Static and Dynamic Gradient Based Directional Transportation of Neutral Molecules in Swollen Polymer Films.

Materials which selectively transport molecules offer powerful opportunities for concentrating and separating chemical agents. Here, utilizing static and dynamic chemical gradients, transport of molecules within swollen crosslinked polymers is demonstrated. Using an ≈200 µm static hydroxyl to hexyl gradient, the neutral ambipolar nerve agent surrogate diethyl (cyanomethyl)phosphonate (DECP) is directionally transported and concentrated 60-fold within 4 hours. To accelerate transport kinetics, a dynamic gradient (a "travelling wave") is utilized. Here, the non-polar dye pyrene was transported. The dynamic gradient is generated by an ion exchange process triggered by the localized introduction of an aqueous NaCl solution, which converts the gel from hydrophobic to hydrophilic. As the hydrophilic region expands, associated water enters the gel, and pyrene is pushed ahead of the expansion front. The dynamic gradient provides about 10-fold faster transport kinetics than the static gradient.

Coding, Decoding and Retrieving a Message Using DNA: An Experience from a Brazilian Center Research on DNA Data Storage.

DNA data storage based on synthetic oligonucleotides is a major attraction due to the possibility of storage over long periods. Nowadays, the quantity of data generated has been growing exponentially, and the storage capacity needs to keep pace with the growth caused by new technologies and globalization. Since DNA can hold a large amount of information with a high density and remains stable for hundreds of years, this technology offers a solution for current long-term data centers by reducing energy consumption and physical storage space. Currently, research institutes, technology companies, and universities are making significant efforts to meet the growing need for data storage. DNA data storage is a promising field, especially with the advancement of sequencing techniques and equipment, which now make it possible to read genomes (i.e., to retrieve the information) and process this data easily. To overcome the challenges associated with developing new technologies for DNA data storage, a message encoding and decoding exercise was conducted at a Brazilian research center. The exercise performed consisted of synthesizing oligonucleotides by the phosphoramidite route. An encoded message, using a coding scheme that adheres to DNA sequence constraints, was synthesized. After synthesis, the oligonucleotide was sequenced and decoded, and the information was fully recovered.

Multifunctional Micromachines Constructed by Combining Multiple Protein-Based Components with Different Functions.

Untethered mobile micromachines have considerable potential to realize more effective and minimally invasive medicine. Although diverse medical micromachines have been reported over the past few decades, these machines were developed for performing only specific tasks and the functions imparted to them were limited to a few. Hence, the methodologies for imparting a wide variety of functions to machines have not been fully explored. In this study, a novel construction strategy for the multifunctional micromachines is presented, where a specific function can be added to the machine in one step by directly combining the protein-based component, possessing the biological function of constituent proteins, to an arbitrary position of the machine by using an inkjet printing technique. As a proof-of-concept demonstration, various types of machines were constructed by combining multiple components with different functions. These constructed machines successfully performed functions as diverse as enzyme-powered self-propulsion, collection of target objects, including the bilirubin and living cells, enzyme-mediated conversion of substrate molecules to different ones, magnetic guidance, and release of anti-inflammatory drug diapocynin. The study's progressive approach as well as multifunctional and biocompatible machines composed of proteins will profoundly impact the development of intelligent machines equipped with multiplex sophisticated functionalities.

Molecular Machines and Microrobots: Nanoarchitectonics Developments and On-Water Performances.

This review will focus on micromachines and microrobots, which are objects at the micro-level with similar machine functions, as well as nano-level objects such as molecular machines and nanomachines. The paper will initially review recent examples of molecular machines and microrobots that are not limited to interfaces, noting the diversity of their functions. Next, examples of molecular machines and micromachines/micro-robots functioning at the air-water interface will be discussed. The behaviors of molecular machines are influenced significantly by the specific characteristics of the air-water interface. By placing molecular machines at the air-water interface, the scientific horizon and depth of molecular machine research will increase dramatically. On the other hand, for microrobotics, more practical and advanced systems have been reported, such as the development of microrobots and microswimmers for environmental remediations and biomedical applications. The research currently being conducted on the surface of water may provide significant basic knowledge for future practical uses of molecular machines and microrobots.

