Search

Most mobile phones today have capacitive micro-electro-mechanical systems (MEMSs) microphones that use either single or dual diaphragms. Methods to detect failures easily and non-invasively have become of critical importance for microphones mobile phone manufacturers as a basis for built-in self-test (BIST) and self-repair (BISR) strategies. In that regard, a four-layer framework is presented that includes lumped element modeling (LEM), failure mode simulation, failure mode discrimination, and recovery. The frequency response of the microphone is taken as the main output to analyze. To experimentally validate this framework, this article provides a failure mode induction method based on bias voltage sweeping and four new techniques, based solely on acoustic measurements to discriminate the states of electrostatic capture for single diaphragm capacitive MEMS microphones. These include 1) analysis of an acoustic signature that is unique to electrostatic capture based on cosine similarity analysis; 2) −3 dB point measurement; 3) +3 dB point measurement; and 4) cluster analysis. Measurement of pull-in voltage and snapback voltage ranges is further demonstrated based on sensitivity measurements in laboratory conditions and response magnitude and noise power measurements in non-laboratory conditions. Up to 100% success rate in detecting electrostatic capture of diaphragm is reported for this type of device. [ABSTRACT FROM AUTHOR]

Frequency response to stimuli applied to acoustic micro-electro-Mechanical Systems (MEMS) yield meaningful information of certain defects affecting such devices. This article presents the effects of three distinct root causes of failures affecting the low-frequency response of MEMS microphones: lid attach holes, die attach holes and broken vents with experimental inductions of these effects for the lid attach holes and broken vents. Methods to create such defects are presented which include laser drilling and focused ion beam machining of holes. A complete characterization of induced broken vents is presented. Alternative locations for defects induction are proposed and demonstrated on 34 devices, 16 with lid attach holes and 18 with induced broken vents. The information obtained from the frequency response of the devices is shown to be insufficient to separate the root causes of failures as their effects on the frequency response is similar and the magnitudes of the variations of the observed response overlap. Additional information about the circumstances regarding the onset of defects such as location of the fault and its occurrence in the device manufacturing/assembly/operation timeline is however sufficient for root cause identification. [ABSTRACT FROM AUTHOR]

Clinical endoscopy and colonoscopy are commonly used to investigate and diagnose disorders in the upper gastrointestinal tract and colon, respectively. However, examination of the anatomically remote small bowel with conventional endoscopy is challenging. This and advances in miniaturization led to the development of video capsule endoscopy (VCE) to allow small bowel examination in a noninvasive manner. Available since 2001, current capsule endoscopes are limited to viewing the mucosal surface only due to their reliance on optical imaging. To overcome this limitation with submucosal imaging, work is under way to implement microultrasound (μUS) imaging in the same form as VCE devices. This paper describes two prototype capsules, termed Sonocap and Thermocap, which were developed respectively to assess the quality of μUS imaging and the maximum power consumption that can be tolerated for such a system. The capsules were tested in vivo in the oesophagus and small bowel of porcine models. Results are presented in the form of μUS B-scans as well as safe temperature readings observed up to 100 mW in both biological regions. These results demonstrate that acoustic coupling and μUS imaging can be achieved in vivo in the lumen of the bowel and the maximum power consumption that is possible for miniature μUS systems. [ABSTRACT FROM AUTHOR]

Image-guided surgery is today considered to be of significant importance in neurosurgical applications. However, one of its major shortcomings is its reliance on preoperative image data, which does not account for brain deformations and displacements that occur during surgery. In this work, we propose to tackle this issue through the incorporation of an ultrasound device within the type of biopsy needles commonly used as an interventional tool to provide immediate feedback to neurosurgeons during surgical procedures. To identify the most appropriate path to access a targeted tissue site, single-element transducers that look either forward or sideways have been designed and fabricated. Micromolded 1–3 piezocomposites were adopted as the active materials for feasibility tests and epoxy lenses have been applied to focus the ultrasound beam. Electrical impedance analysis, pulse-echo testing, and wire phantom scanning have been carried out, demonstrating the functionality of the needle transducers at \sim16\,\textMHz. The capabilities of these transducers for intraoperative image guidance were demonstrated by imaging within soft-embalmed cadaveric human brain and fresh porcine brain. [ABSTRACT FROM PUBLISHER]