A Nonvolatile Switchable-polarity EPM Valve

Abstract

Scalable control of pneumatic and fluidic networks remains fundamentally constrained by architectures that require continuous power input, dense external control hardware, and fixed routing topologies. Current valve arrays rely on such continuous actuation and mechanically fixed routing, imposing substantial thermal and architectural overhead. Here, we introduce the Switchable-polarity ElectroPermanent Magnet (S-EPM), a fundamentally new bistable magnetic architecture that deterministically reverses its external magnetic polarity through transient electrical excitation. By reconfiguring internal flux pathways within a composite magnet assembly, the S-EPM establishes two stable, opposing magnetic configurations without requiring sustained power. We integrate this architecture into a compact pinch-valve to robustly control pneumatic and liquid media. This state-encoded magnetic control enables logic-embedded fluidic networks, including decoders, hierarchical distribution modules, and a nonvolatile six-port routing array. These systems provide address-based routing and programmable compositional control, offering features like individual port isolation that are impossible with standard mechanically coupled rotary valves. By embedding functionality in persistent magnetic states rather than continuous power or static plumbing, this work establishes a scalable foundation for digital fluidics and autonomous laboratory platforms.

Figures (6)

• Figure 1: Switchable ElectroPermanent Magnet (S-EPM) architecture and polarity switching mechanism. (A) S-EPM assembly components. (B) Labelled magnetic poles of the Switchable Electrostatic Permanent Magnet (S-EPM) in both switched states.
• Figure 2: Design and operating principle of the S-EPM valve. (A) Photograph of the assembled valve, showing the silicone tubing, 3D-printed housing, central S-EPM actuator, and sixteen permanent magnets arranged in four vertically aligned arrays (four magnets per group). (B) Magnetic flux distribution under opposite magnetization states of the S-EPM, illustrating polarity switching within the assembly. (C) Downward actuation state. (i) Photograph of the valve with the lower tube compressed (closed) and the upper tube open. (ii) Schematic of the magnetic configuration with a magnified view of the lower tube deformation, highlighting compression-induced occlusion. (iii) Corresponding excitation pulse (pulse polarity = $-1$) and clockwise magnetization of the Alnico core. (D) Upward actuation state. (i) Photograph of the complementary configuration with the upper tube closed and the lower tube open. (ii) Schematic of the alternate magnetic configuration with a magnified view of the uncompressed lower tube. (iii) Corresponding excitation pulse (pulse polarity = $+1$) and counterclockwise magnetization of the Alnico core.
• Figure 3: Pressure blocking characterization of the S-EPM valve. (A) Photograph of the S-EPM valve integrated with compressible tubing. (B) Experimental setup for pressure-blocking measurements, including regulated air supply, flow meter, upstream ($P_{in}$) and downstream ($P_{out}$) pressure sensors, and venting resistor. (C) Dynamic blocking performance: (i) pressure–time traces at $P_{in}\approx310, 315,$ and $320$ kPa; (ii) cyclic switching at $P_{in}\approx50$ kPa. (D) Transient switching dynamics at $P_{in}\approx100$ kPa: (i) time-resolved single-channel switching transient; (ii) dual-outlet alternating operation showing complementary pressurization profiles. (E) Static sealing tests (Note: Double Y-Axis shows detailed results for $P_{out}$, noise due to analog-to-digital conversion) (i) long-duration blocking at $P_{in}\approx300$ kPa for 20 min with stable upstream pressure and ambient outlet levels; (ii) stepwise upstream pressure ramp from 300 to 500 kPa with corresponding $P_{in}$ and $P_{out}$ traces.
• Figure 4: Architectural configurations of S-EPM-based fluidic routing. (A) Binary routing unit. A single S-EPM valve encodes two bistable magnetic states corresponding to flow (1) or no flow (0). (B) Hierarchical tree-like routing module. A single input ($I_0$) is distributed to four outputs ($Y_0$--$Y_3$) through three cascaded valves. The associated truth table defines the deterministic mapping between valve states and the activated output port, where 0 and 1 denote the two stable logical states of an S-EPM valve (no flow and flow, respectively), and N/A indicates a state irrelevant to the selected routing outcome. (C) Six-port configuration arranged in an alternating input-output sequence around a circular topology. State-encoded control enables routing between adjacent ports and supports independently programmable modes including "All channels closed," "Single-channel isolation," and "Dual-channel isolation." For comparison, a conventional mechanically actuated six-port rotary valve is shown, illustrating its fixed routing pathways and limited reconfigurability. (D) Decoder-like routing configuration in which collective valve states encode a binary address to select a specific output channel from a single input.
• Figure 5: Nonvolatile dual-tree distribution and mixing via cooperative S-EPM valve modules. (A) Layered architecture of the FDM-fabricated mixing module, comprising input, distribution, mixing, transfer, and collection layers for vertically integrated flow management, with outputs directed into a six-well plate. (B) Physical implementation of the dual-tree mixer, featuring two symmetric three-valve S-EPM modules coupled to a central mixing unit with a shared downstream output. (C) Reconfigurable mixing behavior in the dual-tree architecture demonstrated using red and blue dyes as representative inputs. Upon interaction, the two streams produce a purple output, enabling direct visualization of mixing. By switching the valve states, the system transitions between two configurations, resulting in a shift of the mixing region across the six-well plate. The labeled nodes (A1–C2) correspond directly to individual wells, highlighting programmable control over both routing and the spatial location of mixing, with excess flow directed through defined recycle paths. (D) Representative valve state sequence governing dual-tree operation. Values +1 and $-1$ denote the two stable states of each S-EPM valve. Each column corresponds to a distinct system configuration, with the well-plate schematics indicating the resulting distribution pattern. The grey panels in (D) correspond to the grey-highlighted distribution states shown in (C).