Highly elastic conductive polymeric MEMS

Abstract

Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

Length Changes of the Anterolateral Ligament During Passive Knee Motion

“…1,26,38 The feasibility and reliability of the strain gauge have been demonstrated in previous work. 26,38 An interdigital finger electrode structure forms the active layer of the sensor device. Conductivity is achieved by adding 10.6 wt% carbon particles (ENSACO 250 P; TIMCAL Ltd) to the base polymer.…”

A New Approach to Determine Ligament Strain Using Polydimethylsiloxane Strain Gauges: Exemplary Measurements of the Anterolateral Ligament

“…Figure 1 depicts the sensor device. The fab rication process of this MEMS structure was carried out according to Ruhhammer et al [18]. Neukasil RTV-23® (Altropol Kunststoff GmbH, Stockelsdorf, Germany) was used as the base polymer.…”

“…1. Contrary to the fabrication pro cess as described by Ruhhammer et al [18], a mixture of Neukasil RTV-23® and 38.75 wt.% barium titanate (BaTi03) was used for the encapsulation of the conductive electrode structure. The plain base polymer was used as a substrate to detach the conductive structure, thus leaving the electrodes visible from one side of the sensor.…”

Resistive characterization of soft conductive PDMS membranes for sensor applications

“…Electrical conductivity of PDMS can be achieved by adding conductive fillers [5]. Conductive PDMS is used as an active element in sensors, actuators and many other flexible devices [6].…”

“…Most commonly used conductive fillers for the fabrication of conductive PDMS membranes are Carbon Black (CB) particles, silver (Ag) particles and multi-walled carbon nanotubes (MWCNTs) [5,6]. The electromechanical properties of the membranes vary with the type of fillers.…”