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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. However, actual stiffness of astrocytes is not yet well understood. Here, we report that the astrocyte stiffness is positively correlated with the density of cytoskeletal proteins, such as actin filaments, microtubules, and intermediate filaments. The value of the stiffness of astrocytes as measured by atomic force microscopy (AFM) increases 38-fold in five-week-old rats compared to postnatal-day zero pups. Using multicolor confocal microscopy, we found that the complexity of cytoskeletal proteins, such as actin filaments, microtubules, and intermediate filaments, increase as the animal gets older. Our findings indicate that the change of stiffness positively correlates with the maturation of cytoskeletal proteins, and suggest that AFM can be useful as an analytical and diagnostic tool for neuroscience. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 365-370, 2015. [ABSTRACT FROM AUTHOR]

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 0.0025 mm in the linear motion of the paddles. In addition, a PID control method was implemented on a DSP to control the stroke of the paddles accurately. As a result, the average accuracy and the standard deviation were measured to be 0.037 mm and 0.025 mm by a laser position sensor for the repetitive measurements. The locomotive performance was evaluated via ex-vivo tests according to various strokes in paddling. In an in-vivo experiment with a living pig, the locomotion speed was improved by 58% compared with the previous control method relying on a given timer value for reciprocation of the paddles. Finally, the integrated encoder module and the control system allow consistent paddling during locomotion even under loads in GI tract. It provides the autonomous locomotion without intervention in monitoring and controlling the capsule endoscope.

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. Furthermore, optical power and impedance of iridium oxide tetrodes were measured as 200 μW on 5 mW from LD and 206.5 k Ω at 1 kHz and we demonstrated insertion test of probe in 0.5% agarose-gel successfully. We have successfully transmitted a light of 450 nm to optical fiber through the integrated LD using by butt-coupling method.

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. Moreover, the stroke of the mobile is optimized to increase the forwarding velocity of the microrobot. The control performance is verified by comparing the targeted displacement with the measured one under various loading conditions. The velocity of the microrobot is evaluated according to the various strokes and driving voltages under visco-elastically deformable and rare deformable conditions. The control system works properly with high resolution and accuracy and the velocity of the microrobot is maximized under the optimized stroke. In the in-vitro test, the velocity of the microrobot controlled by the position based feedback is increased by 73% when the optimized stroke is applied, compared with the velocity by the time based control.

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. Advancement of electrodes in a mouse brain is monitored by an integrated MR (Magneto-Resistive) sensor. This microdrive has the length of 6.5mm, the width of 6.5 mm, the height of 12 mm and the total weight of 1.63 g only, including PCB for neural signal recording. The displacement of the microelectrode was evaluated and verified as applying the inputs with 5 to 100 pulses, 30 times to the piezo motor according to various driving voltages. The neural signals from the single thalamic neurons in an awake and freely moving mouse were recorded successfully with the presented microdrive.

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. The specifications of "MiRo" include real-time image receiving, 10.8 x 24 mm, 3.3 g, 320 x 320 pixel formats, 3 frame/sec, and over 11 hours of battery time.