Thread Based Battery for Low Power E-textile Applications

Textile electronic systems, or e-textiles, are on the rise but their utility is limited by its power demand. Potential applications include point-of-care diagnostic systems that would enable medical monitoring at the site of care. A small, inexpensive, and easy to use battery would enhance the capabilities of e-textile. Here we propose a thread based battery that attempts to satisfy these requirements. The thread based battery uses chemistry similar to an alkaline battery. The fabrication process involves patterning of current collector (silver epoxy or carbon ink) followed by zinc electroplating and manganese dioxide deposition. Thread present in between these two electrodes serves as the salt bridge. Chemicals needed for the redox reaction, e.g. ammonium chloride, can be impregnated in the thread in solid form. Single cell configuration of battery shows 1 V (open circuit) and up to 18 µA current (R=12 kΩ). Multiple cells can be fabricated in series to achieve higher voltage output. The battery could be easily incorporated into textiles by methods such as sewing or knitting

Laser treated hydrophobic paper: An inexpensive microsystems platform

The purpose of research presented in this dissertation is to develop inexpensive processes and applications using ultra-low cost substrate like paper. Intended applications include, but are not limited to, point of care diagnostic assays, micro-robotics, and flexible electronics. The basic process of patterning utilizes change in the surface properties of a hydrophobic area due to laser ablation. Patterns, up to 60 μm, were created reliably, using cheap hydrophobic paper (wax paper, parchment paper etc.) and CO 2 laser. The ablated area is analyzed using SEM and XPS tools to understand change in physical structure and chemical properties. Further, the patterned substrate is used to controllably deposit various substances such as chemicals, magnetic nano-particles, electrically conductive material to impart functionality to paper. Non-aqueous suspensions in hydrocarbon based liquid such as silicone, were also patterned successfully. These functional papers can be used to create for various applications such as mechanical transduction, sensing, and energy storage. Three different devices are presented here, magnetic actuator, paper-battery, and oxygen sensor. All three devices are designed, fabricated, and characterized to demonstrate capability of paper based systems

A ferrofluid-based wireless pressure sensor

This paper presents a wireless pressure sensor design based on magnetic fluid displacement over a planar coil and its corresponding inductance change. The design of the pressure sensor is presented followed by its fabrication and characterization. Experimental results show a good correlation with a nonlinear model relating the applied pressure to the change in coil self-resonant frequency. A prototype sensor (radius = 6 mm, thickness = 2 mm) based on the above principal using an oil-based ferrofluid (50 mu l, ferrite concentration 2%), a polyimide-embedded planar coil (L = 1 mu H), and a 25 mu m thick polyimide membrane shows a sensitivity of 3 KHz mmHg(-1) with a base-line resonant frequency of f(0) = 109 MHz

A batch-fabricated laser-micromachined PDMS actuator with stamped carbon grease electrodes

In this note, we report on the development of a batch-fabricated laser-micromachined elastomeric cantilever actuator composed of a polydimethylsiloxane (PDMS) bilayer (active/inactive) and soft-lithographically patterned conductive carbon grease electrodes. The described unimorph structure has a low actuation voltage and large out-of-plane displacement. For a 4 mm long, 1 mm wide, and 80 mu m thick actuator, an out-of-plane displacement of 1.2 mm and a maximum force of 25 mu N were measured using 450 V actuation voltage

Waterproof Active Paper via Laser Surface Micropatterning of Magnetic Nanoparticles

Paper is one of the oldest and most abundant materials known to man. Recently, there has been a considerable interest in creating paper devices by combining paper with other functional materials. In this letter, we demonstrate a simple fabrication technique to create water-resistant ferro-patterns on wax paper using CO2 laser ablation. A resolution of about 100 mu m is achieved which is mostly limited by the cellulose fiber size (similar to 50 mu m) in the wax paper and can be improved by using a smaller cellulose matrix. Laser ablation results in modification of surface morphology and chemistry, leading to a change in surface energy. We also present a 2D model for ferrofluid deposition relating the size of the pattern to the amount of ferroparticles deposited on the surface. Finally, a paper gripper is presented to demonstrate advantages of our technique, which allows microscale patterning and machining in a single step

Ferrofluid-Impregnated Paper Actuators

In this paper, we report on an inexpensive method of fabricating miniature magnetic actuators using ferrofluid-impregnated paper. Different types of papers (including soft tissue paper, cleanroom paper, Whatman-1 filter paper, printer paper, and newspaper) were loaded with oil-based ferrofluid, micromachined by a CO(2) laser and coated with a thin layer of parylene-C. The soaking capability of the different papers was investigated, with the soft tissue paper having the highest loading capacity, being able to absorb ferrofluid by as much as six times its original weight. Cantilever actuators fabricated from cleanroom and filter papers were able to generate the largest force (\u3e 40-mg equivalent force), whereas the soft-tissue-paper cantilevers provided the greatest deflection (40 degrees tip angle)

A Batch-Fabricated Single-Layer Elastomeric Actuator With Corrugated Surface

In this paper, we report on the first laser-micromachined batch-fabricated single-layer elastomeric actuator with a corrugated surface profile. The structural material of the cantilever actuator is a single [polydimethylsiloxane (PDMS)] layer, and electrodes are soft lithographically patterned conductive carbon grease. The asymmetric corrugated surface provides a bending moment in a single PDMS layer without the need for a second inactive layer. An actuator which is 5 mm long, 1 mm wide, and 80 mu m thick can generate up to 2-mm out-of-plane displacement with zero applied force and 15 mu N at zero deflection while consuming 20 mu W of static power when actuated with 500 V

A thermophone on porous polymeric substrate

In this Letter, we present a simple, low-temperature method for fabricating a wide-band (\u3e80 kHz) thermo-acoustic sound generator on a porous polymeric substrate. We were able to achieve up to 80 dB of sound pressure level with an input power of 0.511 W. No significant surface temperature increase was observed in the device even at an input power level of 2.5 W. Wide-band ultrasonic performance, simplicity of structure, and scalability of the fabrication process make this device suitable for many ranging and imaging applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737005

Laser-treated hydrophobic paper: an inexpensive microfluidic platform

We report a method for fabricating inexpensive microfluidic platforms on paper using laser treatment. Any paper with a hydrophobic surface coating (e. g., parchment paper, wax paper, palette paper) can be used for this purpose. We were able to selectively modify the surface structure and property (hydrophobic to hydrophilic) of several such papers using a CO(2) laser. We created patterns down to a minimum feature size of 62 +/- 1 mu m. The modified surface exhibited a highly porous structure which helped to trap/localize chemical and biological aqueous reagents for analysis. The treated surfaces were stable over time and were used to self-assemble arrays of aqueous droplets. Furthermore, we selectively deposited silica microparticles on patterned areas to allow lateral diffusion from one end of a channel to the other. Finally, we demonstrated the applicability of this platform to perform chemical reactions using luminol-based hemoglobin detection

An Ocular Tack for Minimally Invasive Continuous Wireless Monitoring of Intraocular Pressure

This paper presents a novel minimally invasive implantable pressure sensing transponder for continuous wireless monitoring of intraocular pressure (IOP). The transponder was designed to make the implantation and retrieval surgery simple while still measuring the true IOP through direct hydraulic contact with the intra-ocular space. Most parts of the sensor sit externally on the sclera and only a micro-needle penetrates inside the vitreous space through pars plana. In vitro tests showed a sensitivity of 15 kHz/mmHg with about 1 mmHg resolution. In vivo tests included one month implantation in rabbits, confirming the device biocompatibility and functionality