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Fine dust measurement methods, such as weight change, beta ray measurement, light scattering, and resonance change, have been studied and used, but there is still room for improvement in terms of cost, system volume, and accuracy. In this study, we aimed to develop a low-cost, micro-scale, and highly accurate dust sensor using semiconductor processes. The sensor consists of a piezoelectric membrane with a diameter of 800 µm and a thickness of 2.8 µm. The resonance frequency and mode shape were measured and monitored using a Laser-Doppler-Vibrometer (LDV), and the resonance frequency shift was calculated based on the same mode shape. Vibration modes from (0,1) to (3,1) were observed within a 0–200 kHz frequency bandwidth. Spherical glass beads were used to measure resonance frequency shift for additional mass ranging from 0.863 to 4.52 µg. The first resonance mode (0,1) exhibited a clear proportional relationship between the resonance frequency shift and additional mass, while other modes exhibited non-proportional trends. Intriguingly, notable discrepancies in the resonance frequency shift emerged based on the spatial placement of the glass beads, even when the mass was the same. Additionally, we presented an approximate theoretical curve to portray the resonance frequency shift, which we subsequently validated against our measurement findings. This study presents a new attempt on the characterization method of piezoelectric mass sensors and provides a relatively simple and accurate analysis of the results.

Dopamine (DA) homeostasis influences emotions, neural circuit development, cognition, and the reward system. Dysfunctions in DA regulation can lead to neurological disorders, including depression, developmental disorders, and addiction. DA homeostasis disruption is a primary cause of Parkinson’s Disease (PD). Therefore, understanding the relationship between DA homeostasis and PD progression may clarify the mechanisms for pharmacologically treating PD. This study developed a novel in vitroDA homeostasis platform which consists of three main parts: (1) a microfluidic device for culturing DAergic neurons, (2) an optical detection system for reading DA levels, and (3) an automatic closed-loop control system that establishes when and how much medication to infuse; this uses a microfluidic device that can cultivate DAergic neurons, perfuse solutions, perform in vitroPD modeling, and continuously monitor DA concentrations. The automatically controlled closed-loop control system simultaneously monitors pharmacological PD treatment to support long-term monitoring of DA homeostasis. SH-SY5Y neuroblastoma cells were chosen as DAergic neurons. They were cultivated in the microfluidic device, and real-time cellular DA level measurements successfully achieved long-term monitoring and modulation of DA homeostasis. When applied in combination with multiday cell culture, this advanced system can be used for drug screening and fundamental biological studies.

Magnetic field mapping is tedious; a magnetometer probe collects magnetic field data in a point-by-point manner within a two-dimensional (2-D) or three-dimensional (3-D) space. Magnetometer arrays accelerate this process by replacing point-by-point mapping with plane-by-plane mapping. When mapping a large space, a motorized stage is additionally required; the limitations include power inefficiencies, large footprints, cost, and the absence of real-time data acquisition. Here, we introduce MagMaps, a modular Lego-like approach to Magnetic field mapping that overcomes the limitations described above. MagMaps includes a set of physically identical modules termed “MagBricks” that can be stacked in all three axes (similar to Lego bricks); this covers the region of interest and eliminates the need for a motorized stage. Each MagBrick is an independent enslaved module with a unique address, having a microcontroller that continuously acquires magnetic field data from a magnetometer array. An additional brick termed the “MasterBrick” serves as a bridge between the computer and the MagBricks. The MasterBrick collects magnetic field data from uniquely addressed MagBricks and communicates them to a computer, where they are sorted and displayed in real time. This modular Lego-like approach and the use of only off-the-shelf electronic components allow MagMaps to offer real-time MagMaps that is portable, power-efficient, and economical for various 2-D or 3-D spaces.

This brief presents a novel tracking control algorithm for a micro-robot based on dynamics and positional measurements. The algorithm improves the tracking performance and response time. We designed a two-degree-of-freedom (TDOF) control, which is widely utilized in industrial servo systems, for a micro-robot. Our TDOF control prevents undesirable effects, such as model uncertainty. The dynamic characteristics of a micro-robot were analyzed using the frequency response function (FRF), and a dynamic model specific for micro-robot motion was derived. This brief also addresses the dual-rate problem of micro-robot control systems by designing a dual-rate state observer (DSO) that provides positional information for the micro-robot when no camera updates are available. Thus, the TDOF controller provides feedback control at higher sampling frequencies. The performance of the controller was experimentally verified.

This review discusses the potential of degradable metallic micromotors for a variety of biomedical and environmental applications.The design principles, fabrication techniques and degradation mechanisms of degradable metallic micromotors are reviewed in detail.Challenges and future directions for the development of degradable metallic micromotors for real-life applications are presented.

Cell therapy refers to a treatment that involves the delivery of cells or cellular material by means of injection, grafting, or implantation in order to replace damaged tissue and restore its function, or to aid the body in fighting disease. However, limitations include poor targeting delivery and low therapeutic efficacy due to low cell survival. Hence, novel approaches are required to increase cell delivery efficiency and enhance therapeutic efficacy viaselective cell differentiation at target areas. Here, we present a stamping magnetoelectric microscale biorobot (SMMB) consisting of neuron-like cell spheroids loaded with magnetoelectric nanoparticles. The SMMB enables not only effective targeted delivery of cells to multiple target areas (viaminimally invasive stamping employing magnetic actuation) but also facilitates selective neuronal differentiation viamagnetoelectric (ME) stimulation. This ensures rapid colonization and enhances efficacy. SMMBs were fabricated using SH-SY5Y cells. Magnetoelectric nanoparticles for ME stimulation responded to an alternating magnetic field that ensured targeted cell differentiation. Multi-target cell therapy facilitated the targeted delivery and selective differentiation of SH-SY5Y cells to multiple regions using a single SMMB with rotating and alternating magnetic fields for delivery and ME stimulation. This promising tool may overcome the limitations of existing cell therapy for neurodegenerative diseases.

The energy harvesting by utilizing the piezoelectric effect for the conversion of oscillatory mechanical energy to useful electrical energy has been promising for self-powered devices. The output power can be controlled by designing the size and shape of the constituents of the harvester. This study demonstrates the effect of Ti plate (elastic layer) thickness on the resonant frequency, neutral axis position, vibration amplitude and energy harvesting performance of the cantilever structured piezoelectric energy harvester (PEH). Here, the each harvester had the same dimensions of piezoelectric layer and the same proof mass position at the end of the cantilever while it had the different elastic layer thicknesses (70–300 μm). The analysis revealed that the output power showed the opposite trend in vibration amplitude with varying the elastic layer thickness. Among all of the PEHs, the configuration with the largest elastic layer thickness (300 μm) exhibited a maximum output power of 48 μW at 76 Hz under 0.2 g acceleration, despite of the smallest vibration amplitude and the highest resonant frequency. The outcomes suggest that the thickness ratio of the piezoelectric and elastic layers should be optimized to realize the best harvesting performance.

Here, we develop a flexible microrobot enhancing the steerability of a conventional guidewire. To improve steerability, a microrobot is attached to the tip of the guidewire and guided using an external magnetic field generated by an electromagnetic coil system. The flexible microrobot is fabricated via replica-molding and features a body made of polydimethylsiloxane (PDMS) and a single permanent magnet. As the robot is made of a deformable material, it can be steered using a low-intensity external magnetic field; the robot can potentially be guided into the coronary artery. To study steering performance, we employed mathematical modeling and a finite element model (FEM), and performed experiments under various magnetic fields. We found that a mathematical model using the Euler–Bernoulli beam could not precisely calculate the deformation angles. The FEM more accurately estimated those angles. The deformation angle can be controlled from 0 to 80° at a magnetic field intensity of 15 mT. The trackability at angles of 45 and 80° of the guidewire-based microrobot was confirmed in vitro using a two-dimensional blood vessel phantom.

In this study, we present a piezoelectric artificial basilar membrane (ABM) composed of a 10-channel aluminum nitride beam array. Each beam varies in length from 1306 to 3194 μm for mimicking the frequency selectivity of the cochlea. To characterize the frequency selectivity of the ABM, we measured the mechanical displacement and piezoelectric output while applying acoustic stimulus at 100 dB sound pressure level in the range of 500 Hz–40 kHz. The resonance frequencies measured by mechanical displacement and piezoelectric output were in the range of 10.56–36.5 and 10.9–37.0 kHz, respectively. In addition, the electrical stimulus was applied to the ABMs to compare the mechanical responses in air and fluid. The measured resonance frequencies were in the range of 11.1–47.7 kHz in the air and 3.10–11.9 kHz in the fluid. Understanding the characteristics of the ABM is important for its potential use as a key technology for auditory prostheses.

