A Sea-Anemone-Inspired, Multifunctional, Bistable Gripper

The growing need for soft robots with secure, adaptive, and autonomous functioning in unforeseen environments favors designs with multiple functionalities. This has driven soft robotic grippers to be explored to integrate perceptual capability for augmented multifunctionality. In nature, sea anemones can detect and catch preys of various shapes and sizes effectively with extremely simple bodies because of the efficient coupling of sensing and actuation capability. Inspired by their body structures, we present a bistable gripper with multifunctionality that includes sensing (proprioceptive and exteroceptive) and multimodal gripping (grasping and pinching). The gripper exploits an array of tapered pins on the external surface of a dome membrane for gripping and a set of cylindrical markers on the internal surface of the membrane for optical sensing. The membrane is bistable and can settle in either of two equilibrium states "natural" and "retracted." Gripping functionality is achieved by the centripetal enveloping movement of the pins, along with the passive snap-through process of the membrane. By analyzing the distribution of markers within the view of an embedded camera, sophisticated sensing functionality can be achieved. We first characterized each function separately and then implemented an object handling system, combining the sensing and gripping functionality, to demonstrate the potential for more advanced robotic applications. This work delivers a compact universal gripper design with an efficient and elegant integration of multifunctionality.

Facile Photolithographic Fabrication of Zwitterionic Polymer Microneedles with Protein Aggregation Inhibition for Transdermal Drug Delivery

Microneedle technology has received considerable attention in transdermal drug delivery system research owing to its minimally invasive and convenient self-administration with enhanced transdermal transport. The pre-drug loading microneedle method has been developed for several protein and chemical medicines. However, the protein activity and efficacy are severely affected owing to protein aggregation. Herein, we aim to develop non-degradable hydrogel photocross-linkable microneedles for suppressing protein aggregation. Four-point star-shaped microneedles are fabricated via a photolithography process, and sulfobetaine (SPB) monomer is combined with dextran-glycidyl methacrylate/acrylic acid to form the hydrogel network. Incorporating zwitterionic poly-sulfobetaine (poly-SPB) in the microneedles enables the protection of proteins from denaturation even under external stress, releases the proteins in their native state (without activity loss), and exhibits sufficient mechanical strength to penetrate porcine skin. The microneedles exhibit a high drug loading capacity along with an efficient drug release rate. The rhodamine B drug loading and release model shows that the microneedles can load 8 μg of drugs on one microneedle patch of 41 needles and release nearly 80% of its load within 1 h. We anticipate that this pre-drug loading platform and the advanced features of the microneedles can provide an effective option for administering therapeutic drugs.

Anguilliform Swimming Performance of an Eel-Inspired Soft Robot

In this article, we propose a soft eel robot design using soft pneumatic actuators that mimic eel muscles. Four pairs of soft actuators are used to construct the eel robot body. Pulse signals with suitable shifting phases are utilized to control delivery of compressed air to the actuators in sequence to create a sinusoidal wave from head to tail of the robot body. A model of hydrodynamic forces acting on an anguilliform swimmer when moving in fluid was built to estimate the thrust force generated by the robot at different tail beat frequencies. Experimental data revealed that the generated thrust force was positively correlated with the beat frequency. Measured data showed that swimming efficiency depended on both generated thrust force and body posture in situ. At the beat frequency of 1.25 Hz, and air pressure at three segments from head to tail of 65, 50, and 30 kPa, respectively, the eel robot body showed the best cost of transport (COT) of 19.21 with velocity of 10.5 cm/s (or 0.198 body length per second [BL/s]), compared to the other's values of operation frequency and air pressure. We also found that control shifting phase strongly affects the swimming speed and COT. The robot body reached the highest velocity at around 19 cm/s (0.36 BL/s) with the COT of 10.72. Obtained result in this research would contribute to development of soft elongated swimming robot and enhance the knowledge on swimming performance of both robot and natural eels.

