Integration of reconfigurable microchannels into aligned three-dimensional neural networks for spatially controllable neuromodulation.

Anisotropically organized neural networks are indispensable routes for functional connectivity in the brain, which remains largely unknown. While prevailing animal models require additional preparation and stimulation-applying devices and have exhibited limited capabilities regarding localized stimulation, no in vitro platform exists that permits spatiotemporal control of chemo-stimulation in anisotropic three-dimensional (3D) neural networks. We present the integration of microchannels seamlessly into a fibril-aligned 3D scaffold by adapting a single fabrication principle.

Time-Dependent Wetting Scenarios of a Water Droplet on Surface-Energy-Controlled Microcavity Structures with Functional Nanocoatings.

We report the surface-energy-dependent wetting transition characteristics of an evaporating water droplet on surface-energy-controlled microcavity structures with functional nanocoatings. The droplet wetting scenarios were categorized into four types depending on the synergistic effect of surface energy and pattern size. The silicon (Si) microcavity surfaces ( = 69.

MEMS devices for drug delivery.

Novel drug delivery systems based on microtechnology have advanced tremendously, but yet face some technological and societal hurdles to fully achieve their potential. The novel drug delivery systems aim to deliver drugs in a spatiotemporal- and dosage-controlled manner with a goal to address the unmet medical needs from oral delivery and hypodermic injection. The unmet needs include effective delivery of new types of drug candidates that are otherwise insoluble and unstable, targeted delivery to areas protected by barriers (e.

Anisotropically organized three-dimensional culture platform for reconstruction of a hippocampal neural network.

In native tissues, cellular and acellular components are anisotropically organized and often aligned in specific directions, providing structural and mechanical properties for actuating biological functions. Thus, engineering alignment not only allows for emulation of native tissue structures but might also enable implementation of specific functionalities. However, achieving desired alignment is challenging, especially in three-dimensional constructs.

Individual Role of the Physicochemical Characteristics of Nanopatterns on Tribological Surfaces.

Nanoscale patterns have dimensions that are comparable to the length scales affected by intermolecular and surface forces. In this study, we systematically investigated the individual roles of curvature, surface energy, lateral stiffness, material, and pattern density in the adhesion and friction of nanopatterns. We fabricated cylindrical and mushroom-shaped polymer pattern geometries containing flat- and round-topped morphologies using capillary force lithography and nanodrawing techniques.

Nanotribological and wetting performance of hierarchical patterns.

Surface modification is a promising method to solve the tribological problems in microsystems. To modify the surface, we fabricated hierarchical patterns with different pitches of nano-scale features and different surface chemistries. Micro- and nano-patterns with similar geometrical configurations were also fabricated for comparison.

In vivo optical modulation of neural signals using monolithically integrated two-dimensional neural probe arrays.

Integration of stimulation modalities (e.g. electrical, optical, and chemical) on a large array of neural probes can enable an investigation of important underlying mechanisms of brain disorders that is not possible through neural recordings alone.

Role of Viscous Dissipative Processes on the Wetting of Textured Surfaces.

We investigate the role of viscous forces on the wetting of hydrophobic, semi-hydrophobic, and hydrophilic textured surfaces as second-order effects. We show that during the initial contact, the transition from inertia- to viscous-dominant regime occurs regardless of their surface topography and chemistry. Furthermore, we demonstrate the effect of viscosity on the apparent contact angle under quasi-static conditions by modulating the ratio of a water/glycerol mixture and show the effect of viscosity, especially on the semi-hydrophobic and hydrophobic textured substrates.

Neural probes with multi-drug delivery capability.

Multi-functional neural probes are promising platforms to conduct efficient and effective in-depth studies of brain by recording neural signals as well as modulating the signals with various stimuli. Here we present a neural probe with an embedded microfluidic channel (chemtrode) with multi-drug delivery capability suitable for small animal experiments. We integrated a staggered herringbone mixer (SHM) in a 3-inlet microfluidic chip directly into our chemtrode.

The role of bio-inspired hierarchical structures in wetting.

Superhydrophobicity facilitates the development of self-cleaning, anti-biofouling, and anti-corrosion surfaces. The leaves of the lotus (Nelumbo nucifera) and taro (Colocasia esculenta) plants are well known for their self-cleaning properties. A hierarchical structure comprising papillae epidermal cells superimposed with epicuticular wax crystalloids of varying shapes, sizes, and orientations is an important aspect of the surface of these plant leaves.

A multichannel neural probe with embedded microfluidic channels for simultaneous in vivo neural recording and drug delivery.

Multi-functional neural probes integrated with various stimulation modalities are becoming essential tools in neuroscience to study the brain more effectively. In this paper, we present a new multi-functional neural probe that allows chemical stimulation through drug delivery and simultaneous recording of individual neuron signals through a microelectrode array. By embedding microchannels in silicon using a proposed glass reflow process, we successfully fabricated 40 μm thick silicon neural probes suitable for small animal experiments.

Effect of topography on the wetting of nanoscale patterns: experimental and modeling studies.

We investigated the influence of nanoscale pattern shapes, contours, and surface chemistry on wetting behavior using a combination of experimental and modeling approaches. Among the investigated topographical shapes, re-entrant geometries showed superior performance owing to their ability to restrain the liquid-air interface in accordance with Gibbs criteria. The wetting state is also controlled by the surface texture in addition to the surface chemistry.

Nanomechanical measurement of astrocyte stiffness correlated with cytoskeletal maturation.

Astrocytes are known to serve as scaffolding cells that shape the brain. The physical properties of astrocytes, such as stiffness, are important for their scaffolding function. These properties may be altered in certain pathological conditions, such as in brain cancer.