Microprobes are used to repair neuronal injury by recording electrical signals from neuronal cells around the surface of the device. Following implantation into the brain, the immune response results in formation of scar tissue around the microprobe. However, neurons must be in close proximity to the microprobe to enable signal recording. A common reason for failure of microprobes is impaired signal recording due to scar tissue, which is not related to the microprobe itself. Therefore, the device–cell interface must be improved to increase the number of neurons in contact with the surface. In this study, we developed nanostructured SU-8 microprobes to support neuronal growth. Nanostructures of 200 nm diameter and depth were applied to the surface of microprobes, and the attachment and neurite outgrowth of PC12 cells on the microprobes were evaluated. Neuronal attachment and neurite outgrowth on the nanostructured microprobes were significantly greater than those on non-nanostructured microprobes. The enhanced neuronal attachment and neurite outgrowth on the nanostructured microprobes occurred in the absence of an adhesive coating, such as poly-l-lysine, and so may be useful for implantable devices for long-term use. Therefore, nanostructured microprobes can be implanted without adhesive coating, which can cause problems in vivo over the long term.

We investigate the effect of electric field on VO2back-gated field effect transistor (FET) devices. Using hybrid dielectric layers, we demonstrate the highest resistance modulation on the order of 102in VO2at a positive gate bias of 80 V (1.6 MV/cm). VO2FET devices are prepared on SiO2substrates of different thicknesses (100–300 nm) and hybrid dielectric layers of Al2O3/SiO2(500 nm). For thicknesses less than 300 nm, no electric-field effects are observed, whereas for a 300 nm thickness, a small decrease in resistance is observed under a 0.2 MV/cm electric field. Under the electrostatic effect, the carrier concentration increases in VO2devices, decreasing the resistance and the transition temperature from 66.75 to 64 °C. The leakage analysis shows that the interface quality of VO2films on hybrid dielectric layers can be further improved. These studies suggest a multilevel fast resistance switching with the electric field and give an insight into the gate-source leakage current, which limits the phase transition in VO2in an electric field.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely employed in biomedical fields, including targeted delivery of antitumor therapy. Conventional magnetic tumor targeting has used simple static magnetic fields (SMFs), which cause SPIONs to linearly aggregate into a long chain-like shape. Such agglomeration greatly hinders the intracellular targeting of SPIONs into tumors, thus reducing the therapeutic efficacy. In this study, we investigated the enhancement of the intracellular uptake of SPIONs through the application of rotating magnetic fields (RMFs). Based on the physical principles of SPION chain disassembly, we investigated physical parameters to predict the chain length favorable for intracellular uptake. Our prediction was validated by clear visualization of the intracellular distributions of SPIONs in tumor cells at both cellular and three-dimensionalmicrotissue levels. To identify the potential therapeutic effects of enhanced intracellular uptake, magnetic hyperthermia as antitumor therapy was investigated under varying conditions of magnetic hyperthermia and RMFs. The results showed that enhanced intracellular uptake reduced magnetic hyperthermia time and strength as well as particle concentration. The proposed method will be useful in the development of techniques to determine the optimized physical conditions for the enhanced intracellular uptake of SPIONs in antitumor therapy.

A magneto-mechano-electric (MME) generator that converts an ambient magnetic field to useable electricity has the potential as an autonomous power source for sensor networks without or supporting driving batteries. However, the output of a typical MME generator decreases when temperature changes lead to resonant frequency drift of the generator. Herein, a broadband MME generator having self-resonance tunability with a movable proof mass was described for continuously generating stable output energy over a range of surrounding temperatures. The designed MME generator with a movable proof mass presented a wide bandwidth of 14.7 Hz, which was 865 % compared to that of a typical MME generator with a fixed proof mass (1.7 Hz). Owing to the self-resonance tunability, the broadband MME generator presented a lower output degradation (0.7 vs. 2.1 mW for a typical MME generator), even when the temperature changed from −30 °C to 60 °C. Under temperature variation, the broadband MME generator generated stable output energy that was sufficient to continuously operate the IoT sensors and maintain the brightness of 120 white LEDs with high intensity. Thus, the MME generator with self-resonance tunability is anticipated to provide a stable energy source, even under harsh environments that induce variable resonant frequency.

