Progress Towards an Automatic, Microfabricated Polymer Air-Fluid Sampling Inlet

摘要

The primary objective of this study is to develop a miniature autonomous aerosol-to-fluid sampling inlet as the input to a chemical or biological agent detection system. The principal challenge is creation of a pump capable of generating the required flow of air into a liquid phase (>0.1 cu cm/min), given the constraints of size (<2.5 cu cm), back pressure to inject the aerosol into the liquid phase (40 kPa) and available electrical power. The Phase I goal is to demonstrate the feasibility of employing conducting polymer actuators in this application. Our report, to our knowledge, is the first extensive experimental measurements delineating the relationship between stress, strain, frequency bandwidth, lifetime and energy consumption achievable with conducting polymers. Conducting polypyrrole actuators meet the air sampler pump requirements, notably demonstrating high stresses (5 MPa, 10 x mammalian muscle and the highest reported yet for conducting polymer actuators), and mechanical displacement bandwidths exceeding 10 Hz. Furthermore, while actuators have heretofore depended upon a liquid electrolyte for operation, we demonstrate here the operation of an electrically-activated conducting polymer bilayer actuator independent of a liquid electrolyte (i.e. in air). Our pump design analysis reveals that displacement pumps prove more effective than inertial mechanisms (due to the low Reynolds number regime) for injecting air into a fluid carrier stream. Accordingly, we built and tested both a peristaltic and two versions of a bellows pumps actuated by nickel titanium shape memory alloy fibers and demonstrated pumping speeds two orders of magnitude greater than targeted (>10 cu cm min). Our actuator analysis showed that shape memory alloys have similar contractile characteristics to conducting polymers except for a lower electromechanical efficiency.