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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

Implantable sensors can be used to monitor biomechanical strain continuously. However, three key challenges need to be addressed before they can be of use in clinical practice: the structural mismatch between the sensors and tissue or organs should be eliminated; a practical suturing attachment process should be developed; and the sensors should be equipped with wireless readout. Here, we report a wireless and suturable fibre strain-sensing system created by combining a capacitive fibre strain sensor with an inductive coil for wireless readout. The sensor is composed of two stretchable conductive fibres organized in a double helical structure with an empty core, and has a sensitivity of around 12. Mathematical analysis and simulation of the sensor can effectively predict its capacitive response and can be used to modulate performance according to the intended application. To illustrate the capabilities of the system, we use it to perform strain measurements on the Achilles tendon and knee ligament in an ex vivo and in vivo porcine leg. A capacitive, fibre-like stretchable strain sensor, formed of two conductors in a double helical structure, can be combined with an inductive coil to create a wireless strain-sensing system for biomedical applications.

This brief presents a high voltage modular supply multiplying pulser in a 0.18- $\mu m$ BCD CMOS process. Two prototypes of the pulser were implemented for target loads of 55pF and 1nF, and generated up to 1MHz and 28.7V pulse from 1.2 and 5V supplies. Proposed modular based stepwise pulse generation achieved a peak power reduction of 75.4% relative to CV 2 f and a peak power efficiency of 82.3%. The proposed pulser was used for driving piezoelectric micromachined ultrasound transducer (pMUT) and achieved a relative efficiency improvement of 113.7% against conventional two-level square wave pulsing.

To fundamentally solve the bottleneck of Von Neumann’s computing architecture, a neuromorphic thin-film transistor (NTFT) employing Pb(Zr, Ti)O3 (PZT) was investigated. The indium gallium zinc oxide (IGZO) channel back gate TFT structure was chosen to solve the diffusion of atoms that form a channel layer during the annealing process for crystallization of PZT. A post-deposition process with IGZO after annealing PZT and using an oxide-based material as a channel structure can minimize the diffusion phenomenon of junction materials and oxygen together, which leads to a high and reliable performance of the NTFT. The basic operations of synapses short-term memory (STM) and long-term memory (LTM) were also analyzed to confirm the application of a neuromorphic device. The high dielectric constant and polarization properties of Pb(Zr, Ti)O3 (PZT) allow the power consumption of spike signals used in spike dependent plasticity change to be reduced to 10 pJ. Moreover, a wide dynamic range of $\text{G}_{\mathrm {max}}/\text{G}_{\mathrm {min}} \cong ~1000$ was obtained, and the channel conductance was maintained over 40000 seconds. The optimized pulse achieved multi-level states (>32), which made the learning process efficient. This study verified that the PZT-TFT structure has a high potential and merits for neuromorphic devices.

A great deal of research has focused on small-scale robots for biomedical applications and minimally invasive delivery of therapeutics (e.g., cells, drugs, and genes) to a target area. Conventional fabrication methods, such as two-photon polymerization, can be used to build sophisticated micro- and nanorobots, but the long fabrication cycle for a single microrobot has limited its practical use. This study proposes a biodegradable spherical gelatin methacrylate (GelMA) microrobot for mass production in a microfluidic channel. The proposed microrobot is fabricated in a flow-focusing droplet generator by shearing a mixture of GelMA, photoinitiator, and superparamagnetic iron oxide nanoparticles (SPIONs) with a mixture of oil and surfactant. Human nasal turbinate stem cells (hNTSCs) are loaded on the GelMA microrobot, and the hNTSC-loaded microrobot shows precise rolling motion in response to an external rotating magnetic field. The microrobot is enzymatically degraded by collagenase, and released hNTSCs are proliferated and differentiated into neuronal cells. In addition, the feasibility of the GelMA microrobot as a cell therapeutic delivery system is investigated by measuring electrophysiological activity on a multielectrode array. Such a versatile and fully biodegradable microrobot has the potential for targeted stem cell delivery, proliferation, and differentiation for stem cell-based therapy. ISSN:1613-6810 ISSN:1613-6829