Laser Machined Fiber-based Microprobe: Application in Microscale Electroporation.

Microscale electroporation devices are mostly restricted to in vitro experiments (i.e., microchannel and microcapillary). Novel fiber-based microprobes can enable in vivo microscale electroporation and arbitrarily select the cell groups of interest to electroporate. We developed a flexible, fiber-based microscale electroporation device through a thermal drawing process and femtosecond laser micromachining techniques. The fiber consists of four copper electrodes (80 µm), one microfluidic channel (30 µm), and has an overall diameter of 400 µm. The dimensions of the exposed electrodes and channel were customizable through a delicate femtosecond laser setup. The feasibility of the fiber probe was validated through numerical simulations and in vitro experiments. Successful reversible and irreversible microscale electroporation was observed in a 3D collagen scaffold (seeded with U251 human glioma cells) using fluorescent staining. The ablation regions were estimated by performing the covariance error ellipse method and compared with the numerical simulations. The computational and experimental results of the working fiber-based microprobe suggest the feasibility of in vivo microscale electroporation in space-sensitive areas, such as the deep brain.

Feasibility of Optical Bearing Fabrication Using Radiation Pressure.

A three-dimensional (3D) printer was used to create a model device to discuss the reduction in friction generated by rotation and investigate the possibility of friction reduction in microelectromechanical systems (MEMSs) using light as a future technology. Experiments on this model showed that friction could be reduced using the light radiation pressure. In addition, the possibility of reducing the effect of the friction generated during rotation was demonstrated by adding a mechanism to the rotating rotor mechanism that reduces friction based on the radiation pressure. The effectiveness and associated problems of 3D printers as a fabrication technology for MEMSs were explored.

Design of a Novel Medical Acoustic Sensor Based on MEMS Bionic Fish Ear Structure.

High-performance medical acoustic sensors are essential in medical equipment and diagnosis. Commercially available medical acoustic sensors are capacitive and piezoelectric types. When they are used to detect heart sound signals, there is attenuation and distortion due to the sound transmission between different media. This paper proposes a new bionic acoustic sensor based on the fish ear structure. Through theoretical analysis and finite element simulation, the optimal parameters of the sensitive structure are determined. The sensor is fabricated using microelectromechanical systems (MEMS) technology, and is encapsulated in castor oil, which has an acoustic impedance close to the human body. An electroacoustic test platform is built to test the performance of the sensor. The results showed that the MEMS bionic sensor operated with a bandwidth of 20-2k Hz. Its linearity and frequency responses were better than the electret microphone. In addition, the sensor was tested for heart sound collection application to verify its effectiveness. The proposed sensor can be effectively used in clinical auscultation and has a high SNR.

Potential of the Coordinated Actions of Multiple Protein-Based Micromachines for Medical Applications.

Untethered mobile micromachines hold great promise in the development of effective and minimally invasive therapies. Although diverse medical micromachines for specific applications have been developed over the past few decades, the coordinated action of multiple machines with different functions remains largely unexplored. In this study, we created three types of biocompatible micromachines using proteins and demonstrated the potential of their coordinated action for medical applications. As a proof of concept, we demonstrated neural replacement therapy, in which neuroblastomas were killed by using an anticancer prodrug and the first machine that contains enzymes, enabling the conversion of the prodrug into a cytotoxic drug. Subsequently, a second machine composed of extracellular matrix was placed on the dead cancer cells to provide a suitable environment for cell adhesion, on which embryonic stem (ES) cells and stromal cells that promote neural differentiation of stem cells were attached by using third machines capable of delivering cells to target positions with desired patterns. As a result, neuroblastomas were replaced with novel healthy neurons derived from ES cells by teaming multiple protein-based machines. We believe that this work highlights the potential of heterogeneous machine groups for medical treatment and the utility of highly biocompatible and functional micromachines made from proteins, representing an important step forward in building more sophisticated micromachine-based therapies.

3D-Printed Multi-Stimuli-Responsive Mobile Micromachines.

