Design, simulation, and fabrication of an ingestible capsule with gastric balloon for obesity treatment

The treatment of obesity based only on lifestyle changes has been shown ineffectiveness in a long-term period. The development of more definitive and non-invasive therapies has been the subject of study. In this paper, a magnetically driven ingestible capsule with the capacity to inflate a gastric balloon is devised, simulated, and fabricated. The balloon is inflated to a volume of 150 ml using an acid-base reaction between citric acid and potassium bicarbonate. Finite element method simulations were performed to study the interaction between the permanent external magnet and the ingestible capsule and confirm the magnetic activation mechanism. A fabrication process was proposed to manufacture a polydimethylsiloxane (PDMS) balloon in a simple, functional, and reproducible way. The two layers and 1:8 ratio balloons are the most cost-effective without compromising their mechanical properties. The capsule body parts manufactured by a three-dimensional (3D) printing process - Digital Light Processing (DLP) showed high accuracy and excellent resolution. This study demonstrated that the proposed ingestible capsule would successfully inflate the gastric balloon to treat obesity.

Design and manufacturing challenges of optogenetic neural interfaces: a review

Optogenetics is a relatively new technology to achieve cell-type specific neuromodulation with millisecond-scale temporal precision. Optogenetic tools are being developed to address neuroscience challenges, and to improve the knowledge about brain networks, with the ultimate aim of catalyzing new treatments for brain disorders and diseases. To reach this ambitious goal the implementation of mature and reliable engineered tools is required. The success of optogenetics relies on optical tools that can deliver light into the neural tissue. Objective/Approach: Here, the design and manufacturing approaches available to the scientific community are reviewed, and current challenges to accomplish appropriate scalable, multimodal and wireless optical devices are discussed.

SIGNIFICANCE

Overall, this review aims at presenting a helpful guidance to the engineering and design of optical microsystems for optogenetic applications.

Fluorescence and diffuse reflectance spectroscopy for early cancer detection using a new strategy towards the development of a miniaturized system

This paper describes the design of a miniature, cost-effective spectroscopy system for assessing tissue biochemical and morphological information using a few wavelengths. This instrument will integrate thin-film optical filters and silicon photodiodes, avoiding the use of a spectrograph and optical fibers. The components in the set-up design are described. The feasibility of using only 16 wavelengths to accurately extract tissue properties is confirmed on physical tissue models. Also, the suitable spectral performance of several optical filters for the selection of these wavelengths is demonstrated. The reduced size of this device will make possible its implementation in an endoscopic capsule.

ECG Data-Acquisition and classification system by using wavelet-domain Hidden Markov Models

This article is concerned with the classification of ECG pulses by using state of the art Continuous Density Hidden Markov Models (CDHMM's). The ECG signal is simultaneously observed at three different level of focus by means of the Wavelet Transform (WT). The types of beat being selected are normal (N), premature ventricular contraction (V) which is often precursor of ventricular arrhythmia, two of the most common class of supra-ventricular arrhythmia (S), named atrial fibrillation (AF), atrial flutter (AFL), and normal rhythm (N). Both MLII and V1 derivations are used. Run time classification errors can be detected at the decoding stage if the classification of each derivation is different. These pulses are selected for a posterior physician analysis. Experimental results were obtained in real data from MIT-BIH Arrhythmia Database and also in data acquired from a developed low-cost Data-Acquisition System.

Automatic continuous ECG monitoring system for over-drug detection in Brugada Syndrome

This paper is concerned with the automatic control of drug administration in patients suffering from Brugada Syndrome (BS). Drugs such as flecainide, procainamide, ajmaline and pilsicainide should be administrated under carefully controlled electrocardiogram (ECG) monitoring given that the treatment must be stopped if some ECG disturbing conditions appear. These conditions are, among others the development of premature ventricular contraction (PVC), atrial fibrillation (AF) and the widening of the QRS wave. The proposed system can detect these abnormalities by using a pattern recognition approach based on Hidden Markov Models (HMM) with features extracted from three scales of the Wavelet Transform (WT). Performances higher than 98% were reached regarding the classification of normal and abnormal pulses. The system was trained and tested mainly in data from the standard MIT-BIH arrhythmia database.