Objective: Interventional ultrasound imaging is a prerequisite for guiding implants and treatment within the hearts and blood vessels. Due to limitations on the catheter's diameter, interventional ultrasonic transducers have side-looking structures although forward-looking imaging may provide more intuitive and real time guidance in treating diseased sites ahead of catheters. To address the issue, a magnetically actuated forward-looking interventional ultrasound imaging device is implemented for the first time. Methods: A forward-looking catheter containing a 1 mm ring type focused 35 MHz ultrasound transducer and a micro magnet, was fabricated. For imaging, the transducer was placed at the center of four electromagnetic coils positioned on four sides of a squared acrylic housing. By modifying the magnetic field, the catheter tip could be remotely translated for sector scanning. Results: The scanning angle could reach up to 3° in 1 Hz with 15 mT, while wider angles of 5° could be achieved with a higher magnetic field of 25 mT for ex-vivo imaging. The position of the transducer could be detected by monitoring the motion with a CCD camera, mimicking clinical X-ray imaging. In the wire target and tissue mimicking phantom studies, the measured hole size, spatial resolution and distance between wires by the proposed system were comparable with the values from a linear scanner. Multi-frame real time data acquisition was demonstrated via ex-vivo imaging on a pig's coronary artery. Conclusion/Significance: The feasibility of magnetically actuated forward-looking interventional ultrasound imaging was demonstrated. The remote-controlled scanning method may allow to simplify the structures of forward-looking interventional ultrasound imaging catheters.

Magnetic actuation techniques and microrobots have attracted considerable interest due to their potential applications in biomedicine. Interventional techniques have emerged as a minimally invasive approach to treat a wide range of vascular diseases. The current practice of interventional procedures is, however, limited by manual control of interventional devices and time-consuming procedures. Moreover, fluoroscopy is considered as an essential part of the procedure today despite posing many limitations for patients and physicians. Recently, various microrobotic solutions have been proposed for vascular interventions, including advances in magnetic navigation systems and magnetically steerable catheters and guidewires, which have shown potential benefits such as reduced radiation doses, improved access to difficult-to-reach and tortuous anatomy. This paper reviews the commercial magnetic actuation systems and magnetically actuated interventional microrobots that have been developed by academic research groups and medical companies worldwide, outlining their capability, applicability as well as limitations. We further address the challenges and future prospects of the research toward clinical acceptance of magnetic interventional technologies.

A vector hydrophone is an underwater acoustic sensor that can detect the direction of a sound source. Wide-band characteristics and high sensitivity enhance the performance of underwater surveillance systems in complex environments. A vector hydrophone comprising a triaxial piezoelectric accelerometer and spherical hydrophone was fabricated and tested in the air and underwater. The vector hydrophone was designed to exceed the quantitative figures of merit (i.e., receiving voltage sensitivity and bandwidth) of commercially available hydrophones. Accelerometer performance was enhanced by placing a pair of piezoelectric single crystals on each axis and modifying the seismic mass material. The receiving voltage sensitivity of the omnidirectional hydrophone was approximately −160 dB relative to 1V/μPa with the amplifier in water; the sensitivity of the accelerometer exceeded 300 mV/g in air and −215 dB relative to 1V/μPa underwater over the frequency range of interest. The receiving directivity of the vector hydrophone was validated underwater, which confirmed that it could detect the direction of a sound source.

For the safety and efficacy of in vivo therapy using electromagnetic actuated microrobots, position tracking performance is crucially important. However, it is difficult to manipulate the microrobots accurately and rapidly due to the nonlinear and complex dynamics of the microrobots and highly limited magnetic force of the actuator. In this paper, we propose a robust control law for the microrobots. It consists of a time-delay estimation to compensate for the unknown/unmodeled dynamics, an antiwindup scheme, and a forgetting factor to improve the performance. In addition, we added a switching action to the control law in order to guarantee the stability of the controller. The improved performance and stability of the proposed control law were verified through an experiment that contains 3-DOF motion.

Magnetically actuated soft robots may improve the treatment of disseminated intravascular coagulation. Significant progress has been made in the development of soft robotic systems that steer catheters. A more challenging task, however, is the development of systems that steer sub-millimeter-diameter guidewires during intravascular treatments; a novel microrobotic approach is required for steering. In this article, we develop a novel, magnetically actuated, soft microrobotic system, increasing the steerability of a conventional guidewire. The soft microrobot is attached to the tip of the guidewire, and it is magnetically steered by changing the direction and intensity of an external magnetic field. The microrobot is fabricated via replica molding and features a soft body made of polydimethylsiloxane, two permanent magnets, and a microspring. We developed a mathematical model mapping deformation of the soft microrobot using a feed-forward approach toward steering. Then, we used the model to steer a guidewire. The angulation of the microrobot can be controlled from 21.1° to 132.7° by using a magnetic field of an intensity of 15 mT. Steerability was confirmed by two-dimensional in vitro tracking. Finally, a guidewire with the soft microrobot was tested by using a three-dimensional (3D) phantom of the coronary artery to verify steerability in 3D space.