Magnetically actuated and controlled mobile micromachines have the potential to be a key enabler for various wireless lab-on-a-chip manipulations and minimally invasive targeted therapies. However, their embodied, or physical, task execution capabilities that rely on magnetic programming and control alone can curtail their projected performance and functional diversity. Integration of stimuli-responsive materials with mobile magnetic micromachines can enhance their design toolbox, enabling independently controlled new functional capabilities to be defined. To this end, here, we show three-dimensional (3D) printed size-controllable hydrogel magnetic microscrews and microrollers that respond to changes in magnetic fields, temperature, pH, and divalent cations. We show two-way size-controllable microscrews that can reversibly swell and shrink with temperature, pH, and divalent cations for multiple cycles. We present the spatial adaptation of these microrollers for penetration through narrow channels and their potential for controlled occlusion of small capillaries (30 µm diameter). We further demonstrate one-way size-controllable microscrews that can swell with temperature up to 65% of their initial length. These hydrogel microscrews, once swollen, however, can only be degraded enzymatically for removal. Our results can inspire future applications of 3D- and 4D-printed multifunctional mobile microrobots for precisely targeted obstructive interventions (e.g., embolization) and lab- and organ-on-a-chip manipulations.

Wafer-Bonding Fabricated CMUT Device with Parylene Coating.

The advantages of the capacitive micromachined ultrasound transducer (CMUT) technology have provided revolutionary advances in ultrasound imaging. Extensive research on CMUT devices for high-frequency medical imaging applications has been conducted because of strong demands and fabrication realization by using standard silicon IC fabrication technology. However, CMUT devices for low-frequency underwater imaging applications have been rarely researched because it is difficult to fabricate thick membrane structures through depositing processes using standard IC fabrication technology due to stress-related problems. To address this shortcoming, in this paper, a CMUT device with a 2.83-µm thick silicon membrane is proposed and fabricated. The CMUT device is fabricated using silicon fusion wafer-bonding technology. A 5-µm thick Parylene-C is conformally deposited on the device for immersion measurement. The results show that the fabricated CMUT can transmit an ultrasound wave, receive an ultrasound wave, and have pulse-echo measurement capability. The ability of the device to emit and receive ultrasonic waves increases with the bias voltage but does not depend on the voltage polarity. The results demonstrate the viability of the fabricated CMUT in low-frequency applications from the perspectives of the device structure, fabrication, and characterization. This study presents the potential of the CMUT for underwater ultrasound imaging applications.

Controlled Mechanical Motions of Microparticles in Optical Tweezers.

Optical tweezers, formed by a highly focused laser beam, have intriguing applications in biology and physics. Inspired by molecular rotors, numerous optical beams and artificial particles have been proposed to build optical tweezers trapping microparticles, and extensive experiences have been learned towards constructing precise, stable, flexible and controllable micromachines. The mechanism of interaction between particles and localized light fields is quite different for different types of particles, such as metal particles, dielectric particles and Janus particles. In this article, we present a comprehensive overview of the latest development on the fundamental and application of optical trapping. The emphasis is placed on controllable mechanical motions of particles, including rotation, translation and their mutual coupling under the optical forces and torques created by a wide variety of optical tweezers operating on different particles. Finally, we conclude by proposing promising directions for future research.

On-Chip Tunable Cell Rotation Using Acoustically Oscillating Asymmetrical Microstructures.

The precise rotational manipulation of cells and other micrometer-sized biological samples is critical to many applications in biology, medicine, and agriculture. We describe an acoustic-based, on-chip manipulation method that can achieve tunable cell rotation. In an acoustic field formed by the vibration of a piezoelectric transducer, acoustic streaming was generated using a specially designed, oscillating asymmetrical sidewall shape. We also studied the nature of acoustic streaming generation by numerical simulations, and our simulation results matched well with the experimental results. Trapping and rotation of diatom cells and swine oocytes were coupled using oscillating asymmetrical microstructures with different vibration modes. Finally, we investigated the relationship between the driving voltage and the speed of cell rotation, showing that the rotational rate achieved could be as large as approximately 1800 rpm. Using our device, the rotation rate can be effectively tuned on demand for single-cell studies. Our acoustofluidic cell rotation approach is simple, compact, non-contact, and biocompatible, permitting rotation irrespective of the optical, magnetic, or electrical properties of the specimen under investigation.

