SMA Actuator Latch Assembly for Precise Membrane Valve Dispensing
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Solution Overview
Problem
Existing fluidic systems with membrane valves in fluidic cartridges face challenges in achieving precise and accurate dispensing of small volumes of fluids while maintaining a minimal footprint, leading to increased dead volume and cycle times.
Innovation Solution
The implementation of shape memory alloy (SMA) actuators with a latch assembly that allows SMA wires to cool and relax, enabling faster actuation of membrane valves by holding the plunger in the retracted position without continuous energization, thus reducing opposition force and extending the useful life of SMA wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous voltage is applied to SMA wires to maintain actuator rod position, then positioning accuracy is improved, but energy consumption increases and SMA wire lifespan decreases
Solution Approach 1:
The latch assembly is engaged at the end of the actuation stroke to maintain the actuator rod position without continuous voltage application. The SMA wire is energized periodically only when position changes are needed, rather than continuously, thereby reducing energy consumption while maintaining positioning accuracy through the mechanical latch mechanism.
Solution Approach 2:
The latch assembly provides self-holding capability once the actuator rod reaches the desired position. The mechanical latch structure maintains the position autonomously without requiring continuous energy input from the SMA wire, allowing the system to 'serve itself' in maintaining position while consuming minimal energy.
2Measurement precision
If continuous voltage is applied to SMA wires to maintain actuator rod position, then positioning accuracy is improved, but SMA wire lifespan decreases
Solution Approach 1:
The latch assembly enables intermittent operation of the SMA wire by maintaining position mechanically after the wire is de-energized. This periodic energization rather than continuous operation reduces thermal cycling and stress on the SMA wire, thereby extending its operational lifespan while maintaining positioning accuracy.
Solution Approach 2:
The latch assembly takes over the position-maintaining function once engaged, allowing the SMA wire to rest and cool down. This self-holding mechanism reduces the workload and thermal stress on the SMA wire, enabling it to operate within safer temperature and stress limits that extend its service life.
3Area of stationary object
If minimal footprint is maintained in fluidic system design, then device compactness is improved, but dead volume increases
Solution Approach 1:
The actuation system is divided into modular components including the latch assembly, SMA wire, and actuator rod that can be independently optimized. This segmentation allows for compact arrangement of components to minimize footprint while designing fluidic channels with appropriate dimensions to maintain acceptable dead volume levels through careful spatial planning.
Solution Approach 2:
The system transitions from two-dimensional planar layout considerations to three-dimensional spatial optimization. By utilizing vertical space and multi-layer routing of fluidic channels, the design achieves compact footprint while maintaining adequate channel dimensions to minimize dead volume through efficient use of available three-dimensional space.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise and efficient dispensing of small fluid volumes with reduced dead volume and cycle times, minimizing consumable usage and extending the lifespan of SMA actuators.
Implementation Method 1
Applying a voltage to the shape memory alloy wire retracts the shape memory alloy wire
Implementation Method 2
shape memory alloy actuator has a pair of wire mounts, an actuator rod, and a shape memory alloy wire
Data Source
AI summary
Actuation systems and methods are disclosed. An apparatus includes a housing, a printed circuit board, and a plurality of shape memory alloy actuators. The printed circuit board is coupled to the housing. Each shape memory alloy actuator has a pair of wire mounts, an actuator rod, a shape memory alloy wire, and a latch assembly. The pair of wire mounts are coupled to opposing sides of the printed circuit board and the actuator rod has a wire guide. The shape memory alloy wire is coupled to the wire mounts and positioned around the wire guide. The latch assembly is coupled to the printed circuit board. Applying a voltage to the shape memory alloy wire retracts the shape memory alloy wire and causes the corresponding actuator rod to move between a first position and a second position. The latch assembly is to hold the actuator rods in the second position.