One-step Implantation of a 3D Neural Microelectrode Array.

This paper presents a neurosurgical device called NEIT 2 (Nerve Electrode Insertion Tool) to implant a 3D microelectrode array into a peripheral nervous system. Using an elastomer-made nerve holder, the device is able to stable target a flexible nerve, and then safely inserts an electrode array into the fixed nerve. Finally, a nerve containment assembly is made at once. We conducted animal experiments to evaluate the proposed scenario using a 3D printed prototype and commercial microelectrodes. The results show that microelectrodes are successfully implanted into sciatic nerves of rats and neural signals are recorded through the chronically implanted electrodes.

A Pilot Study On The Novel Non-Invasive Nerve-Holder With Negative-Pressure Suctions.

In performing neurosurgical operation on peripheral nervous system, the most important first step is to robustly hold the target nerve, since the nerve-holding stability and reliability significantly affect the result of surgical operation. However it is not straightforward to robustly hold peripheral nerve during the surgical operation, because the peripheral nerve is too flexible and slippery. In this study, we design a novel peripheral nerve-holder that can be used for the neurosurgical operation. Considering the anatomical characteristics of the peripheral nerve that small bundles of nerve fibers (i.e., fascicles) are structured inside the outermost layer of the nerve bundle (i.e., epineurium), we aim to develop a non-clamping and non-invasive type nerve-holder to protect the nerve fibers. For the aim, the negative-pressure suction method is applied to the proposed holder. And, in order to hold the nerve more robustly, micro-bump structure is fabricated on the suction surface contacting with the nerve. This paper introduces the concept, working principle, characteristics, and in-vitro experimental results on feasibility evaluation of the proposed holder.

A 5-D Localization Method for a Magnetically Manipulated Untethered Robot using a 2-D Array of Hall-effect Sensors.

This paper introduces a new five-dimensional localization method for an untethered meso-scale magnetic robot, which is manipulated by a computer-controlled electromagnetic system. The developed magnetic localization setup is a two-dimensional array of mono-axial Hall-effect sensors, which measure the perpendicular magnetic fields at their given positions. We introduce two steps for localizing a magnetic robot more accurately. First, the dipole modeled magnetic field of the electromagnet is subtracted from the measured data in order to determine the robot's magnetic field. Secondly, the subtracted magnetic field is twice differentiated in the perpendicular direction of the array, so that the effect of the electromagnetic field in the localization process is minimized. Five variables regarding the position and orientation of the robot are determined by minimizing the error between the measured magnetic field and the modeled magnetic field in an optimization method. The resulting position error is 2.1±0.8 mm and angular error is 6.7±4.3° within the applicable range (5 cm) of magnetic field sensors at 200 Hz. The proposed localization method would be used for the position feedback control of untethered magnetic devices or robots for medical applications in the future.

Biomedical Applications of Untethered Mobile Milli/Microrobots.

Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biome dical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

Biopsy using a magnetic capsule endoscope carrying, releasing, and retrieving untethered microgrippers.

This paper proposes a new wireless biopsy method where a magnetically actuated untethered soft capsule endoscope carries and releases a large number of thermo-sensitive, untethered microgrippers (µ-grippers) at a desired location inside the stomach and retrieves them after they self-fold and grab tissue samples. We describe the working principles and analytical models for the µ-gripper release and retrieval mechanisms, and evaluate the proposed biopsy method in ex vivo experiments. This hierarchical approach combining the advanced navigation skills of centimeter-scaled untethered magnetic capsule endoscopes with highly parallel, autonomous, submillimeter scale tissue sampling µ-grippers offers a multifunctional strategy for gastrointestinal capsule biopsy.

Magnetically Actuated Soft Capsule With the Multimodal Drug Release Function.

In this paper, we present a magnetically actuated multimodal drug release mechanism using a tetherless soft capsule endoscope for the treatment of gastric disease. Because the designed capsule has a drug chamber between both magnetic heads, if it is compressed by the external magnetic field, the capsule could release a drug in a specific position locally. The capsule is designed to release a drug in two modes according to the situation. In the first mode, a small amount of drug is continuously released by a series of pulse type magnetic field (0.01-0.03 T). The experimental results show that the drug release can be controlled by the frequency of the external magnetic pulse. In the second mode, about 800 mm3 of drug is released by the external magnetic field of 0.07 T, which induces a stronger magnetic attraction than the critical force for capsule's collapsing. As a result, a polymeric coating is formed around the capsule. The coated area is dependent on the drug viscosity. This paper presents simulations and various experiments to evaluate the magnetically actuated multimodal drug release capability. The proposed soft capsules could be used as minimally invasive tetherless medical devices with therapeutic capability for the next generation capsule endoscopy.

3-D Localization Method for a Magnetically Actuated Soft Capsule Endoscope and Its Applications.

In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0-3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis.