Task space adaptation via the learning of gait controllers of magnetic soft millirobots.

Untethered small-scale soft robots have promising applications in minimally invasive surgery, targeted drug delivery, and bioengineering applications as they can directly and non-invasively access confined and hard-to-reach spaces in the human body. For such potential biomedical applications, the adaptivity of the robot control is essential to ensure the continuity of the operations, as task environment conditions show dynamic variations that can alter the robot's motion and task performance. The applicability of the conventional modeling and control methods is further limited for soft robots at the small-scale owing to their kinematics with virtually infinite degrees of freedom, inherent stochastic variability during fabrication, and changing dynamics during real-world interactions. To address the controller adaptation challenge to dynamically changing task environments, we propose using a probabilistic learning approach for a millimeter-scale magnetic walking soft robot using Bayesian optimization (BO) and Gaussian processes (GPs). Our approach provides a data-efficient learning scheme by finding the gait controller parameters while optimizing the stride length of the walking soft millirobot using a small number of physical experiments. To demonstrate the controller adaptation, we test the walking gait of the robot in task environments with different surface adhesion and roughness, and medium viscosity, which aims to represent the possible conditions for future robotic tasks inside the human body. We further utilize the transfer of the learned GP parameters among different task spaces and robots and compare their efficacy on the improvement of data-efficient controller learning.

Reconfigurable multifunctional ferrofluid droplet robots.

Magnetically actuated miniature soft robots are capable of programmable deformations for multimodal locomotion and manipulation functions, potentially enabling direct access to currently unreachable or difficult-to-access regions inside the human body for minimally invasive medical operations. However, magnetic miniature soft robots are so far mostly based on elastomers, where their limited deformability prevents them from navigating inside clustered and very constrained environments, such as squeezing through narrow crevices much smaller than the robot size. Moreover, their functionalities are currently restricted by their predesigned shapes, which is challenging to be reconfigured in situ in enclosed spaces. Here, we report a method to actuate and control ferrofluid droplets as shape-programmable magnetic miniature soft robots, which can navigate in two dimensions through narrow channels much smaller than their sizes thanks to their liquid properties. By controlling the external magnetic fields spatiotemporally, these droplet robots can also be reconfigured to exhibit multiple functionalities, including on-demand splitting and merging for delivering liquid cargos and morphing into different shapes for efficient and versatile manipulation of delicate objects. In addition, a single-droplet robot can be controlled to split into multiple subdroplets and complete cooperative tasks, such as working as a programmable fluidic-mixing device for addressable and sequential mixing of different liquids. Due to their extreme deformability, in situ reconfigurability and cooperative behavior, the proposed ferrofluid droplet robots could open up a wide range of unprecedented functionalities for lab/organ-on-a-chip, fluidics, bioengineering, and medical device applications.

Reprogrammable shape morphing of magnetic soft machines.

Shape-morphing magnetic soft machines are highly desirable for diverse applications in minimally invasive medicine, wearable devices, and soft robotics. Despite recent progress, current magnetic programming approaches are inherently coupled to sequential fabrication processes, preventing reprogrammability and high-throughput programming. Here, we report a high-throughput magnetic programming strategy based on heating magnetic soft materials above the Curie temperature of the embedded ferromagnetic particles and reorienting their magnetic domains by applying magnetic fields during cooling. We demonstrate discrete, three-dimensional, and reprogrammable magnetization with high spatial resolution (~38 µm). Using the reprogrammable magnetization capability, reconfigurable mechanical behavior of an auxetic metamaterial structure, tunable locomotion of a surface-walking soft robot, and adaptive grasping of a soft gripper are shown. Our approach further enables high-throughput magnetic programming (up to 10 samples/min) via contact transfer. Heat-assisted magnetic programming strategy described here establishes a rich design space and mass-manufacturing capability for development of multiscale and reprogrammable soft machines.

Secondary school pupils' food choices around schools in a London borough: Fast food and walls of crisps.

The objective was to observe and document food behaviours of secondary school pupils from schools in a London borough. The research design combined a number of methods which included geographic information system (GIS) mapping of food outlets around three schools, systemised observations of food purchasing in those outlets before, during and after school, and focus groups conducted with pupils of those schools to gather their views in respect to those food choices. Results are summarised under the five 'A's of Access, Availability, Affordability and Acceptability & Attitudes: Access in that there were concentrations of food outlets around the schools. The majority of pupil food purchases were from newsagents, small local shops and supermarkets of chocolate, crisps (potato chips), fizzy drinks and energy drinks. Availability of fast food and unhealthy options were a feature of the streets surrounding the schools, with 200 m the optimal distance pupils were prepared to walk from and back to school at lunchtime. Affordability was ensured by the use of a consumer mentality and pupils sought out value for money offers; group purchasing of 'two for one' type offers encouraged this trend. Pupils reported healthy items on sale in school as expensive, and also that food was often sold in smaller portion sizes than that available from external food outlets. Acceptability and Attitudes, in that school food was not seen as 'cool', queuing for school food was not acceptable but queuing for food from takeaways was not viewed negatively; for younger pupils energy drinks were 'cool'. In conclusion, pupils recognised that school food was healthier but provided several reasons for not eating in school related to the five 'A's above.

The effect of a new calcium-based agent, Pro-Argin, on the microhardness of bleached enamel surface.

BACKGROUND: This study investigated the effects of Pro-Argin application on the microhardness of bleached enamel and compared them with those of acidulated phosphate fluoride (APF) and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) applications. METHODS: Forty blocks (4 × 4 × 4 mm) were prepared from the facial surfaces of 10 sound bovine incisors. The enamel surfaces were bleached with 35% hydrogen peroxide three times at 5-day intervals. The specimens were divided into five treatment regimen groups (n = 8 each): Group 1, bleaching/no surface treatment (control); Group 2, bleaching/Pro-Argin toothpaste treatment; Group 3, bleaching/Pro-Argin treatment; Group 4, bleaching/APF treatment; and Group 5, bleaching/CPP-ACP treatment. During bleaching treatments, specimens were stored in artificial saliva. Vickers microhardness measurements were performed at baseline and after treatment in all groups. Statistical analyses were performed using the paired t-test, one-way analysis of variance, and post hoc least significant difference tests. RESULTS: After bleaching, hardness values of enamel surfaces increased significantly in the treatment groups versus the control group (p < 0.05). However, no significant difference was found among treatment groups (p > 0.05). CONCLUSIONS: Through bleaching treatment, Pro-Argin application may have a positive effect on enamel surface hardness, equivalent to that of CPP-ACP or APF.