Magnetic torque-driven living microrobots for enhanced tumor infiltration

Bacterial microrobots combining self-propulsion and magnetic guidance are increasingly recognized as promising drug delivery vehicles for targeted cancer therapy. Thus far, control strategies have either relied on poorly scalable magnetic field gradients or employed directing magnetic fields with propulsive forces limited by the bacterial motor. Here, we present a magnetic torque-driven actuation scheme based on rotating magnetic fields to wirelessly control Magnetospirillum magneticum AMB-1 bearing versatile liposomal cargo. We observed a 4-fold increase in conjugate translocation across a model of the vascular endothelium and found that the primary mechanism driving this increased transport is torque-driven surface exploration at the cell interface. Using spheroids as a 3D tumor model, fluorescently labeled bacteria colonized their core regions with up to 21-fold higher signal in samples exposed to rotating magnetic fields. In addition to enhanced transport, we demonstrated the suitability of this magnetic stimulus for simultaneous actuation and inductive detection of AMB-1. Finally, we demonstrated that RMF significantly enhances AMB-1 tumor accumulation in vivo following systemic intravenous administration in mice. Our findings suggest that scalable magnetic torque-driven control strategies can be leveraged advantageously with biohybrid microrobots.

A dynamically reprogrammable metasurface with self-evolving shape morphing

Dynamic shape-morphing soft materials systems are ubiquitous in living organisms; they are also of rapidly increasing relevance to emerging technologies in soft machines1–4, flexible electronics5–7, and smart medicines8,9. Soft matter equipped with responsive components can switch between designed shapes or structures, but cannot support the types of dynamic morphing capabilities needed to reproduce natural, continuous processes of interest for many applications10–27. Challenges lie in the development of schemes to reprogram target shapes post fabrication, especially when complexities associated with the operating physics and disturbances from the environment can prohibit the use of deterministic theoretical models to guide inverse design and control strategies3,28–32. Here, we present a mechanical metasurface constructed from a matrix of filamentary metal traces, driven by reprogrammable, distributed Lorentz forces that follow from passage of electrical currents in the presence of a static magnetic field. The resulting system demonstrates complex, dynamic morphing capabilities with response times within 0.1 s. Implementing an in-situ stereo-imaging feedback strategy with a digitally controlled actuation scheme guided by an optimization algorithm, yields surfaces that can self-evolve into a wide range of 3-dimensional (3D) target shapes with high precision, including an ability to morph against extrinsic or intrinsic perturbations. These concepts support a data-driven approach to the design of dynamic, soft matter, with many unique characteristics.

A Time Division Multiplexing Inspired Lightweight Soft Exoskeleton for Hip and Ankle Joint Assistance

Exoskeleton robots are frequently applied to augment or assist the user’s natural motion. Generally, each assisted joint corresponds to at least one specific motor to ensure the independence of movement between joints. This means that as there are more joints to be assisted, more motors are required, resulting in increasing robot weight, decreasing motor utilization, and weakening exoskeleton robot assistance efficiency. To solve this problem, the design and control of a lightweight soft exoskeleton that assists hip-plantar flexion of both legs in different phases during a gait cycle with only one motor is presented in this paper. Inspired by time-division multiplexing and the symmetry of walking motion, an actuation scheme that uses different time-periods of the same motor to transfer different forces to different joints is formulated. An automatic winding device is designed to dynamically change the loading path of the assistive force at different phases of the gait cycle. The system is designed to assist hip flexion and plantar flexion of both legs with only one motor, since there is no overlap between the hip flexion movement and the toe-offs movement of the separate legs during walking. The weight of the whole system is only 2.24 kg. PD iterative control is accomplished by an algorithm that utilizes IMUs attached on the thigh recognizing the maximum hip extension angle to characterize toe-offs indirectly, and two load cells to monitor the cable tension. In the study of six subjects, muscle fatigue of the rectus femoris, vastus lateralis, gastrocnemius and soleus decreased by an average of 14.69%, 6.66%, 17.71%, and 8.15%, respectively, compared to scenarios without an exoskeleton.