The performance of superparamagnetic polymer composite microdevices is highly dependent on the magnetic particle content. While high loading levels are desired for many applications, the UV absorption of these nanoparticles limits the overall thickness of the fabricated microstructures and subsequently their capability of magnetic interaction. The combination of a visible-light-sensitive photoinitiator and particle self-organization is proposed to extend the exposure depth limitation in Epon SU-8 based superparamagnetic polymer composites. While superparamagnetic iron oxide particles strongly absorb i-line radiation required to cross-link the Epon SU-8 polymer matrix, we propose the utilization of H-Nu 470 photoinitiator to expand the photosensitivity of the composite toward the visible spectrum, where the dispersed nanoparticles are more transparent. The novel photoinitiator preserves the composite’s superparamagnetic properties as well as a homogeneous particle distribution. As a result, particle load or resist thickness can be more than doubled while maintaining exposure time. The self-organization of ordered magnetic structures allows for an additional increase in exposure depth of up to 40%, resulting in a 2.5-fold saturation magnetization.

Robotic magnetic manipulation systems offer a wide range of potential benefits in medical fields, such as precise and selective manipulation of magnetically responsive instruments in difficult‐to‐reach vessels and tissues. However, more preclinical/clinical studies are necessary before robotic magnetic interventional systems can be widely adopted. In this study, a clinically translatable, electromagnetically controllable microrobotic interventional system (ECMIS) that assists a physician in remotely manipulating and controlling microdiameter guidewires in real time, is reported. The ECMIS comprises a microrobotic guidewire capable of active magnetic steering under low‐strength magnetic fields, a human‐scale electromagnetic actuation (EMA) system, a biplane X‐ray imaging system, and a remote guidewire/catheter advancer unit. The proposed ECMIS demonstrates targeted real‐time cardiovascular interventions in vascular phantoms through precise and rapid control of the microrobotic guidewire under EMA. Further, the potential clinical effectiveness of the ECMIS for real‐time cardiovascular interventions is investigated through preclinical studies in coronary, iliac, and renal arteries of swine models in vivo, where the magnetic steering of the microrobotic guidewire and control of other ECMIS modules are teleoperated by operators in a separate control booth with X‐ray shielding. The proposed ECMIS can help medical physicians optimally manipulate interventional devices such as guidewires under minimal radiation exposure. The clinically translatable, electromagnetically controllable microrobotic interventional system (ECMIS) comprises a microrobotic guidewire capable of active magnetic steering, a human‐scale electromagnetic actuation system, a biplane X‐ray imaging system, and a remote master–slave advancer unit. The ECMIS assists a physician to remotely control microdiameter interventional tools precisely and instantly in a real‐time manner while being protected from ionizing radiation.

Medical Robotics In article number 2102529by Hongsoo Choi and co‐workers, a proposed electromagnetically controllable microrobotic system can help interventional medical practitioners optimally manipulate interventional devices such as guidewires for the treatment of cardiovascular diseases. The system can be teleoperated, protecting medical staff from ionizing radiation.

We report an experimental assessment of the electrical performance of two piezoelectric beam arrays for artificial basilar membranes (ABMs): a continuous beam array (CBA) and a narrow-supports beam array (NSBA). Both arrays consist of piezoelectric beams of sequentially varying lengths that mimic the frequency selectivity of mammalian cochleae. The narrow supports of the NSBA resulted in lateral deformation of the beams, whereas the CBA beams were flat. The displacement and piezoelectric output of each beam were measured at the resonance frequency of each beam using a scanning laser-Doppler vibrometer (SLDV). Both ABM prototypes showed mechanical frequency selectivity that depended on the beam length. The CBA generated a piezoelectric output in the range 6.6–23.2 μV and exhibited electrical frequency separability, whereas the NSBA failed to generate sufficient electrical potential due to the lateral deformation of the piezoelectric beams. The CBA was found to be more effective as an ABM, with potential for use in cochlear implants.