All-solid-state batteries (ASSBs) based on solid-state electrolytes (SSEs) are receiving significant interest as promising candidates to overcome the limitations of conventional lithium ion batteries (LIBs), particularly safety problems. Development of operando or in situ microscopy and spectroscopy measurement techniques is crucial for real-time observations of the morphological and chemical phenomena occurring in ASSBs during charge/discharge cycles. In this study, we develop in situ Auger electron microscopy and spectroscopy techniques for real-time investigations of the various phenomena occurring in ASSBs based on pelletized argyrodite (Li6PS5Cl; LiPS) SSEs. Volume expansion/contraction of the Li metal anode owing to the injection/extraction of Li is observed during the charge/discharge process. Li migration to the Li metal anode is strongly dependent on the pressing force applied to the sample during the charge/discharge cycles. At the sample position under excessively high local pressure, a superabundant amount of Li metal migrates to the anode, and irreversible growth of Li metal is observed. In contrast, the volume expansion of the Li metal anode is negligible at the unpressurised sample position, resulting in poor capacity of the ASSBs. This result demonstrates that homogeneous pressurization of the sample is a critical factor for a stable charge/discharge process. The results provided herein can guide the development of practical ASSBs in industry, and the novel in situ measurement technique can be a useful tool for the real-time analysis of various phenomena in ASSBs.

Complete genome sequences of 22 isolates of Cucurbit aphid-borne yellows virus (CABYV), collected from melon plants showing yellowing symptom in Korea during the years 2013–2014, were determined and compared with previously reported CABYV genome sequences. The complete genomes were found to be 5,680–5,684 nucleotides in length and to encode six open reading frames (ORFs) that are separated into two regions by a non-coding internal region (IR) of 199 nucleotides. Their genomic organization is typical of the genus Polerovirus. Based on phylogenetic analyses of complete nucleotide (nt) sequences, CABYV isolates were divided into four groups: Asian, Mediterranean, Taiwanese, and R groups. The Korean CABYV isolates clustered with the Asian group with > 94% nt sequence identity. In contrast, the Korean CABYV isolates shared 87–89% sequence identities with the Mediterranean group, 88% with the Taiwanese group, 81–84% with the CABYV-R group, and 72% with another polerovirus, M.. Recombination analyses identified 24 recombination events (12 different recombination types) in the analyzed CABYV population. In the Korean CABYV isolates, four recombination types were detected from eight isolates. Two recombination types were detected in the IR and P3–P5 regions, respectively, which have been reported as hotspots for recombination of CABYV. This result suggests that recombination is an important evolutionary force in the genetic diversification of CABYV populations.

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.

Animals detect and discriminate countless environmental chemicals for their well-being and survival. Although a single chemical can trigger opposing behavioral responses depending on its concentration, the mechanisms underlying such a concentration-dependent switching remain poorly understood. Here, we show that C. elegans exhibits either attraction or avoidance of the bacteria-derived volatile chemical dimethyl trisulfide (DMTS) depending on its concentration. This behavioral switching is mediated by two different types of chemosensory neurons, both of which express the DMTS-sensitive seven-transmembrane G protein-coupled receptor (GPCR) SRI-14. These two sensory neurons share downstream interneurons that process and translate DMTS signals via distinct glutamate receptors to generate the appropriate behavioral outcome. Thus, our results present one mechanism by which an animal connects two distinct types of chemosensory neurons detecting a common ligand to alternate downstream circuitry, thus efficiently switching between specific behavioral programs based on ligand concentration.

Neutrophil-based microrobots accomplish the mission of crossing the blood-brain barrier for targeted drug delivery.

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.

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.

There has been a great deal of interest in the development of technologies for actively manipulating neural networks in vitro, providing natural but simplified environments in a highly reproducible manner in which to study brain function and related diseases. Platforms for these in vitro neural networks require precise and selective neural connections at the target location, with minimal external influences, and measurement of neural activity to determine how neurons communicate. Here, we report a neuron-loaded microrobot for selective connection of neural networks via precise delivery to a gap between two neural clusters by an external magnetic field. In addition, the extracellular action potential was propagated from one cluster to the other through the neurons on the microrobot. The proposed technique shows the potential for use in experiments to understand how neurons communicate in the neural network by actively connecting neural clusters.

