Driving modes and characteristics of biomedical micro-robots

Micro-robots(MRs)are miniature machines with dimensions smaller than 1 mm and have semior fully-autonomous capabilities,including sensing,decision-making,and performing operations.These MRs have garnered significant attention in the precision medicine and personalized treatment field due to their ability to navigate narrow areas of the human body with non-desirable fluid flow.Specifically,MRs are actuated by a mechanism that generates propulsive force through the interaction between MRs’actuation modules and external energy sources in a specific direction.This driving mechanism enables the precise execution of medical treatment such as targeted drug delivery and minimally invasive surgeries.Nonetheless,MRs currently encounter certain challenges in clinical practice,including reliance on external energy sources,short lifespan,and difficulties in degradation or recovery within the human body.This article aims to review the common components and characteristics of driving mechanism for MRs’actuation modules,propose possible solutions to address current clinical challenges,and ultimately,explore the desirable structural and functional composition for the future development of MRs.Through these efforts,this review hopes to provide guidance for the future development of MRs in the field of precision medicine.

All-solid-state carbon-nanotube-fiber-based finger-muscle and robotic gripper

Carbon nanotube fibers(CNTFs)have many desirable properties such as lightweight,high strength,high conductivity,and long lifetimes.Coiled CNTF is an ideal material for preparing electrochemically driven artificial muscles.While previous studies focused mainly on the actuation performance of artificial muscles made of CNTF,this study focuses on an actuator that mimics human finger movements(flexion).More specifically,the preparation of CNTF muscles were optimized by twisting with weight.Then,actuators are designed and assembled by combining all-solid-state CNTF muscles with polypropylene(PP)sheets.Moreover,a dualelectrode system,which is infiltrated by a gel electrolyte,is built into the muscle actuator.In addition,a robotic gripper is fabricated,which uses these actuators.This study can help improve the design of CNTF-based muscle-actuators and future applications in robotics.

Novel homodyne frequency-shifting interference pattern locking system

We present a novel homodyne frequency-shifting interference pattern locking system to enhance the exposure contrast of interference lithography and scanning beam interference lithography（SBIL）. The novel interference pattern locking system employs a special homodyne redundant phase measurement interferometer（HRPMI） as the sensor and an acousto-opto modulator（AOM） as the actuator. The HRPMI offers the highly accurate value as well as the direction recognition of the interference pattern drift from four quadrature interference signals. The AOM provides a very fine resolution with a high speed for phase modulation. A compact and concise system with a short optical path can be achieved with this new scheme and a small power laser head in tens of microwatts is sufficient for exposure and phase locking, which results in a relatively low-cost system compared with the heterodyne system. More importantly, the accuracy of the system is at a high level as well as having robustness to environmental fluctuation. The experiment results show that the short-time（4 s） accuracy of the system is 0.0481 rad e3σT at present. Moreover, the phase of the interference pattern can also be set arbitrarily to any value with a high accuracy in a relatively large range, which indicates that the system can also be extended to the SBIL application.

A new technique to measure the differential XAFS spectrum

A new technique has been developed for direct measurement of the differential X-ray absorption fine structure（XAFS） spectrum by the energy-modulation method. To acquire the energy-oscillating incident X-ray beam, a piezoelectric actuator is used to control the double-crystal monochromator. A logarithmic converter circuit and a lock-in amplifier are used to extract the modulated signals. The normal and differential XAFS spectra of the Mn K-edge of Li2 Mn O3 have been collected. The X-ray-absorption near-edge-structure（XANES） spectra verify that the signal-to-noise ratio has been greatly improved by the new technique, and the extended X-ray absorption fine structure（EXAFS） spectra demonstrate that this new technique can efficiently enhance the signals of the backscattering atoms.