Electrodeposition is a versatile method, which enables the fabrication of a variety of wire-like nanoarchitectures such as nanowires, nanorods, and nanotubes. By means of template-assisted electrodeposition, segmented Au/Co/Au nanowires are grown in anodic aluminum oxide templates from two different electrolytes. To tailor the properties of the cobalt segments, several electrochemical conditions are studied as a function of current density, pulse deposition, and pH. The morphology, crystal structure, and magnetic properties are accordingly investigated. Changes in the deposition conditions affect the cobalt electrocrystallization process directly. Cobalt tends to crystallize mainly in the hexagonal close-packed structure, which is the reason cobalt might not accommodate satisfactorily on the face-centered cubic Au surface or vice versa. We demonstrate that by modifying the electrolyte and the applied current densities, changes in the texture and the crystalline structure of cobalt lead to a good quality connection between dissimilar segments. In particular, lowering the bath pH, or using pulse plating at a high overpotential, produces polycrystalline fcc Co and thus well-connected Co/Au bimetallic junctions with smooth interface. These are crucial factors to be carefully considered taking into account that nanowires are potential building blocks in micro- and nanoelectromechanical systems.

Thick polycrystalline pure PbTiO3films with nano size grains were synthesized for the first time by aerosol deposition. Annealed 7 μm thick films exhibit well-saturated ferroelectric hysteresis loops with a remanent polarization and coercive field of 35 μC/cm2and 94 kV/cm, respectively. A large-signal effective d33,effvalue of >60 pm/V is achieved at room temperature. The measured ferroelectric transition temperature (Tc) of the films ∼550 °C is >50 °C higher than the reported values (∼490 °C) for PbTiO3ceramics. First-principles calculations combined with electron energy loss spectroscopy (EELS) and structural analysis indicate that the film is composed of nano size grains with slightly decreased tetragonality. There is no severe off-stoichiometry, but a high compressive in-plane residual stress was observed in the film along with a high transition temperature and piezoelectric response. The ferroelectric characteristics were sustained until 200 °C, providing significant advancement toward realizing high temperature piezoelectric materials.

In this study, a one-dimensional beam array acoustic sensor was built using microelectromechanical system technology to achieve mechanical frequency selectivity. The acoustic sensor contained 16 beams of various lengths. The frequency selectivity was evaluated with a scanning laser Doppler vibrometer, while applying an alternating current having various frequencies with 2 volts amplitude and 0 volt offset. The beams formed separate band-pass filters in the proximity of the corresponding resonance frequencies in the range of 3 kHz to 13 kHz. The first resonance frequencies of the beams were calculated using finite element analysis to simulate the frequency response. In the finite element analysis models, mode shapes were studied to understand the effect of the beam deformation caused by the residual stress generated during the MEMS fabrication. The measured and simulated first resonance frequencies of the beams provided solid evidence of the tonotopicity of the sensor.

Microrobots In article number 2100801by Sung Won Kim, Hongsoo Choi, and co‐workers, a magnetically powered stem cell‐based microrobot (named Cellbot) is proposed for the minimally invasive targeted delivery of stem cells to the brain via the intranasal passage. The Cellbot is developed by internalizing superparamagnetic iron oxide nanoparticles into human turbinate stem cells. This approach has the potential to effectively treat central nervous system disorders in a minimally invasive manner.