Bipedal Humanoid Hardware Design: a Technology Review

Purpose of Review As new technological advancements are made, humanoid robots that utilise them are being designed and manufactured. For optimal design choices, a broad overview with insight on the advantages and disadvantages of available technologies is necessary. This article intends to provide an analysis on the established approaches and contrast them with emerging ones. Recent Findings A clear shift in the recent design features of humanoid robots is developing, which is supported by literature. As humanoid robots are meant to leave laboratories and traverse the world, compliance and more efficient locomotion are necessary. The limitations of highly rigid actuation are being tackled by different research groups in unique ways. Some focus on modifying the kinematic structure, while others change the actuation scheme. With new manufacturing capabilities, previously impossible designs are becoming feasible. Summary A comprehensive review on the technologies crucial for bipedal humanoid robots was performed. Different mechanical concepts have been discussed, along with the advancements in actuation, sensing, and manufacturing. The paper is supplemented with a list of the recently developed platforms along with a selection of their specifications.

User Expectations and Mental Models for Communicating Emotions through Compressive & Warm Affective Garment Actuation

Wearable haptic garments for communicating emotions have great potential in various applications, including supporting social interactions, improving immersive experiences in entertainment, or simply as a research tool. Shape-memory alloys (SMAs) are an emerging and interesting actuation scheme for affective haptic garments since they provide coupled warmth and compressive sensations in a single actuation---potentially acting as a proxy for human touch. However, SMAs are underutilized in current research and there are many unknowns regarding their design/use. The goal of this work is to map the design space for SMA-based garment-mediated emotional communication through warm, compressive actuation (termed 'warm touch'). Two online surveys were deployed to gather user expectations in using varying 'warm touch' parameters (body location, intensity, pattern) to communicate 7 distinct emotions. Further, we also investigated mental models used by participants during the haptic strategy selection process. The findings show 5 major categories of mental models, including representation of body sensations, replication of typical social touch strategies, metaphorical representation of emotions, symbolic representation of physical actions, and mimicry of objects or tasks; the frequency of use of each of these mental frameworks in relation to the selected 'warm touch' parameters in the communication of emotions are presented. These gathered insights can inform more intuitive and consistent haptic garment design approaches for emotional communication.

Development and on orbit test of Taiji-1 inertial reference

Taiji-1 is the first step of China’s efforts on the detection of gravitational waves in space. It is a one-year quick mission, which aims to verify the key technologies on orbit. The detection of gravitational waves at mHz frequency band needs to exceptionally focus on small spatial deviations between two inertial references several million kilometers apart. The inertial reference on Taiji-1 spacecraft (S/C) has been developed based on a capacitive readout and actuation scheme to meet the requirements of accelerometer. In this paper, the development condition, ground tests and on-orbit performance of this inertial reference are described.

Position Control with ADRC for a Hydrostatic Double-Cylinder Actuator

A compact and flexible hydraulic double-cylinder actuation scheme is proposed for use in applications, especially where power density is extremely demanding. In view of flexible amounting requirements, long and thin hoses were utilized to connect two cylinders. Affecting the actuation preciseness, volume variation of the hoses caused by pressurized oil and bubbles was the main problem the system encountered. In this study, an active disturbance rejection control (ADRC) strategy was adopted for the improvement of displacement control performance under uncertain external load. After the experimental verification of the necessity of a hose model for the system, a centralized-parameter hose model was constructed where the coefficients are determined on the basis of the experimental data. Additionally, the system and the controller proposed were mathematically modeled. Simulation results shows that the system using ADRC exhibited higher displacement accuracy and better dynamic performance than that using PID (Proportion-Integral-Derivative) or fuzzy PID. ADRC has a stronger disturbance rejection ability. ADRC is an effective solution to nonlinear control of systems with uncertain parameters or various loads.

An efficient leg with series–parallel and biarticular compliant actuation: design optimization, modeling, and control of the eLeg

We present the development, modeling, and control of a three-degree-of-freedom compliantly actuated leg called the eLeg, which employs both series- and parallel-elastic actuation as well as a bio-inspired biarticular tendon. The leg can be reconfigured to use three distinct actuation configurations, to directly compare with a state-of-the-art series-elastic actuation scheme. Critical actuation design parameters are derived through optimization. A rigorous modeling approach is presented using the concept of power flows, which are also used to demonstrate the ability to transfer mechanical power between ankle and knee joints using the biarticular tendon. The design principles and control strategies were verified both in simulation and experiment. Notably, the experimental data demonstrate significant improvements of 65–75% in electrical energy consumption compared with a state-of-the-art series-elastic actuator configuration.