A Generic Control Architecture for Hybrid Micro-Machines.

Hybrid micro-machining, which integrates several micro-manufacturing processes on one platform, has emerged as a solution to utilize the so-called "1 + 1 = 3" effect to tackle the manufacturing challenges for high value-added 3D micro-products. Hybrid micro-machines tend to integrate multiple functional modules from different vendors for the best value and performance. However, the lack of plug-and-play solutions leads to tremendous difficulty in system integration. This paper proposes a novel three-layer control architecture for the first time for the system integration of hybrid micro-machines. The interaction of hardware is encapsulated into software components, while the data flow among different components is standardized. The proposed control architecture enhances the flexibility of the computer numerical control (CNC) system to accommodate a broad range of functional modules. The component design also improves the scalability and maintainability of the whole system. The effectiveness of the proposed control architecture has been successfully verified through the integration of a six-axis hybrid micro-machine. Thus, it provides invaluable guidelines for the development of next-generation CNC systems for hybrid micro-machines.

The History and Horizons of Microscale Neural Interfaces.

Microscale neural technologies interface with the nervous system to record and stimulate brain tissue with high spatial and temporal resolution. These devices are being developed to understand the mechanisms that govern brain function, plasticity and cognitive learning, treat neurological diseases, or monitor and restore functions over the lifetime of the patient. Despite decades of use in basic research over days to months, and the growing prevalence of neuromodulation therapies, in many cases the lack of knowledge regarding the fundamental mechanisms driving activation has dramatically limited our ability to interpret data or fine-tune design parameters to improve long-term performance. While advances in materials, microfabrication techniques, packaging, and understanding of the nervous system has enabled tremendous innovation in the field of neural engineering, many challenges and opportunities remain at the frontiers of the neural interface in terms of both neurobiology and engineering. In this short-communication, we explore critical needs in the neural engineering field to overcome these challenges. Disentangling the complexities involved in the chronic neural interface problem requires simultaneous proficiency in multiple scientific and engineering disciplines. The critical component of advancing neural interface knowledge is to prepare the next wave of investigators who have simultaneous multi-disciplinary proficiencies with a diverse set of perspectives necessary to solve the chronic neural interface challenge.

Topographical Manipulation of Microparticles and Cells with Acoustic Microstreaming.

Precise and reproducible manipulation of synthetic and biological microscale objects in complex environments is essential for many practical biochip and microfluidic applications. Here, we present an attractive acoustic topographical manipulation (ATM) method to achieve efficient and reproducible manipulation of diverse microscale objects. This new guidance method relies on the acoustically induced localized microstreaming forces generated around microstructures, which are capable of trapping nearby microobjects and manipulating them along a determined trajectory based on local topographic features. This unique phenomenon is investigated by numerical simulations examining the local microstreaming in the presence of microscale boundaries under the standing acoustic wave. This method can be used to manipulate a single microobject around a complex structure as well as collectively manipulate multiple objects moving synchronously along complicated shapes. Furthermore, the ATM can serve for automated maze solving by autonomously manipulating microparticles with diverse geometries and densities, including live cells, through complex maze-like topographical features without external feedback, particle modification, or adjustment of operational parameters.

Newly developing endoscopic devices--shadow optics and micromachine

Based on the newly-developed engineering technologies, many kinds of useful equipment have been available for minimally invasive surgery. Recently the time to connect clinical needs and advanced technologies has become faster. In this article, we have summarized the recent technologies for endoscopic surgeries. Shadow optic technologies for better geometric perception using dual illumination in a conventional 2-D monitor and "Overview optics" for a panoramic view with an additional visual system are introduced. Micromachine technology is very close to practical implementation for minimally invasive surgeries. Virtual Biopsy is the one of the hottest topics for the next generation of endoscopy. Stereoscopic and volumetric vision systems are still on the way, which should overcome the irritating goggles and stereo display devices. As well as operational theater that integrates all the required equipment with a computer-based system, including voice recognition, still requires the standard protocols to connect many kinds of devices from different manufacturers.