FBG in PVC foils for monitoring the knee joint movement during the rehabilitation process

This paper presents a sensing electronic-free wearable solution for monitoring the body kinematics. The measuring of the knee movements, flexion and extension, with the corresponding joint acting as the rotation axis is shown as working principle. The proposed sensing system is based on a single optical Fiber-Bragg Grating (FBG) with a resonance wavelength of 1547.76 nm. The optical fiber with the FBG is placed inside a new polymeric foil composed by three flexible layers which facilitates its placement in the anatomic parts under investigation while maintaining full sensing capabilities. The way the device is placed in the specific body part to be measured enables the clear detection of the movements in respect to the joint. The proposed solution was tested using a prototype that was built to evaluate the device under different condition tests and also to assess the system's consistency. The designed and fabricated system demonstrates clear advantages in medical fields like physical therapy applications as optical fiber is not affected by electromagnetic interference nor does the system needs complex and expensive electronic systems and mechanical parts. Another advantage is the possibility to measure, record and evaluate specific mechanical parameters of the limbs' motion. Patients with bone, muscular and joint related health conditions, as well as athletes, are within the most important end-user applications.

Breast skin-line detection using dynamic programming

In this paper, we present a novel method to extract the breast skin-line based on dynamic programming. Skin-line extraction is an important preprocessing step in CAD systems; however, it is a challenging problem due to the presence of noise, underexposed regions, which results in a low contrast area near the skin-air interface, and artifacts such as labels. Our proposal utilizes the stroma edge to constrain searching for the border. In order to cope with noise, we consider several candidate points for the border interface which are obtained by the Laplace operator applied in pre-defined directions in the mammogram. The breast contour is obtained from the candidate points using a dynamic programming algorithm. This utilizes a criterion of optimality to obtain the optimum contour by minimization of a cost function. The method was evaluated using 82 mammograms whose contour were manually extracted by a radiologist from the mini-MIAS database. The Polyline Distance Measure was evaluated for each contour selected with the proposed method, obtaining a mean error of 2.05 pixels and a standard deviation of 0.80.

Cardiac arrhythmia classification using wavelets and Hidden Markov Models - a comparative approach

This paper reports a comparative study of feature extraction methods regarding cardiac arrhythmia classification, using state of the art Hidden Markov Models. The types of beat being selected are normal (N), premature ventricular contraction (V) which is often precursor of ventricular arrhythmia, two of the most common class of supra-ventricular arrhythmia (S), named atrial fibrillation (AF), atrial flutter (AFL), and normal rhythm (N). The considered feature extraction methods are the standard linear segmentation and wavelet based feature extraction. The followed approach regarding wavelets was to observe simultaneously the signal at different scales, which means with different level of focus. Experimental results are obtained in real data from MIT-BIH Arrhythmia Database and show that wavelet transform outperforms the conventional standard linear segmentation.

Feature selection on movement imagery discrimination and attention detection

Noninvasive brain-computer interfaces (BCI) translate subject's electroencephalogram (EEG) features into device commands. Large feature sets should be down-selected for efficient feature translation. This work proposes two different feature down-selection algorithms for BCI: (a) a sequential forward selection; and (b) an across-group variance. Power rar ratios (PRs) were extracted from the EEG data for movement imagery discrimination. Event-related potentials (ERPs) were employed in the discrimination of cue-evoked responses. While center-out arrows, commonly used in calibration sessions, cued the subjects in the first experiment (for both PR and ERP analyses), less stimulating arrows that were centered in the visual field were employed in the second experiment (for ERP analysis). The proposed algorithms outperformed other three popular feature selection algorithms in movement imagery discrimination. In the first experiment, both algorithms achieved classification errors as low as 12.5% reducing the feature set dimensionality by more than 90%. The classification accuracy of ERPs dropped in the second experiment since centered cues reduced the amplitude of cue-evoked ERPs. The two proposed algorithms effectively reduced feature dimensionality while increasing movement imagery discrimination and detected cue-evoked ERPs that reflect subject attention.