Targeted stem cell delivery with microrobots has emerged as a potential alternative therapeutic strategy in regenerative medicine, and intranasal administration is an effective approach for minimally invasive delivery of therapeutic agents into the brain. In this study, a magnetically powered stem cell‐based microrobot (“Cellbot”) is used for minimally invasive targeted stem cell delivery to the brain through the intranasal passage. The Cellbot is developed by internalizing superparamagnetic iron oxide nanoparticles (SPIONs) into human nasal turbinate stem cells. The SPIONs have no influence on hNTSC characteristics, including morphology, cell viability, and neuronal differentiation. The Cellbots are capable of proliferation and differentiation into neurons, neural precursor cells, and neurogliocytes. The Cellbots in the microfluidic channel can be reliably manipulated by an external magnetic field for orientation and position control. Using an ex vivo model based on brain organoids, it is determined that the Cellbots can be transplanted into brain tissue. Using a murine model, it is demonstrated that the Cellbots can be intranasally administered and magnetically guided to the target tissue in vivo. This approach has the potential to effectively treat central nervous system disorders in a minimally invasive manner. Intranasal administration of magnetically powered stem cell‐based microrobot is a novel strategy to deliver stem cells into the brain in a targeted and minimally invasive manner. The magnetically actuated stem cell‐based microrobots demonstrate engraftment onto a micro‐brain organoid and into the mouse brain. These techniques may be further developed to effectively treat central nervous system disorders.

Therapeutic agents, such as drugs and cells, play an essential role in virtually every treatment of injury, illness, or disease. However, the conventional practices of drug delivery often result in undesirable side effects caused by drug overdose and off‐target delivery. In the case of cell delivery, the survival rate of the transplanted cells is extremely low and difficulties with the administration route of cells remain a problem. Recently, magnetically actuated microrobots have started offering unique opportunities in targeted therapeutic delivery due to their tiny size and ability to access hard‐to‐reach lesions in a minimally invasive manner; considerable advances in this regard have been made over the past decade. Here, recent progress in magnetically actuated microrobots, developed for targeted drug/cell delivery, is presented, with a focus on their design features and mechanisms for controlled therapeutic release. Additionally, the practical challenges faced by the microrobots, and future research directions toward the swift bench‐to‐bedside translation of the microrobots are addressed. This work reviews recent progress in magnetically controlled medical microrobots developed for targeted delivery of therapeutic agents, such as drugs and cells, with special emphasis on various types of microrobot designs and strategies for controlling drug/cell release. Additionally, practical challenges and future research directions toward the clinical translation of the microrobots are addressed.

Microrobots for targeted drug delivery are of great interest due to their minimal invasiveness and wireless controllability. Here, a magnetically driven porous degradable microrobot (PDM) is reported that consists of a 3D printed helical soft polymeric chassis made of a poly(ethylene glycol) diacrylate and pentaerythritol triacrylate matrix containing magnetite nanoparticles and the anticancer drug 5‐fluorouracil (5‐FU). The encapsulated Fe3O4nanoparticles render the PDM a precise wireless magnetic actuation by means of rotating magnetic fields (RMFs). The increased surface area of the porous PDM facilitates the acoustically induced drug release due to a higher response to the acoustic energy. The drug release profile from the PDM can be selected on command from three different modes, referred to herein as natural, burst, and constant, by differentiating the ultrasound exposure condition. Finally, in vitro test results reveal different therapeutic results for each release mode. The observed great reduction of cancer cell viability in the burst‐ and constant‐release modes confirms that ultrasound with the proposed PDM can enhance the therapeutic effect by increasing drug concentration and sonoporation. A porous degradable microrobot (PDM), which encapsulates Fe3O4nanoparticles and 5‐fluorouracil, is fabricated using a two‐photon polymerization (TPP) technique. A rotating magnetic field (RMF) is used for remote manipulation of the PDM, and three different ultrasonic release modes (natural, burst, and constant) are investigated. Corresponding in vitro cell viability tests establish the therapeutic feasibility of PDM‐ultrasound mediated therapy.

A needle‐type microrobot (MR) for targeted drug delivery is developed to stably deliver drugs to a target microtissue (MT) for a given period time without the need for an external force after affixing. The MRs are fabricatedby 3D laser lithography and nickel (Ni)/titanium oxide (TiO2) layers are coated by physical vapor deposition. The translational velocity of the MR is 714 µm s−1at 20 mT and affixed to the target MT under the control of a rotating magnetic field. The manipulability of the MR is shown by using both manual and automatic controls. Finally, drug release from the paclitaxel‐loaded MR is characterized to determine the efficiency of targeted drug delivery. This study demonstrates the utility of the proposed needle‐type MR for targeted drug delivery to MT with various flow rates in vitro physiological fluidic environments. A needle‐type microrobot is fabricated by 3D laser lithography for stable drug delivery. The drug‐loaded microrobot can be fixed to a target microtissue by swimming in a corkscrew motion under a rotating magnetic field. The results demonstrate the potential of the needle‐type microrobot to improve targeted drug delivery to microtissue with various flow rates in vitro physiological fluidic environments.