Design of endoscopic micro-robotic end effectors: safety and performance evaluation based on physical intestinal tissue damage characteristics.

During the last several years, legged locomotive mechanism has been considered as one of the main self-propelling mechanisms for future endoscopic microrobots due to its superior propulsion efficiency of an endoscopic microrobot inside the intestinal track. Nevertheless, its clinical application has been largely limited since the legged locomotive mechanism utilizes an end effector which has a sharp tip to generate sufficient traction by physically penetrating and interlocking with the intestinal tissue. This can cause excessive physical tissue damage or even complete perforation of the intestinal wall that can lead to abdominal inflammation.

An implantable neural probe with monolithically integrated dielectric waveguide and recording electrodes for optogenetics applications.

Objective: Optogenetics promises exciting neuroscience research by offering optical stimulation of neurons with unprecedented temporal resolution, cell-type specificity and the ability to excite as well as to silence neurons. This work provides the technical solution to deliver light to local neurons and record neural potentials, facilitating local circuit analysis and bridging the gap between optogenetics and neurophysiology research.

Approach: We have designed and obtained the first in vivo validation of a neural probe with monolithically integrated electrodes and waveguide.

Autonomous locomotion of capsule endoscope in gastrointestinal tract.

Autonomous locomotion in gastrointestinal (GI) tracts is achieved with a paddling-based capsule endoscope. For this, a miniaturized encoder module was developed utilizing a MEMS fabrication technology to monitor the position of paddles. The integrated encoder module yielded the high resolution of 0.

The first neural probe integrated with light source (blue laser diode) for optical stimulation and electrical recording.

In this paper, we report a neural probe which can selectively stimulate target neurons optically through Si wet etched mirror surface and record extracellular neural signals in iridium oxide tetrodes. Consequently, the proposed approach provides to improve directional problem and achieve at least 150/m gap distance between stimulation and recording sites by wet etched mirror surface in V-groove. Also, we developed light source, blue laser diode (OSRAM Blue Laser Diode_PL 450), integration through simple jig for one-touch butt-coupling.

Feedback controlled piezo-motor microdrive for accurate electrode positioning in chronic single unit recording in behaving mice.

The microdrive is one of the most essential tools for extracellular, single-unit recordings in freely behaving animals to detect and isolate the single-unit activities from brain regions of interest. Due to the increasing number of neuroscience research projects using genetically engineered mice, the demand for effective recording devices in freely moving mice is also increasing. Although manually and automatically operated microdrive devices are available, they are limited in terms of size, weight, accuracy, manipulability, and convenience for single-unit recording in mice.

Active locomotion of a paddling-based capsule endoscope in an in vitro and in vivo experiment (with videos).

Background: Capsule endoscopy that could actively move and approach a specific site might be more valuable for the diagnosis or treatment of GI diseases.

Objective: We tested the performance of active locomotion of a novel wired capsule endoscope with a paddling-based locomotion mechanism, using 3 models: a silicone tube, an extracted porcine colon, and a living pig.

Design: In vitro, ex vivo, and in vivo experiments in a pig model.

An optimal micropatterned end-effecter for enhancing frictional force on large intestinal surface.

We present a simple surface modification method for enhancing the frictional properties on soft, viscoelastic tissue of large intestine by integrating micropatterned structures with controlled shape and geometry. The micropatterned end-effecter (EE) was fabricated onto micromachined EE body (20 mm long, 2 mm diameter cylinders) in the forms of line, box, pyramid, and bottle shape by utilizing capillary molding technique with UV-curable poly(urethane acrylate) (PUA) polymer. To evaluate the frictional behavior of micropatterned EE, we employed a biotribotester, for easy loading and test of a biological organ specimen.

An improved measurement of dsDNA elasticity using AFM.

The mechanical properties of a small fragment (30 bp) of an individual double-stranded deoxyribonucleic acid (dsDNA) in water have been investigated by atomic force microscopy (AFM). We have stretched three systems including ssDNA, double-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, this was reversed for the other complementary strand) and single-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, whereas the other complementary strand was biotinylated at only the 5'-end). The achieved thiolation and biotinylation were to bind ds- or ssDNA to the gold surface and streptavidin-coated AFM tip, respectively.

Improvement of locomotive performance of capsular microrobot moving in GI tract using position based feedback control.

The position based feedback control system is proposed in order to improve the locomotive performance of the paddling based capsular microrobot moving in gastrointestinal (GI) tracts. The miniaturized optical encoder is designed and fabricated for the positional feedback of the mobile in the microrobot, which results in the precise positioning with the resolution of 0.1 mm.

Piezo motor based microdrive for neural signal recording.

The miniature piezo motor based microdrive which is applicable to the neural signal recording in mice is presented. The microdrive is manipulated by the micromotion of the mobile coupled to the piezo motor generating the flexural vibration within the range of 3.8 mm, with the resolution of 60nm.

Micro capsule endoscope for gastro intestinal tract.

A novel capsule endoscope (CE) named "MiRo" was developed based on a completely new transmission technology known as "electric-field propagation." This technology marks the initial achievement of cooperative research between the Intelligent Microsystem Center of KIST, IntroMedic Co., Ltd, and Yonsei University College of Medicine under Korea's Frontier 21 project.

Establishment of a fabrication method for a long-term actuated hybrid cell robot.

We developed a novel method to fabricate a crab-like microrobot that can actuate for a long period in a physiological condition. The microrobot backbone was built with a biocompatible and elastic material-polydimethylsiloxane (PDMS)-by using a specially designed 3D molding aligner, and consisted of three strips of PDMS "legs" connected across a "body." Cardiomyocytes were then plated on the grooved top surface of the backbone, resulting in a high concentration of pulsating cells.