Can the Intestine Perform Some Functions of the Kidney?

The majority of patients in countries like India and Pakistan with end-stage renal disease (ESRD) die without renal replacement therapy due to lack of adequate resources. The use of the intestinal mucosa as a semipermeable membrane for removal of urea and creatinine from the body has been previously studied using various types of intestinal lavage for gut dialysis. This study was undertaken in an animal model to assess the applicability, cost of therapy, and acceptability of the method for potential application in humans. Renal failure was induced in six dogs by bilateral ureteric ligation along with six healthy controls. Dialysis fluid was introduced per rectum as an enema, which was repeatedly administered. Clearances of serum creatinine and urea were assessed. Mean recovery of creatinine and urea in dialysate in the present study was around 8.925 mmol/l and around 207.74 μmol//l, respectively. The mean clearances of serum creatinine and urea were, respectively, 0.0683 and 0.0633 ml/sec. Enteral dialysis was effective and, considering its minimal cost (monthly cost will be around US$35–40) vis a vis available methods, it holds promise for the treatment of patients with ESRD. The creation of an appendicostomy for repeated introduction of antegrade enemas would be a consideration

Fabrication of SU-8 Polymer Waveguides Using Focused Ion Beam Lithography

An attempt is made to fabricate air-cladded SU-8 waveguides of different widths on an oxidized Si substrate using focused ion beam lithography with varying ion doses;and this report discusses limitations & advantages of applying the method on SU-8 for waveguide fabrication purpose. Our starting material is Si (100) substrate.The sample is cleaned by Piranha cleaning;H2O2 is poured in a quartz beaker & conc. H2SO4 is slowly dropped into it (volume ratio of the mixture is 1:1),and left undisturbed for 25mins.Next it is thoroughly rinsed with DI water & is blown with dry nitrogen & is put in oxidation furnace.After reaching a temperature of 10500C,it is oxidized in a sequence of dry-wet-dry for 30mins-2hrs-30mins respectively to obtain an oxide thickness of 1µm,which is uniform throughout the wafer surface.Next it has undergone a general heating for 30mins at 1500C.Oxygen Plasma treatment is carried out at a power of 40W for 45secs.It is then spin coated with SU-8 5 polymer at 500rpm for 10secs and ramped to 6000rpm for next 20secs to achieve a resist thickness of ~1.5μm (measured by Dektak surface profiler).It is then baked on a hotplate at 650C and 950C for 1min and 3mins respectively,and cooled at room temperature for 10mins for thermal relaxation.It is then placed on Au coater to obtain a layer of gold before proceeding to FIB lithography for pattern generation. The width of the waveguides as inspected under FESEM is 0.6,0.8,1.0,1.5 and 2.0μm.The depth as obtained from AFM for 1,15&40 doses is 0.195,0.34&0.57μm respectively.The rms roughness values are 0.118,0.415&0.512μm for 1,15&40 doses respectively.However,to operate in single-mode region,waveguide should have film thickness within 0.43&1.72μm as obtained from our indigenously developed modeling software EIMM©.Thus we have chosen 0.57μm etch depth which is obtained on applying dose 40 for trial purpose.However,as thickness is near the cut-off region,it is obvious there will be error & will prone to huge loss;also as dose increases,the milling depth increases,thereby making the surface rougher;and rougher means more prone to optical loss.FIB lithography has also a limitation of scanning long distances.As the current is low here it takes a lot of time to scan the whole waveguide length.We know that for optical characterization,the waveguides should be fabricated edge to edge of the substrate.So our sample is cleaved in such a way that it can be scanned within feasible time.Beam current is kept fixed at 10nA & area dose is 0.01C/cm2.It is observed from SEM view of waveguide edge (where dose for FIB lithography is taken 15) that the portion of the wafer where there is no SU-8 coating on it,the waveguide pattern is fair,thus we can say FIB lithography is favorable on Si rather than SU-8 for higher doses.But FIB has been successfully applied to make any micro-changes in the waveguide structures generated by optical lithography,& creating photonic-crystal waveguide structures made of SU-8 polymer

Focused ion beam fabrication of SU-8 waveguide structures on oxidized silicon

This work deals with SU-8 waveguides and waveguide structures fabricated on an oxidized silicon substrate using ‘Focused ion beam (FIB) lithography’. From our experimentation it seems that FIB method is practically not suitable for fabricating long SU-8 waveguide structures, rather it is more suitable for nanoscale modification of already fabricated waveguides, such as, to fabricate photonic crystal structures

Design of a Novel Polarization-Independent Power Splitter Using Coupled Silicon Rib Waveguides

Design of a three-coupled silicon rib waveguide based polarization-independent power splitter is presented taking into account excess loss in coupled region and total bending loss for double arc S-bends at the output

Micro Ring Resonator Using SU-8 Waveguides for Temperature Sensor

Micro-ring resonator is designed and developed using SU-8 wire waveguides. The design is accomplished using effective-index-based-matrix-method. Device fabrication is done by direct laser writing technique and can be used as a temperature sensor

Design and Analysis of Directional Coupler made of Straight and Curved Silicon Wire Waveguides

Optical directional couplers made of straight and curved silicon wire waveguides are designed and analyzed using effective-index based matrix method. The results will be useful to design microring resonator based optical integrated circuits

Effective indexbased matrix method for silicon waveguides in SOI platform

The work makes an attempt to design and analyze silicon waveguides in silicon on insulator (SOI) platform with the aid of effective index-based matrix method (EIMM). Effective index method is used for wave confinement in depth direction of the waveguides, thus effective indices of the guided modes are computed. A transfer matrix method is applied on the resulted one-dimensional lateral index profile to compute the guided mode propagation constants. Both wire and rib waveguides are designed from its fabrication parameters for single-mode wave propagation at a transmitting wavelength of 1.55 μm. Bending losses of bent wires are estimated by a suitable conformal transformation along with EIMM. From our computed results, it is seen that the bending radii exceeding 1 μm have negligibly small bending losses. The mode profiles of the silicon wires within the waveguides are also computed for both transverse electric (TE) and transverse magnetic (TM) polarizations. Analysis of some special structures, such as wire waveguide with slanted etched walls, and directional coupler made up of straight and/or curved coupled waveguides are also presented. Some of the computed results of this semi-analytical EIMM are validated with commercially available 2D-FDTD method

Design and Fabrication of SU-8 Polymer Based Photonic Crystal Waveguide

We make use of optical lithography along with focused ion beam milling to fabricate our designed photonic crystal waveguide; milling depth of 220nm is obtained with an ion dose of 10K, rms roughness being 33.1nm

Photonic Waveguide Components on Silicon Substrate: Modeling and Experiments

This book focuses on the design and development of SU-8 polymer and silicon waveguide-based devices using the effective index based matrix method. Various fabrication techniques like laser direct writing (LDW), Focused Ion Beam (FIB) and optical lithography are discussed. FIB lithography has been explored for photonic-crystal structures on the waveguide and for directional coupler in coupled region. This technique is shown to be suitable in fabricating photonic crystal structures as well as for making any precise modifications in micro- and nano-meter photonic waveguide structures. This book can be a useful reference for students, researchers, and fabrication engineers working in the areas of integrated optics, optical communications, laser technology and optical lithography for device manufacturing

Design of a Polarization Independent Power Splitter in SOI Platform by Effective Index Based Matrix Method

A compact three-waveguide polarization independent power splitter is designed and analyzed using effective index based matrix method (EIMM) in SOI platform. The device becomes polarization independent for a coupling length of 2.12μm with an excess loss of 0.44 dB at a transmitting wavelength of 1.55μm