Piezo-electrochemical transducer effect (PECT) intercalated graphite micro-electromechanical actuators

The purpose of this research is to investigate the Piezo-Electrochemical Transducer (PECT) effect in intercalated graphite as a possible mechanism of actuation for micro-electromechanical systems (MEMS). Specifically, this dissertation will answer three research questions addressing the essential elements of a MEMS actuator: actuation material effectiveness, suitability of use with conventional processing methods, and the feasibility of integrating this actuator into a conventional MEMS system. The research questions will be answered through a literature review of similar actuation materials and operational theory of the PECT effect, analytical analyses, modeling, and through thorough analysis of experimental results.; This dissertation presents the results of research into the PECT effect in H2SO4-intercalated graphitized carbon fibers, including both electrical and mechanical characteristics of this effect. This research measures and analyzes data of the first in-plane hybrid PECT actuator consisting of a patterned thin-film highly oriented pyrolytic graphite integrated onto a commercially micromachined physical structure. Strain for PECT devices is later compared to strain generated by current MEMS actuation mechanisms.; PECT fibers achieve up to 1.7% strain in unloaded conditions with 1.4 V of applied potential. In contrast, at this same potential, the piezoelectric material polyvinylidene difluoride (PVDF) generates only 0.01% strain and polysilicon thermal expansion between 0.02 and 0.06% strain depending on the thermal conductivity of the particular polysilicon that the actuators are fabricated in. This work concludes that PECT carbon fiber actuators achieve two orders of magnitude better strain than PVDF piezoelectric actuators and polysilicon thermal expansion in the same voltage range of operation. In addition to this highly improved strain, the devices, after an initial peak power consumption of 227 muW, a PECT P-100 carbon fiber can hold at an actuation potential while consuming only 260 nW of power continuously. Compare PECT power dissipation to a typical polysilicon thermal actuator, with a maximum of 0.2% strain at 11.5 V of bias, consuming 54.4 mW of power when continuously actuated. PECT actuators at this time are only characterized with H2SO4 as an intercalant and can operate only at a maximum theoretical frequency of 80 Hz. This work recommends the encapsulation of a graphite actuator within a conductive polymer for use as a commercial actuator, which will make PECT actuators viable in mainstream MEMS applications. Although slow operation and unpractical intercalants are serious drawbacks to PECT actuators, the characteristics of strain and power consumption presented in this dissertation prove that PECT actuators, given some minor modifications, prove to be a competitive alternative to current MEMS actuators.