Mechanics and Morphological Compensation Strategy for Trimmed Soft Whisker Sensor

Recent studies have been inspired by natural whiskers for a proposal of tactile sensing system to augment the sensory ability of autonomous robots. In this study, we propose a novel artificial soft whisker sensor that is not only flexible but also adapts and compensates for being trimmed or broken during operation. In this morphological compensation designed from an analytical model of the whisker, our sensing device actively adjusts its morphology to regain sensitivity close to that of its original form (before being broken). To serve this purpose, the body of the whisker comprises a silicon-rubber truncated cone with an air chamber inside as the medulla layer, which is inflated to achieve rigidity. A small strain gauge is attached to the outer wall of the chamber for recording strain variation upon contact of the whisker. The chamber wall is reinforced by two inextensible nylon fibers wound around it to ensure that morphology change occurs only in the measuring direction of the strain gauge by compressing or releasing pressurized air contained in the chamber. We investigated an analytical model for the regulation of whisker sensitivity by changing the chamber morphology. Experimental results showed good agreement with the numerical results of performance by an intact whisker in normal mode, as well as in compensation mode. Finally, adaptive functionality was tested in two separate scenarios for thorough evaluation: (1) A short whisker (65 mm) compensating for a longer one (70 mm), combined with a special case (self-compensation), and (2) vice versa. Preliminary results showed good feasibility of the idea and efficiency of the analytical model in the compensation process, in which the compensator in the typical scenario performed with 20.385% average compensation error. Implementation of the concept in the present study fulfills the concept of morphological computation in soft robotics and paves the way toward accomplishment of an active sensing system that overcomes a critical event (broken whisker) based on optimized morphological compensation.

Mechanics of wet adhesion in soft interaction with patterned morphology

Locking surfaces with a wet interface can enhance interactions between a grasped object and a soft pad. This paper presents a mechanical approach to understanding the role of morphological design in achieving wet adhesion for secure grasping by a soft pad. Two conditions were compared in modeling wet interfaces between an object and a soft pad: a pad with a flat surface, and a pad with a micropatterned surface. The latter was designed and analyzed based on the wet attachment between the surface of a tree-frog's toes and its substrate. In this model, we proposed a method to estimate the contact force in both normal and tangential directions between a soft pad with a micropattern surface and a rigid flat surface substrate. A square mold containing 3600 85 μm × 85 μm cells interspaced by grooves 15 μm wide and 15 μm deep was fabricated, using e-beam technology, as the micropattern pad. The generated normal and tangential contact forces of the pad with a micropattern surface, and a pad with a flat surface were measured in both normal and tangential directions under wet conditions. Experimental results showed good agreement with theoretical results, indicating that the micropattern significantly enhanced the contact force of the pad by approximately two-fold for the normal and 1.2- to 1.4-fold for the tangential force. This theoretical approach can be potentially utilized to investigate the association of soft pad morphology with wet adhesion, and enhance efficient grasping by soft robotic hands in wet and high-moisture environments.

Multimodal flexible sensor for healthcare systems

This paper describes potential applications of our previously developed fabric sensor into wearable healthcare or nursing systems based on its sensing modalities. This sensor is knitted from tension-sensitive electro-conductive yarns; whose structure has an elastic core, wound around by two separated tension-sensitive electro-conductive threads. This makes the sensor inherently flexible and stretchable, allowing it to conform to any complicated surface. We have equipped the sensor with three modalities, including proximity that allows the sensor to estimate a distance from the sensor to human hand and activates a light touch sensing, which could initiate comfortable and friendly interfaces in order to reduce burden of patients/disable people during interactions with healthcare devices; tactile perception that can measures contact force or applied load, especially realize slippage acting on the sensor surface, which is promising to be embedded into wearable devices or smart carpets; and tensile that can quantify a volume's contraction/expansion, which can be employed to monitoring muscles activity and so on.

The efficacy of a Salmonella typhi Vi conjugate vaccine in two-to-five-year-old children

BACKGROUND

Typhoid fever is common in developing countries. The licensed typhoid vaccines confer only about 70 percent immunity, do not protect young children, and are not used for routine vaccination. A newly devised conjugate of the capsular polysaccharide of Salmonella typhi, Vi, bound to nontoxic recombinant Pseudomonas aeruginosa exotoxin A (rEPA), has enhanced immunogenicity in adults and in children 5 to 14 years old and has elicited a booster response in children 2 to 4 years old.

