experiments (N = 66, N = 60) conducted to evaluate the sound designs. The sound designs did not have statistically significant effects on people's perception of the social attributes of two different soft robots. Qualitative results, however, indicate that people's interpretations of the sound designs depend on robot type.

Enzymatic degradation of lignin-carbohydrate complexes (LCCs): model studies using a fungal glucuronoyl esterase from Cerrena unicolor.

Lignin-carbohydrate complexes (LCCs) are believed to influence the recalcitrance of lignocellulosic plant material preventing optimal utilization of biomass in e.g. forestry, feed and biofuel applications. The recently emerged carbohydrate esterase (CE) 15 family of glucuronoyl esterases (GEs) has been proposed to degrade ester LCC bonds between glucuronic acids in xylans and lignin alcohols thereby potentially improving delignification of lignocellulosic biomass when applied in conjunction with other cellulases, hemicellulases and oxidoreductases. Herein, we report the synthesis of four new GE model substrates comprising α- and É£-arylalkyl esters representative of the lignin part of naturally occurring ester LCCs as well as the cloning and purification of a novel GE from Cerrena unicolor (CuGE). Together with a known GE from Schizophyllum commune (ScGE), CuGE was biochemically characterized by means of Michaelis-Menten kinetics with respect to substrate specificity using the synthesized compounds. For both enzymes, a strong preference for 4-O-methyl glucuronoyl esters rather than unsubstituted glucuronoyl esters was observed. Moreover, we found that α-arylalkyl esters of methyl α-D-glucuronic acid are more easily cleaved by GEs than their corresponding É£-arylalkyl esters. Furthermore, our results suggest a preference of CuGE for glucuronoyl esters of bulky alcohols supporting the suggested biological action of GEs on LCCs. The synthesis of relevant GE model substrates presented here may provide a valuable tool for the screening, selection and development of industrially relevant GEs for delignification of biomass.

Modifications in Thermus thermophilus 23 S ribosomal RNA are centered in regions of RNA-RNA contact.

Ribosomal RNA from all organisms contains post-transcriptionally modified nucleotides whose function is far from clear. To gain insight into the molecular interactions of modified nucleotides, we investigated the modification status of Thermus thermophilus 5 S and 23 S ribosomal RNA by mass spectrometry and chemical derivatization/primer extension. A total of eleven modified nucleotides was found in 23 S rRNA, of which eight were singly methylated nucleotides and three were pseudouridines. These modified nucleotides were mapped into the published three-dimensional ribosome structure. Seven of the modified nucleotides located to domain IV, and four modified nucleotides located to domain V of the 23 S rRNA. All posttranscriptionally modified nucleotides map in the center of the ribosome, and none of them are in contact with ribosomal proteins. All except one of the modified nucleotides were found in secondary structure elements of the 23 S ribosomal RNA that contact either 16 S ribosomal RNA or transfer RNA, with five of these nucleotides physically involved in intermolecular RNA-RNA bridges. These findings strongly suggest that the post-transcriptional modifications play a role in modulating intermolecular RNA-RNA contacts, which is the first suggestion on a specific function of endogenous ribosomal RNA modifications.

Identifying the methyltransferases for m(5)U747 and m(5)U1939 in 23S rRNA using MALDI mass spectrometry.

There are three sites of m(5)U modification in Escherichia coli stable RNAs: one at the invariant tRNA position U54 and two in 23S rRNA at the phylogenetically conserved positions U747 and U1939. Each of these sites is modified by its own methyltransferase, and the tRNA methyltransferase, TrmA, is well-characterised. Two open reading frames, YbjF and YgcA, are approximately 30% identical to TrmA, and here we determine the functions of these candidate methyltransferases using MALDI mass spectrometry. A purified recombinant version of YgcA retains its activity and specificity, and methylates U1939 in an RNA transcript in vitro. We were unable to generate a recombinant version of YbjF that retained in vitro activity, so the function of this enzyme was defined in vivo by engineering a ybjF knockout strain. Comparison of the methylation patterns in 23S rRNAs from YbjF(+) and YbjF(-) strains showed that the latter differed only in the lack of the m(5)U747 modification. With this report, the functions of all the E.coli m(5)U RNA methyltransferases are identified, and a more appropriate designation for YbjF would be RumB (RNA uridine methyltransferases B), in line with the recent nomenclature change for YgcA (now RumA).

Detection of pseudouridine and other modifications in tRNA by cyanoethylation and MALDI mass spectrometry.

Mass spectrometry plays a central role in the characterisation of modified nucleotides, but pseudouridine is a mass-silent post-transcriptional modification and hence not detectable by direct mass spectrometric analysis. We show by the use of matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry that pseudouridines in tRNA can be specifically cyanoethylated by acrylonitrile without affecting the uridines. The tRNA was cyanoethylated and then subjected to digestion with either RNase A or RNase T1. Cyanoethylated digestion fragments were identified by mass spectrometric comparison of untreated and acrylonitrile-treated samples, where the addition of one acrylonitrile resulted in a mass increment of 53.0 Da. The exact modified nucleotide could be identified by tandem mass spectrometry on the cyanoethylated digestion fragment. The methodology was used to identify additional one 4-thiouridine and one pseudouridine in tRNA(TyrII) from Escherichia coli. Furthermore, we observed that RNase A is highly tolerant towards nucleotide modifications, only being inhibited by 2'-O-methylation, whereas RNase T1 cleavage is affected by most nucleotide modifications.