Background: Clinically, steroids have been used for hearing preservation both topically and systemically during cochlear implantation.Objective: This study compared steroid efficacy for hearing pre...

Magnetic microrobots have potential use in biomedical applications such as minimally invasive surgery targeted diagnosis and therapy. Inspired by nature artificial bacterial flagella (ABFs) are a form of microrobot powered by magnetic helical propulsion. For the promise of ABFs to be realized issues of biocompatibility must be addressed and the materials used in their fabrication should be carefully considered. In this work we fabricate the helical bodies of ABFs from a commercially available biocompatible photoresist ORMOCOMP by subsequently coating them with Fe for magnetic actuation. 3 (45 Dimethylthiazol 2 yl) 25 diphenyltetrazolium bromide (MTT) assays show that Fe coated ORMOCOMP layers do not undermine the cell viability during 72 hours of incubation compared to control substrates. Cells exhibit normal morphology on ABF arrays and show good lamellipodial and filopodial interactions with the ABF surfaces. The swimming performance of Fe coated ABFs is characterized using a three pair Helmholtz coil arrangement. ABFs exhibit a maximum forward speed of 48.9 µm s 1 under a field of 9 mT at a frequency of 72 Hz. In summary our Fe coated ABFs exhibit little cytotoxicity and have potential for in vivo applications especially those involving difficult to access regions within the human body. © 2014 The Royal Society of Chemistry.

In this study, we have established 5 different micro-organs (Cortex-Hippocampus-Heat-Liver-Tumor) network in vitro in the 96-well format-based microfluidic platform by physically separating but fluidically interconnecting spherical microtissues (MTs) via the microfluidic channel. An effect of the anti-cancer drug, 5-fluorouaracil (5-FU), on tumor MT and also other organotypic MTs was investigated with their interaction through microfluidic network in vitro for 3-day cultivation While no significant suppression was observed when tumor MTs were solely cultured in 5-FU, growth of tumor MTs was suppressed in the in vitro 5 micro-organ network without critical impact on the other 4 MTs. It addresses feasibility of our microfluidic platform for more complex and comprehensive pharmacokinetic study in an in vivo-like in vitro physiological environment.

Here, we propose magnetically driven microrobots for targeted cell delivery that can efficiently swim in various physiological environments. The three-dimensional (3D) microrobots were sophisticatedly fabricated by using micro-electro-mechanical systems (MEMS) technologies such as 3D laser lithography and metal sputtering. The magnetic field generated by an electromagnetic coil system allows efficient wireless actuation of the microrobots, which was characterized in various physiological conditions (in vitro viscous fluid, ex vivo rat brain blood vessels and a live nude mouse intraperitoneal cavity (in vivo)). Especially, the microrobots demonstrated stem cell transportation inside the body cavity of the nude mouse as a proof of concept of targeted cell delivery. Through this study, the use of the proposed microrobots has shown the feasibility of future applications in precision medicine.

The Sweet potato chlorotic fleck virus (SPCFV), of the genus Carlavirus (family Betaflexiviridae), was first detected as one of several viruses infecting sweet potatoes (Ipomea batatas L.) in Korea. Out of 154 sweet potato samples collected in 2012 that were showing virus-like symptoms, 47 (31%) were infected with SPCFV, along with other viruses. The complete genome sequences of four SPCFV isolates were determined and analyzed using previously reported genome sequences. The complete genomes were found to contain 9,104-9,108 nucleotides, excluding the poly-A tail, containing six putative open reading frames (ORFs). Further, the SPCFV Korean isolates were divided into two groups (Group I and Group II) by phylogenetic analysis based on the complete nucleotide sequences; Group I and Group II had low nucleotide sequence identities of about 73%. For the first time, we determined the complete genome sequence for the Group II SPCFV isolates. The amino acid sequence identity in coat proteins (CP) between the two groups was over 90%, whereas the amino acid sequence identity in other proteins was less than 80%. In addition, SPCFV Korean isolates had a low amino acid sequence identity (61% CPs and 47% in the nucleotide- binding protein [NaBp] region) to that of Melon yellowing-associated virus (MYaV), a typical Carlavirus.