In article number 1901697by Hongsoo Choi and co‐workers, a drug‐loaded micro‐robot can be attached to a target micro‐tissue by swimming in a corkscrew motion with magnetic torque under a rotating magnetic field. The needle‐type micro‐robot has the potential to improve targeted drug delivery to a micro‐tissue in vitro in physiological fluid environments.

In article number 1900739by Hongsoo Choi, Dong‐Pyo Kim, and co‐workers, biocompatible ceramic microrobots are developed for cell delivery for the first time. The microrobots are fabricated by 3D laser lithography, and magnetic nanoparticles are immobilized on the surface of the microrobots to manipulate the movement of the microrobots by an external magnetic field.

A silicon carbonitride (SICN) ceramic microrobot, biocompatible and magnetically activable, is developed for the delivery of viable cells to defective tissue by sequential steps of microstructuring, magnetization, and cell loading. The ceramic carrier of porous cylindrical framework is fabricated by 3D laser lithography using a photocurable preceramic polymer, chemically modified polyvinylsilazane, and subsequent pyrolysis at 600 °C under an inert atmosphere. Magnetic nanoparticles (MNP) are integrated into the surface‐modified ceramic carrier by thiol‐ene click reaction. Finally, the microrobot is loaded with fibroblast cells, which can be guided by a rotating external magnetic field. The proposed ceramic microrobot is mechanically durable, adequately controllable with external magnetic field, and quite compatible with mammalian cells. Biocompatible magnetically actuated silicon carbonitride ceramic microrobots are developed for biomedical applications. The microrobots are fabricated by 3D laser lithography using a photocurable preceramic polymer and converted to ceramics by subsequent pyrolysis. Magnetic nanoparticles are integrated onto the surface for magnetic actuation. The microrobots loaded with fibroblast cells are actuated with directionality by an external magnetic field.

In cochlear implants, the electrode insertion trauma during surgery can cause damage residual hearing. Preserving the residual hearing is an important challenge and the localized administration of drugs, such as steroids, is one of the most promising ways, but remains a challenge. Here, a microscaffold cochlear electrode array (MiSCEA) consisting of a microfabricated flexible electrode array and a 3D microscaffold for steroid reservoir is reported. The MiSCEA without loaded drug is tested by measuring the electrically evoked auditory brainstem response of the cochlea in guinea pigs (n= 4). The scaffold is then coated with steroid (dexamethasone) encapsulated in polylactic‐co‐glycolic acid and the continuous release of the steroid into artificial perilymph during six weeks is monitored. The steroid‐containing scaffolds are then implanted into guinea pigs (n= 4) and threshold shifts are analyzed for four weeks by measuring the acoustically evoked auditory brainstem response. The threshold shifts tend to be lower in the group implanted with the steroid‐containing MiSCEAs. The feasibility of 3D MiSCEA opens up the development of potential next‐generation cochlear electrode with improved steroid release dynamics into cochlea. A microscaffold cochlear electrode array (MiSCEA) consisting of a microfabricated flexible electrode array and a 3D microscaffold for steroid reservoir is developed. The MiSCEA coating steroid (dexamethasone) encapsulated in polylactic‐co‐glycolic acid is implanted into cochlea of guinea pigs and the hearing threshold shifts after four weeks tend to be lower than the MiSCEA without coating steroid.

