A Flexible Microfluidic-Based Sensor for Monitoring the Bending and Tilting of a Metal Bar for Pectus Excavatum (PE) Patients

In this paper, a flexible microfluidic-based sensor is investigated for monitoring the bending and tilting of a metal bar for miniature access pectus excavatum repair (MAPER). Built on a polyethylene terephthalate (PET) substrate, the sensor contains a polydimethylsiloxane (PDMS) microstructure embedded with an electrolyte-enabled 5×1 resistive transducer array. One end of the metal bar is fixed and the sensor is attached to different locations of the bar. The other end of the metal bar is connected to a 5-lb weight for controlling the bending of the bar. Manually holding and releasing the weight bends the metal bar, which translates to strain in the PET substrate and consequently causes resistance changes in the transducer array. Upon the same amount of bending, resistance change of the sensor varies with the location of the sensor on the metal bar, due to the bending (or strain) variation along its length. Tilting of the metal bar relative to a rigid object (i.e., sternum) introduces force acting on the microstructure of the sensor, and thus gives rise to resistance changes in the transducer array. As a result, this sensor shows the potential of being used in MAPER to minimize tissue injury in vivo application.

A Two-Dimensional Microfluidic-Based Tactile Sensor for Tissue Palpation Under the Influence of Misalignment

This paper reports on a proof-of-concept study of applying a two-dimensional (2D) microfluidic-based tactile sensor for tissue palpation under the influence of misalignment. Two unavoidable misalignment issues, uncertainty in contact point and non-ideal normal contact, severely distort the genuine elasticity distribution of a tissue region, yielding false identification of abnormality. The core of the 2D tactile sensor is one whole microstructure embedded with an electrolyte-enabled 2D resistive transducer array underneath. This unique configuration allows the tactile sensor to interact with a tissue region in a continuous manner that mimics manual palpation: the whole microstructure (fingertip) presses a tissue region and the corresponding deflection distribution is captured concurrently by the embedded transducer array (distributed sensors under the skin). This continuous manner tackles the misalignment issues encountered by an individual sensor or a sensor array, in that any misalignment encountered by the 2D sensor is manifested as an increasing trend of the distributed deflection-depth relations along the tilt direction. Tissue phantoms with embedded nodules and extrusions are prepared and are measured using the 2D tactile sensor, validating the capability of the tactile sensor to identify abnormalities in soft tissue under the influence of misalignment.

Performance of a Nozzle Guide Vane in Subsonic and Transonic Regimes Tested in an Annular Sector

The understanding of shock interactions and mixing phenomena is crucial to design and analysis of advanced turbines. A nozzle guide vane (NGV) is experimentally investigated at subsonic and transonic off-design conditions (M2is of 0.6 and 0.95) in an annular sector at the Royal Institute of Technology (KTH). The effect of cooling ejection (3% of main stream mass flow rate) on the downstream flow field is also studied. The airfoil loading is monitored with pneumatic taps. The downstream pressure field is characterized at four different axial locations using a 5-hole probe and a total pressure probe that contains a single piezo-resistive transducer. The probe with a piezo resistive transducer is also used as a virtual 3-hole probe to measure the flow angle. The time-averaged yaw angle measured with the virtual 3-hole probe is in agreement with the 5-hole probe data. At subsonic conditions the wake causes a pressure loss of 7% of the upstream total pressure and covers 25% of the pitch whereas the pressure deficit is doubled in transonic operation. The coolant ejection results in an additional loss of 2% of the upstream total pressure. The flow speed does not have a significant effect on the wake width at 7% Cax. However, the low pressure region has different width at far downstream depending on the flow velocity. The fillet at the hub region has a significant effect on the secondary flow development. The frequency spectrums at the different conditions clearly reveal the shear layers. The results aim to help the characterization of mixing phenomena downstream of the NGV.