Major viruses infecting rice are transmitted by planthoppers such as small brown planthopper (SBPH), brown planthopper (BPH) and white-backed planthopper (WBPH). In this study, we investigated planthoppers captured during 2015 to 2017 by a smart sky net trap (SSNT) system installed in 40 areas in Korea, which is an automatic, rapid and real-time insect surveillance system. The average rates of captured migration plnathoppers was 27.5%, 17.2%, 15.3% and 10.9% in Chungcheongnamdo, Jeollanamdo, Jeollabukdo and Gyeonggido, orderly. The highly migrated month was July for SBPH, July to August for WBPH and August for BPH. To investigate the viruliferous rates of planthoppers of rice during 2015 to 2017, we performed RT-PCR using specific primers for each rice virus. RBSDV was detected from 0.4% in SBPH, while no viruses were detected in BPH and SBPH. Rice planthoppers exist all around in Asia. They can move long distance by wind from southern countries to Korea. Monitoring the migration of rice planthoppers and their viruliferous rates is important to prevent the outbreaks of rice virus diseases.

Magnetically manipulated biodegradable microrobots that encapsulate drugs from the outset are produced in a novel, simple way using UV-laser micro-machining. This method enables multiple microrobots to be produced rapidly, without the need for post-drug encapsulation or polymerization by light exposure, which may cause the drug compound to denature. The microrobot consists of poly (dl-lactic-co-glycolic acid) (PLGA), iron (Fe) particles and 5-fluorouracil (5-FU) as biodegradable, magnetic and drug material, respectively. The fabricated microrobots are precisely and remotely controlled in a fluidic environment by external magnetic fields. To prove the feasibility of targeted drug delivery, the drug release is profiled as a function of time, biodegrading in aqueous solution at 37 °C over 6 weeks. The Fe concentration has a significant effect on the biodegradation rate of the microrobots. The amount of drug encapsulated can be controlled by adjusting the concentration of the drug in the PLGA/Fe/5-FU mixture whilst fabricating the microrobots. Approximately 0.013 μg of 5-FU is released from a single PLGA/Fe/5-FU microrobot over a period of 6 weeks. In addition, we have conducted drug testing with human colorectal cancer (HCT116) cells to investigate the effect of drugs released from our microrobots on cancer cells. While no significant reduction in live cell ratio was observed with the controls, it decreased approximately 20% when cells were cultured with the PLGA/Fe/5-FU microrobot for 2 days. It presents that 5-FU was delivered from the microrobot to cancer cells and negatively affected them.

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-1 at 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.

This paper presents a novel Adaptive Genetic Algorithm for optimal path planning of multiple nanoparticles during the nanomanipulation process. The proposed approach determines the optimal manipulation path in the presence of surface roughness and environment obstacles by considering constraints imposed on the nanomanipulation process. In this research, first by discretizing the environment, an initial set of feasible paths were generated, and then, path optimization was continued in the original continuous environment (and not in the discrete environment). The presented novel approach for path planning in continuous environment (1) makes the algorithm independent of grid size, which is the main limitation in conventional path planning methods, and (2) creates a curve path, instead of piecewise linear one, which increases the accuracy and smoothness of the path considerably. Every path is evaluated based on three factors: the displacement effort (the area under critical force-time diagram during nanomanipulation), surface roughness along the path, and smoothness of the path. Using the weighted linear sum of the mentioned three factors as the objective function provides the opportunity to (1) find a path with optimal value for all factors, (2) increase/decrease the effect of a factor based on process considerations. While the former can be obtained by a simple weight tuning procedure introduced in this paper, the latter can be obtained by increasing/decreasing the weight value associated with a factor. In the case of multiple nanoparticles, a co-evolutionary adaptive algorithm is introduced to find the best destination for each nanoparticle, the best sequence of movement, and optimal path for each nanoparticle. By introducing two new operators, it was shown that the performance of the presented co-evolutionary mechanism outperforms the similar previous works. Finally, the proposed approach was also developed based on a modified Particle Swarm Optimization algorithm, and its performance was compared with the proposed Adaptive Genetic Algorithm.

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.

