BackgroundElectromyography and acceleromyography are common neuromuscular monitoring devices. However, questions still remain regarding the use of acceleromyography in children. This study compared the calibration success rates and intubation conditions in children after obtaining the maximal blockade depending on each of the devicesMethodsChildren, 3 to 6 years old, were randomly allocated to the TOF-Watch SX acceleromyography group or the NMT electromyography group. The induction was performed with propofol, fentanyl, and rocuronium. The bispectral index and 1 Hz single twitch were monitored during observation. The calibration of the each device was begun when the BIS dropped to 60. After successful calibration, rocuronium 0.6 mg/kg was injected. A tracheal intubation was performed when the twitch height suppressed to 0. The rocuronium onset time (time from administration to the maximal depression of twitch height) and intubating conditions were rated in a blinded manner.ResultsThere was no difference in the calibration success rates between the two groups; and the calibration time in the electromyography group (16.7 ± 11.0 seconds) was shorter than the acceleromyography group (28.1 ± 13.4 seconds, P = 0.012). The rocuronium onset time of the electromyography group (73.6 ± 18.9 seconds) was longer than the acceleromyography group (63.9 ± 18.8 seconds, P = 0.042) and the intubation condition of the electromyography group (2.27 ± 0.65) was better than the acceleromyography group (1.86 ± 0.50, P = 0.007).ConclusionsElectromyography offers a better compromise than acceleromyography with respect to the duration of calibration process and surrogate for the optimal time of tracheal intubation in children.

Typical pneumatic soft micro actuators can be manufactured without using heavy driving components such as pumps and power supplies by adopting an independent battery-powered mechanism. In this study, a thermopneumatically operated soft micro bellows actuator was manufactured, and the standalone operation of the actuator was experimentally validated. Thermopneumatic actuation is based on heating a sealed cavity inside the elastomer of the actuator to raise the pressure, leading to deflection of the elastomer. The bellows actuator was fabricated by casting polydimethylsiloxane (PDMS) using the 3D-printed soluble mold technique to prevent leakage, which is inherent in conventional soft lithography due to the bonding of individual layers. The heater, manufactured separately using winding copper wire, was inserted into the cavity of the bellows actuator, which together formed the thermopneumatic actuator. The 3D coil heater and bellows allowed immediate heat transfer and free movement in the intended direction, which is unachievable for conventional microfabrication. The fabricated actuator produced a stroke of 2184 μm, equivalent to 62% of the body, and exerted a force of 90.2 mN at a voltage of 0.55 V. A system in which the thermopneumatic actuator was driven by alkaline batteries and a control circuit also demonstrated a repetitive standalone operation.

A microfluidic chip, in which both the coil heater and the fluidic channel are designed in a three-dimensional iterative structure, is developed and experimentally demonstrated. Using the empty surrounding 3D space, the microfluidic chip increases the heat transfer area, thereby increasing the fluid temperature by 51.3%, with the same power consumption, compared to heaters and channels typically designed on a 2D plane. After casting polydimethylsiloxane (PDMS) into a sacrificial mold printed using a 3D printer and dissolving the mold, the 3D coil Joule heater is fabricated by filling the interior part of the coil with liquid gallium by vacuuming. By adding an insulation wall filled with air having low thermal conductivity, an additional heating of 8.7% is achieved; this demonstrates the advantage of the 3D-printed soluble-mold technique, which can allow faster prototyping than the typical microfabrication based on soft lithography. Thus, this technique enables convenient design modifications with high priority for performance improvement. As all the components are manufactured simultaneously within a biocompatible, single PDMS body (because of the absence of bonding process between the devices), the risk of leakage in the device is inherently avoided, and the device can be bent without causing any fracture. Therefore, the reported fabrication process and devices are expected to contribute to miniaturization and performance enhancement of microfluidics; this will lead to the development of wearable 3D lab-on-a-chip devices in future.

A micro, soft bellow actuator, which is fabricated using a biocompatible material (polydimethylsiloxane (PDMS)) and operates in a pneumatic manner that is harmless to the living body, has been experimentally validated using 3D-printed soluble molds and supports. Typical planar microfabrication techniques for flexible pneumatic actuators with complex geometries generally have inherent design limitations owing to the manner in which 2D thin films are stacked and require multiple lithographic and alignment steps. In this study, micro bellow actuators with 3D structures that cannot be fabricated using the existing softlithography techniques were designed by simulating the mechanical behavior of the actuator based on the nonlinear elastic properties of PDMS. The subsequently designed 3D-printed soluble-mold technique was used to fabricate the bellow actuators with a 10 µm resolution, while taking into consideration the printing quality, which depends on the printing direction and layer thickness of the 3D printer. On evaluating the operating performance, the micro bellow actuator showed a displacement of 1540 µm at the applied pneumatic pressure of 60 kPa and can apply a force of 0.14 N. Even after 10 000 repetitive operations, the change in the operating characteristic was less than 0.44%. It was also demonstrated that fast prototyping of actuators within 48 h is possible without any process revision, even with variable design changes or other soft polymer materials. The reported fabrication technique is a superior approach for fabricating 3D, sealed, soft pneumatic actuators for micro, soft robot applications.

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