METHODS

In a double-blind, randomized trial, we evaluated the safety, immunogenicity, and efficacy of the Vi-rEPA vaccine in children two to five years old in 16 communes in Dong Thap Province, Vietnam. Each of the 11,091 children received two injections six weeks apart of either Vi-rEPA or a saline placebo. Cases of typhoid, diagnosed by the isolation of S. typhi from blood cultures after 3 or more days of fever (a temperature of 37.5 degrees C or higher), were identified by active surveillance over a period of 27 months. We estimated efficacy by comparing the attack rate of typhoid in the vaccine group with that in the placebo group.

RESULTS

S. typhi was isolated from 4 of the 5525 children who were fully vaccinated with Vi-rEPA and from 47 of the 5566 children who received both injections of placebo (efficacy, 91.5 percent; 95 percent confidence interval, 77.1 to 96.6; P<0.001). Among the 771 children who received only one injection, there was 1 case of typhoid in the vaccine group and 8 cases in the placebo group. Cases were distributed evenly among all age groups and throughout the study period. No serious adverse reactions were observed. In all 36 children studied four weeks after the second injection of the vaccine, levels of serum IgG Vi antibodies had increased by a factor of 10 or more.

CONCLUSIONS

The Vi-rEPA conjugate typhoid vaccine is safe and immunogenic and has more than 90 percent efficacy in children two to five years old. The antibody responses and the efficacy suggest that this vaccine should be at least as protective in persons who are more than five years old.

Typhoid fever and genetic polymorphisms at the natural resistance-associated macrophage protein 1

Control of Salmonella enterica serovar Typhimurium (S. typhimurium) infection in the mouse model of typhoid fever is critically dependent on the natural resistance-associated macrophage protein 1 (Nramp1). In this study, we examined the role of genetic polymorphisms in the human homologue, NRAMP1, in resistance to typhoid fever in southern Vietnam. Patients with blood-culture-confirmed typhoid fever and healthy control subjects were genotyped for 6 polymorphic markers within and near NRAMP1 on chromosome 2q35. Four single base-pair polymorphisms (274 C/T, 469+14 G/C, 1465-85 G/A, and D543N), a (GT)(n) repeat in the promoter region of NRAMP1 and D2S1471, and a microsatellite marker approximately 130-kb downstream of NRAMP1 were examined. The allelic and genotypic frequencies for each polymorphism were compared in case patients and control subjects. No allelic association was identified between the NRAMP1 alleles and typhoid fever susceptibility. In addition, neither homozygotes nor heterozygotes for any NRAMP1 variants were at increased risk of typhoid fever.

Serology of typhoid fever in an area of endemicity and its relevance to diagnosis

Currently, the laboratory diagnosis of typhoid fever is dependent upon either the isolation of Salmonella enterica subsp. enterica serotype Typhi from a clinical sample or the detection of raised titers of agglutinating serum antibodies against the lipopolysaccharide (LPS) (O) or flagellum (H) antigens of serotype Typhi (the Widal test). In this study, the serum antibody responses to the LPS and flagellum antigens of serotype Typhi were investigated with individuals from a region of Vietnam in which typhoid is endemic, and their usefulness for the diagnosis of typhoid fever was evaluated. The antibody responses to both antigens were highly variable among individuals infected with serotype Typhi, and elevated antibody titers were also detected in a high proportion of serum samples from healthy subjects from the community. In-house enzyme-linked immunosorbent assays (ELISAs) for the detection of specific classes of anti-LPS and antiflagellum antibodies were compared with other serologically based tests for the diagnosis of typhoid fever (Widal TO and TH, anti-serotype Typhi immunoglobulin M [IgM] dipstick, and IDeaL TUBEX). At a specificity of > or =0.93, the sensitivities of the different tests were 0.75, 0.55, and 0.52 for the anti-LPS IgM, IgG, and IgA ELISAs, respectively; 0.28 for the antiflagellum IgG ELISA; 0.47 and 0.32 for the Widal TO and TH tests, respectively; and 0.77 for the anti-serotype Typhi IgM dipstick assay. The specificity of the IDeaL TUBEX was below 0.90 (sensitivity, 0.87; specificity, 0.76). The serological assays based on the detection of IgM antibodies against either serotype Typhi LPS (ELISA) or whole bacteria (dipstick) had a significantly higher sensitivity than the Widal TO test when used with a single acute-phase serum sample (P < or = 0.007). These tests could be of use for the diagnosis of typhoid fever in patients who have clinical typhoid fever but are culture negative or in regions where bacterial culturing facilities are not available.