Vector hydrophones based on a micro-electro-mechanical system (MEMS) hold great promise for underwater communications, due to their potential for miniaturization and mass production. Piezoelectric materials have recently been utilized in the fabrication of MEMS-based vector hydrophones, as less power is typically required for their operation. Here, we propose a millimeter-scale piezoelectric MEMS vector sensor with a suspended cross-shaped beam and a mushroom-shaped proof mass configuration. This design was inspired by the bio-transducer of the lateral line of fish. Sensor fabrication involved piezoelectric Pb(Zr0.52Ti0.48)O3 thin-film deposition by radio-frequency magnetron sputtering onto the beam structure, followed by a multi-etching process and assembly using a three-axis microassembly technique. The fabricated MEMS vector sensor showed a resonance frequency above the working frequency range, which was suitable for naval applications. The directivity of the proposed sensor was determined by dipole patterns in the x and y directions, with a maximum relative sensitivity difference of −42 dB at 1 kHz. Finite element analysis results for the resonance frequency and directivity were in good agreement with the experimental results, suggesting that the proposed vector sensor could be used in underwater communications as a vector hydrophone.

Poly(vinylidene fluoride) (PVDF) and its copolymers have been extensively utilized owing to their fascinating properties such as thermal stability, chemical resistance, and mechanical robustness. However, their lack of microbial resistance is considered a drawback that limits their adoption as biomedical materials. In this study, to overcome this problem, PVDF-based antimicrobial polymers were prepared by grafting quaternary ammonium or quaternary pyridinium monomers. The polymers could effectively kill gram-positive S. aureus, gram-negative E. coli, and the pathogenic yeast C. albicans (antimicrobial rates > 99.99%). Using the polymer blending method, 1 wt% or 5 wt% of the polymers were added to the pristine PVDF film to provide antimicrobial properties. The blend films exhibited enhanced mechanical properties compared to those of pristine PVDF and notably higher antimicrobial performances (>99% for Blend-Q4VP-5); moreover, they were all biocompatible.

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.

Polymeric ionic liquids (PILs) containing a poly(ethylene glycol) methacrylate (POEM) coating layer significantly suppresses the reduction of the ionic liquid and of solvent molecules on Li metal anode in the Pyr14TFSI/carbonate electrolyte. Therefore, when Li metal was coated with the PILs–POEM, a cycling test performed with the electrolyte highlights an improved cycling stability.

We report that ultra-thin tellurium (Te) nanoflakes were successfully grown on a sample of a gold-coated textile, which then was used as an active piezoelectric material. An output voltage of 4 V and a current of 300 nA were obtained from the bending test under a driving frequency of 10 Hz. To test the practical applications, Te nanoflake nanogenerator (TFNG) device was attached to the subject’s arm, and mechanical energy was converted to electrical energy by means of periodic arm-bending motions. The optimized open-circuit voltage and short-circuit current density of approximately 125 V and 17 μA/cm 2 , respectively, were observed when a TFNG device underwent a compression test with a compressive force of 8 N and driving frequency of 10 Hz. This high-power generation enabled the instantaneous powering of 10 green light-emitting diodes that shone without any assistance from an external power source.

An artificial tactile system has attracted tremendous interest and intensive study, since it can be applied as a new functional interface between humans and electronic devices. Unfortunately, most previous works focused on improving the sensitivity of sensors. However, humans also respond to psychological feelings for sensations such as pain, softness, or roughness, which are important factors for interacting with others and objects. Here, we present an electronic skin concept that generates a "pain" warning signal, specifically, to sharp "prick" and "hot" sensations. To simplify the sensor structure for these two feelings, a single-body tactile sensor design is proposed. By exploiting "hot" feeling based on the Seebeck effect instead of the pyroelectric property, it is possible to distinguish points registering a "hot" feeling from those generating a "prick" feeling, which is based on the piezoelectric effect. The control of free carrier concentration in nanowire induced the appropriate level of Seebeck current, which enabled the sensor system to be more reliable. The first derivatives of the piezo and Seebeck output signals are the key factors for the signal processing of the "pain" feeling. The main idea can be applied to mimic other psychological tactile feelings.

Magnetic microrobots were developed for three-dimensional culture and the precise delivery of stem cells in vitro, ex vivo, and in vivo. Hippocampal neural stem cells attached to the microrobots proliferated and differentiated into astrocytes, oligodendrocytes, and neurons. Moreover, microrobots were used to transport colorectal carcinoma cancer cells to tumor microtissue in a body-on-a-chip, which comprised an in vitro liver-tumor microorgan network. The microrobots were also controlled in a mouse brain slice and rat brain blood vessel. Last, microrobots carrying mesenchymal stem cells derived from human nose were manipulated inside the intraperitoneal cavity of a nude mouse. The results indicate the potential of microrobots for the culture and delivery of stem cells.

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 Fe3 O4 nanoparticles (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.

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., Micro and Nano Systems Letters, 6