Microrobots facilitate targeted therapy due to their small size, minimal invasiveness, and precise wireless control. A degradable hyperthermia microrobot (DHM) with a 3D helical structure is developed, enabling actively controlled drug delivery, release, and hyperthermia therapy. The microrobot is made of poly(ethylene glycol) diacrylate (PEGDA) and pentaerythritol triacrylate (PETA) and contains magnetic Fe3O4nanoparticles (MNPs) and 5‐fluorouracil (5‐FU). Its locomotion is remotely and precisely controlled by a rotating magnetic field (RMF) generated by an electromagnetic actuation system. Drug‐free DHMs reduce the viability of cancer cells by elevating the temperature under an alternating magnetic field (AMF), a hyperthermic effect. 5‐FU is released from the proposed DHMs in normal‐, high‐burst‐, and constant‐release modes, controlled by the AMF. Finally, actively controlled drug release from the DHMs in normal‐ and high‐burst‐release mode results in a reduction in cell viability. The reduction in cell viability is of greater magnitude in high‐burst‐ than in normal‐release mode. In summary, biodegradable DHMs have potential for actively controlled drug release and hyperthermia therapy. A degradable hyperthermia microrobot (DHM), whichencapsulates 5‐fluorouracil and Fe3O4nanoparticles is developed and demonstrates the potential for actively controlled drug release and hyperthermia therapy. The locomotion of the DHM is remotely controlled by a rotating magnetic field. The alternating magnetic field not only increases the temperature of the DHMs, but also actively controls the drug release from the DHMs.

A capsule‐type microrobot exhibits “pick‐and‐drop” (P&D) motion to hold a particle within a confined volume and transports it via a corkscrewing motion. The P&D motion is possible because the capsule‐type microrobot has two parts: a plunger and a cap. The fabricated microrobots are wirelessly controlled by a magnetic manipulator. Drugs or cells can be encapsulated in the container of the capsule‐type microrobot by the P&D motion or attached to the surface of the cap, which can be used as a supporting structure. Therefore, the capsule‐type microrobot can deliver suspended or adherent cells. The drug or cells are minimally exposed or not completely exposed to the surrounding fluid and do not experience shear force when encapsulated in the container. As a proof‐of‐concept, secure transportation of microparticles in the confined volume of the capsule via P&D motion is demonstrated. In addition, the cap is used as a scaffold for neuronal cell culture on a rat brain slice to demonstrate its biocompatibility and feasibility for targeted cell delivery. The proposed capsule‐type microrobot is suitable for diverse applications, as it protects the encapsulated materials. A capsule‐type microrobot exhibits “pick‐and‐drop” (P&D) motionto hold a particle within a confined volume and transport it via a corkscrewing motion. Drugs or cells can be encapsulated in the container of the microrobot by the P&D motion or attached to the surface of the cap, which can be used as a supporting structure.

A capsule‐type microrobot exhibits “Pick‐and‐Drop” (P&D) motion for possible drug and cell transport via a corkscrew motion. Drugs or cells can be encapsulated in the microrobot's container by the P&D motion or attached to the surface of the cap, which can be used as a cell supporting structure. This work is discussed in article number 1700985by Hongsoo Choi and co‐workers.

Patients with sensorineural hearing loss can recover their hearing using a cochlear implant (CI). However, there is a need to develop next‐generation CIs to overcome the limitations of conventional CIs caused by extracorporeal devices. Recently, artificial basilar membranes (ABMs) are actively studied for next‐generation CIs. The ABM is an acoustic transducer that mimics the mechanical frequency selectivity of the BM and acoustic‐to‐electrical energy conversion of hair cells. This paper presents recent progress in biomimetic ABMs. First, the characteristics of frequency selectivity of the ABMs by the trapezoidal membrane and beam array are addressed. Second, to reflect the latest research of energy conversion technologies, ABMs using various piezoelectric materials and triboelectric‐based ABMs are discussed. Third, in vivo evaluations of the ABMs in animal models are discussed according to the target position for implantation. Finally, future perspectives of ABM studies for the development of practical hearing devices are discussed. Artificial basilar membrane (ABM)is an acoustic transducer that mimics cochlear tonotopy. This Progress Report provides a brief review of the ABMs for next‐generation cochlear implants. The scope includes tonotopic characteristics of the ABM, in vivo experiments using animal models, and future perspectives of the ABM for next‐generation cochlear implants.

Artificial basilar membrane (ABM) is an acoustic transducer that mimics cochlear tonotopy. In article number 1700674, Hongsoo Choi and co‐workers demonstrate how mechanical‐to‐electrical transduction can be implemented by the piezoelectric or triboelectric effect for self‐powered devices. The ABMs are currently evolving into practical hearing sensors and will be the key technology that opens up the development of next generation cochlear implants in near future.