Genes of the class II and class III major histocompatibility complex are associated with typhoid fever in Vietnam

The influence of genes of the major histocompatibility complex (MHC) class II and class III loci on typhoid fever susceptibility was investigated. Individuals with blood culture-confirmed typhoid fever and control subjects from 2 distinct geographic locations in southern Vietnam were genotyped for HLA-DRB1 and HLA-DQB1 alleles, the gene that encodes tumor necrosis factor (TNF)-alpha (TNFA [-238] and TNFA [-308]), the gene that encodes lymphotoxin-alpha, and alleles of the TNF-alpha microsatellite. HLA-DRB1*0301/6/8, HLA-DQB1*0201-3, and TNFA*2 (-308) were associated with susceptibility to typhoid fever, whereas HLA-DRB1*04, HLA-DQB1*0401/2, and TNFA*1 (-308) were associated with disease resistance. The frequency of all possible haplotypes of the 3 individually associated loci were estimated and were found to be significantly different in typhoid case patients and control subjects (chi2=55.56, 32 df; P=.006). Haplotypes that were either protective (TNFA*1 [-308].DRB1*04) or predisposed individuals to typhoid fever (TNFA*2 [-308].DRB1*0301) were determined. This report identifies a genetic association in humans between typhoid fever and MHC class II and III genes.

Epidemic typhoid in vietnam: molecular typing of multiple-antibiotic-resistant Salmonella enterica serotype typhi from four outbreaks

Multidrug-resistant Salmonella enterica serotype Typhi isolates from four outbreaks of typhoid fever in southern Vietnam between 1993 and 1997 were compared. Pulsed-field gel electrophoresis, bacteriophage and plasmid typing, and antibiotic susceptibilities showed that independent outbreaks of multidrug-resistant typhoid fever in southern Vietnam are caused by single bacterial strains. However, different outbreaks do not derive from the clonal expansion of a single multidrug-resistant serotype Typhi strain.

Safety and immunogenicity of Vi conjugate vaccines for typhoid fever in adults, teenagers, and 2- to 4-year-old children in Vietnam

