Amir Jahanshahi

Stretchable Circuits with Horseshoe Shaped Conductors Embedded in Elastic Polymers

Conformable electronics, i.e., electronics that can be applied on curved surfaces, is demanded nowadays in place of conventional rigid printed circuit board (PCB) based electronics for a number of applications. In the field of stretchable electronics there has been a swift progress in recent years. In this paper we are presenting our contribution to this ever growing topic, including thin-film based polyimide (PI), supported Au stretchable meanders as well as PCB based Cu meanders. These meanders are supported by PI or poly(ethylene naphthalate)/poly(ethylene terephthalate) (PEN/PET) films. Thin-film based stretchable interconnects is targeting mainly the biocompatible environments with demands for strong miniaturization while the PCB based technology is used more for large area applications. Both approaches are reviewed in this paper in terms of fabrication processes, materials and cyclic fatigue reliability. For each technology fabricated demonstrators are presented as well.

PDMS Selective Bonding for the Fabrication of Biocompatible All Polymer NC Microvalves

Microvalves are commonly used in microfluidic systems to control precisely the liquid flow. In this paper, the design and fabrication of a normally-closed (NC) all-polymer membrane-type microvalve is described. The microvalve with a diameter and thickness of 5 mm and 3 mm, respectively, is fabricated completely in biocompatible polydimethylsiloxane (PDMS). The opening pressure, which depends on the adhesion between the membrane and the slab, is reduced to the noticeably low value of 3.4 kPa by the surface oxidation of the PDMS layers. This technique in combination with a selective bonding by Polyethylene terephthalate (PET) shadow masking allows for the fabrication of a high reverse pressure microvalve (no flow up to 0.6 MPa reverse pressure). Other major fabrication steps include PDMS doctor-blading and soft lithography in order to fabricate the thin and surface patterned membranes, respectively. The presented microvalve features a minimum flow rate of 1.0 ml min-1.

Stretchable biocompatible electronics by embedding electrical circuitry in biocompatible elastomers

Stretchable and curvilinear electronics has been used recently for the fabrication of micro systems interacting with the human body. The applications range from different kinds of implantable sensors inside the body to conformable electrodes and artificial skins. One of the key parameters in biocompatible stretchable electronics is the fabrication of reliable electrical interconnects. Although very recent literature has reported on the reliability of stretchable interconnects by cyclic loading, work still needs to be done on the integration of electrical circuitry composed of rigid components and stretchable interconnects in a biological environment. In this work, the feasibility of a developed technology to fabricate simple electrical circuits with meander shaped stretchable interconnects is presented. Stretchable interconnects are 200nm thin Au layer supported with polyimide (PI). A stretchable array of light emitting diodes (LEDs) is embedded in biocompatible elastomer using this technology platform and it features a 50% total elongation.

Fabrication of an implantable stretchable electro-osmosis pump

The aim of this paper is to demonstrate the feasibility of an implantable, low voltage driven microfluidic pump to deliver drugs. The micro pump has a high degree of biocompatibility and mechanical deformation capability, thanks to the use of elastic silicone elastomers (PDMS) for integration and embedding of the pump. We are using the new method of transverse DC electro-osmosis, which is demonstrated already in the literature. The method uses the fabrication of periodic grooves on top of the micro channel and the application of a DC voltage across the channel. In this contribution, for the first time the production and operation of soft elastic versions of such a pump, compatible with body tissue, is demonstrated. For the interconnects, gold is selectively electro-deposited on Cu-foil and is transferred to PDMS layer. Having only gold as the interconnect ascertains the high degree of bio-compatibility of the device. This pump works with voltages about 10V and produces mean flow speeds of about 60μm/s. The flow has also a helical profile which is a very good advantage to use this pump as a mixer for micro fluidic applications. Flow rate is measured by introducing dyed micro particles along with the liquid inside the channel.