Flexible PDMS -based dry electrodes for electro-optic acquisition of ECG signals in wearable devices

We present a new type of flexible dry copper electrodes based on Polydimethylsiloxane (PDMS) coatings, requiring no electrical contact with the body. Tests were performed in order to evaluate the performance of these types of electrodes using electro-optic techniques, suitable for wearable devices. Conductive and insulated PDMS layers were fabricated through a spin coating process, reaching a thickness of 100µ. These layers were then deposited on top of a flexible copper sheet. In a first set of experiments PDMS-based electrodes were compared with Ag/AgCl pre-gelled electrodes, showing comparable performances and lower noise signals. In order to test the influence of electrode area into signal strength, different sizes were chosen: 10.14 cm(2), 17.55 cm(2), 25.3 cm(2) and 39 cm(2). The results have shown that the signal strength increases with electrode area. We have also tested the influence of PDMS conductivity in signal strength, by adding two types of nickel to the pre-polymer solution. PDMS conductive electrodes have shown slightly better performances, with amplitudes higher than 200mV, which is the maximum value recorded with PDMS insulated electrodes.

Improving alternate flow mixing by obstacles located along a micro-channel

An essential requirement for any practical fully integrated lab-on-a-chip device is the ability to mix two or more fluids thoroughly and efficiently, i.e., in a reasonable amount of time. This paper presents a way to improve mixing in microfluidic systems combining alternate flows with obstacles using passive mixers. Numerical simulations show that the layers of high and low solute concentration, created by the alternate flow, are split into smaller chunks of fluid, due to the obstacles inserted in the mixing channel, increasing the contact area between high and low concentration regions and decreasing the critical mixing length. This improvement can lead to shorter mixing channels and to low-cost mixers fabricated by planar lithographic technology.

A lab-on-a-chip for spectrophotometric analysis of biological fluids

This paper reports a lab-on-a-chip for application in clinical analysis, especially in the spectrophotometric analysis of biological fluids. It is composed of three parts: (1) a microfluidic system die containing the microchannels fabricated using SU-8 techniques; (2) an optical filtering system based on highly selective Fabry-Perot optical resonators using a stack of CMOS process compatible thin-film layers; (3) a detection and readout system fabricated in a CMOS microelectronic process. The system enables low-cost and selective measurement of the concentration of several biomolecules in biological fluids. Operation is based on optical absorption in a well-defined part of the visible spectrum, defined by the reaction of a specific reagent with a specific biomolecule. Signals proportional to the intensity of the light transmitted through the biological fluid are available at the output in the form of bit streams, which allows simple computer interfacing. Moreover, the optical filtering system enables the measurement using white light illumination, thus avoiding the use of a wavelength dependent light source. This characteristic makes the lab-on-a-chip portable and ensures that the analysis can be performed at any location with instantaneous results, without the use of complex and expensive analysis systems. The quantitative measurement of uric acid and total protein in urine is demonstrated.

The effect of the beta-2-adrenergic agonist clenbuterol or implantation with oestradiol plus trenbolone acetate on protein metabolism in wether lambs

The effects of Revalor (trenbolone acetate plus oestradiol) implantation or the inclusion of clenbuterol (a beta-2-adrenergic agonist) in the diet of wether lambs was studied. Using continuous intravenous infusion of [3H]tyrosine the fractional synthetic rate of mixed protein from three separate muscles was measured. Clenbuterol slightly increased growth rate but had a significant (P less than 0.02) effect on food conversion efficiency. The weight and protein content of the longissimus dorsi and vastus lateralis muscles were increased but no such changes were observed for the vastus intermedius. For the longissimus dorsi at least the increase was probably achieved by a reduction in fractional degradation rate of the muscle protein. Revalor significantly increased the growth rate and food conversion efficiency of the animals. This increase was not specific for muscle. Estimated degradation rates of muscle protein were lower in the treated animals. The possible mode of action of these materials was discussed. The results obtained again highlight the importance of protein degradation in controlling growth.