Intermediate Pumping Chamber With SMA Actuation for Precise Drug Dosing

The patent replaces the conventional mechanical plunger-based pump mechanism with a shape memory alloy (SMA) wire-driven system. The SMA wire undergoes phase transformation under electrical stimulation to change length, directly actuating the sliding fluidic member without complex mechanical linkages. This substitution eliminates mechanical sticking and slipping issues while maintaining reliable dosing accuracy.

The patent utilizes the phase transformation property of shape memory alloy wire, which changes its length in response to temperature changes induced by electrical current. This parameter change (length contraction upon heating) directly drives the pumping action, providing precise and repeatable motion that eliminates the mechanical inaccuracies of conventional plunger systems.

The patent combines multiple functions into integrated components. The sliding fluidic member integrates the plunger function, valve function, and fluid pathway into a single movable component. The SMA wire directly actuates this integrated member, eliminating the need for separate linkages, springs, and mechanical transmission elements, thereby reducing overall device volume while maintaining reliable drug expulsion.

The patent employs a compact nested arrangement where the sliding fluidic member moves within the pump chamber, and the SMA wire is contained within or alongside these components. The plunger channel and flow orifice are integrated within the sliding fluidic member structure, creating a space-efficient configuration that minimizes device size.

The patent replaces complex mechanical actuation systems with a direct SMA wire actuation mechanism. The phase transformation of the SMA wire provides smooth, controlled motion without the friction, backlash, or mechanical play that cause sticking and slipping in simplified mechanical systems. This maintains dosing precision while achieving device size reduction.

The patent exploits the reversible phase transition of shape memory alloy between austenite (high-temperature, contracted state) and martensite (low-temperature, extended state). This phase transition provides a clean, repeatable actuation cycle without mechanical wear or friction, ensuring dosing precision in a compact device configuration.