The capsular polysaccharide of Salmonella typhi, Vi, is an essential virulence factor and a protective vaccine for people older than 5 years. The safety and immunogenicity of two investigational Vi conjugate vaccines were evaluated in adults, 5- to 14-year-old children, and 2- to 4-year-old children in Vietnam. The conjugates were prepared with Pseudomonas aeruginosa recombinant exoprotein A (rEPA) as the carrier, using either N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP; Vi-rEPA(1)) or adipic acid dihydrazide (ADH; Vi-rEPA(2)) as linkers. None of the recipients experienced a temperature of >38.5 degrees C or significant local reactions. One injection of Vi-rEPA(2) into adults elicited a geometric mean (GM) increase in anti-Vi immunoglobulin G (IgG) from 9.62 enzyme-linked immunosorbent assay units/ml (EU) to 465 EU at 6 weeks; this level fell to 119 EU after 26 weeks. In the 5- to 14-year-old children, anti-Vi IgG levels at 6 weeks elicited by Vi-rEPA(2), Vi-rEPA(1), and Vi were 169, 22.8, and 18.9 EU, respectively (P = 0.0001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)). At 26 weeks, the anti-Vi IgG levels for recipients of Vi-rEPA(2), Vi-rEPA(1), and Vi were 30.0, 10.8, and 13.4 EU, respectively (P < 0.001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)); all were higher than the preinjection levels (P = 0. 0001). Vi-rEPA(2) also elicited the highest anti-Vi IgM and IgA levels of the three vaccines. In the 2- to 4-year-old children at 6 weeks following the first injection, Vi-rEPA(2) elicited an anti-Vi IgG level of 69.9 EU compared to 28.9 EU for Vi-rEPA(1) (P = 0.0001). Reinjection increased Vi antibody levels from 69.9 to 95.4 EU for Vi-rEPA(2) and from 28.9 to 83.0 EU for Vi-rEPA(1). At 26 weeks, anti-Vi IgG levels remained higher than those at preinjection (30.6 versus 0.18 for Vi-rEPA(2) and 12.8 versus 0.33 for Vi-rEPA(1); P = 0.0001 for both). Vi vaccine is recommended for individuals of 5 years of age or older. In the present study, the GM level of anti-Vi IgG elicited by two injections of Vi-rEPA(2) in the 2- to 4-year-old children was higher than that elicited by Vi in the 5- to 14-year-old children (30.6 versus 13.4; P = 0.0001). The safety and immunogenicity of the Vi-rEPA(2) conjugate warrant further investigation.

Molecular typing of multiple-antibiotic-resistant Salmonella enterica serovar Typhi from Vietnam: application to acute and relapse cases of typhoid fever

The rate of multiple-antibiotic resistance is increasing among Salmonella enterica serovar Typhi strains in Southeast Asia. Pulsed-field gel electrophoresis (PFGE) and other typing methods were used to analyze drug-resistant and -susceptible organisms isolated from patients with typhoid fever in several districts in southern Vietnam. Multiple PFGE and phage typing patterns were detected, although individual patients were infected with strains of a single type. The PFGE patterns were stable when the S. enterica serovar Typhi strains were passaged many times in vitro on laboratory medium. Paired S. enterica serovar Typhi isolates recovered from the blood and bone marrow of individual patients exhibited similar PFGE patterns. Typing of S. enterica serovar Typhi isolates from patients with relapses of typhoid indicated that the majority of relapses were caused by the same S. enterica serovar Typhi strain that was isolated during the initial infection. However, some individuals were infected with distinct and presumably newly acquired S. enterica serovar Typhi isolates.

Quantitation of bacteria in blood of typhoid fever patients and relationship between counts and clinical features, transmissibility, and antibiotic resistance

Salmonella typhi was isolated from 369 and Salmonella paratyphi A was isolated from 6 of 515 Vietnamese patients with suspected enteric fever. Compared with conventional broth culture of blood, direct plating of the buffy coat had a diagnostic sensitivity of 99.5% (95% confidence interval [CI], 97.1 to 100%). Blood bacterial counts were estimated by the pour plate method. The median S. typhi count in blood was 1 CFU/ml (range, <0.3 to 387 CFU/ml), of which a mean of 63% (95% CI, 58 to 67%) were intracellular. The mean number of bacteria per infected leukocyte was 1.3 (interquartile range [IQR], 0.7 to 2.4) CFU/cell (n = 81). Children (< 15 years old; n = 115) had higher median blood bacterial counts than adults (n = 262): 1.5 (range, <0.3 to 387) versus 0.6 (range, <0.3 to 17.7) CFU/ml (P = 0.008), and patients who excreted S. typhi in feces had higher bacteremias than those who did not: a median of 3 (range, <0.3 to 32) versus 1 (range, <0.3 to 68) CFU/ml (P = 0.02). Blood bacterial counts declined with increasing duration of illness (P = 0.002) and were higher in infections caused by multidrug-resistant S. typhi (1.3 [range, <0.3 to 387] CFU/ml; n = 313) than in infections caused by antibiotic-sensitive S. typhi (0.5 [range, <0.3 to 32] CFU/ml; n = 62) (P = 0.006). In a multivariate analysis this proved to be an independent association, suggesting a relationship between antibiotic resistance and virulence in S. typhi.