Fabricating cost effective, reliable and functional sensors for electronic skins has been a challenging undertaking for the last several decades. Application of such skins include haptic interfaces, robotic manipulation, and physical human-robot interaction. Much of our recent work has focused on producing compliant sensors that can be easily formed around objects to sense normal, tension, or shear forces. Our past designs have involved the use of flexible sensors and interconnects fabricated on Kapton substrates, and piezoresistive inks that are 3D printed using Electro Hydro Dynamic (EHD) jetting onto interdigitated electrode (IDE) structures. However, EHD print heads require a specialized nozzle and the application of a high-voltage electric field; for which, tuning process parameters can be difficult based on the choice of inks and substrates. Therefore, in this paper we explore sensor fabrication techniques using a novel wet lift-off photolithographic technique for patterning the base polymer piezoresistive material, specifically Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) or PEDOT:PSS. Fabricated sensors are electrically and thermally characterized, and temperaturecompensated designs are proposed and validated. Packaging techniques for sensors in polymer encapsulants are proposed and demonstrated to produce a tactile interface device for a robot.
In order to carry out nanomanufacturing tasks, a microrobot requires both high precision and high reliability over prolonged periods of time. Articulated Four-Axis Microrobots (AFAM) have been introduced a decade ago as millimetric microrobots capable of carrying out nanoscale tasks. The original robot design relied on a Micro Electro Mechanical (MEMS) actuator bank positioned onto a Silicon substrate, and an assembled arm mechanically coupled to the actuators through a cable. Movement of two thermal actuator banks positions the AFAM’s end effector in 3-Dimensional space with approximately 75 microns workspace and 50 nm repeatability. However, failure of the AFAM’s cable mechanism was observed after less than 1 million cycles. In this paper, we propose a novel arm mechanism for AFAM that improve its performance. The design presented in this article substitutes the "wire-gluing" cable with an anchored electrostatic actuator, and therefore it simplifies assembly requirements, reduces overall footprint of the microrobot, and achieves higher operating frequency. Simulation results are presented for a rotary electrostatic comb drive as basis for the microrobot arm with overall dimensions of 2 mm × 2 mm. The AFAM arm cantilever is 1 mm long to achieve a workspace of dimension of 75 microns along the vertical axis. Experimental evaluation of the design was accomplished using a prototype fabricated on a silicon on insulator (SOI) wafer processed with the deep reactive ion etching (DRIE) process.
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