Design and Characterization of a Pneumatic Multichannel Microfluidic Release Control System for Neutrotransmitter–Based Retinal Prostheses

Abstract

Abstract: : Purpose: To design and characterize a multichannel computer–controlled pneumatic puffing system for use with neurotransmitter–based retinal prostheses. Methods: Three subsystems were designed. Nitrogen–driven pneumatic circuits were built from four–channel modules comprized of a pneumatic filter/capacitor, pressure regulator, and four–channel manifold with one electronic solenoid valve per channel. A pneumatic pressure transducer connected to the output of the pressure regulator allowed precise adjustment of ejection pressure. Electronic solenoid valves were controlled via solid–state relays connected to a high–speed complex–programmable logic device (CPLD). Spatial and temporal stimulation patterns were loaded into a dual–port RAM via a USB 2.0 interface. Stimulus movies were played back from RAM via the CPLD. Results: A 32–channel pneumatic control system was built. Minimum puff duration was 20 milliseconds. Typically 20 psi of pressure was required to eject fluorescein from 0.5 micron lumen pipettes. Diffferences in fluorescein release between microfluidic orifices were normalized using look up tables resident within the dual–port RAM. Conclusions: We have designed and built a scalable microfluidic release control system that incorporates software, hardware and pneumatic subsystems. Look–up table linearization of drug release was possible due to the digital control system.

Keywords: neurotransmitters/neurotransmitter systems • retina: neurochemistry • retina: proximal (bipolar, amacrine, and ganglion cells)