A single four-digit, seven-segment display would typically require 29 solenoid valves to control directly, but millifluidic logic reduces that hardware footprint to just 11 valves.
Replacing MOSFETs with Vacuum-Powered Transistors
Fluidic circuits operate on the pressure difference between atmospheric pressure (logical 0) and a near-vacuum of approximately -60 kilopascals (logical 1). In this architecture, a flexible membrane is sandwiched between rigid layers containing networks of air channels. To mimic a metal-oxide-semiconductor field-effect transistor (MOSFET), a vacuum "transistor" uses a flow layer with source and drain chambers divided by a central valve seat, and a control layer containing a gate cavity.
Applying a vacuum to the gate chamber pulls the membrane into the cavity, lifting it off the seat and allowing airflow between the source and drain. This mechanism, combined with fluidic resistors and check valves that act as diodes, allows for the construction of a full suite of logic gates. Unlike traditional microfluidics fabricated from etched glass, these millifluidic devices can be produced using 3D printing and silicone casting, provided that printing parameters like elevated temperatures and slight overextrusion are used to eliminate porosity.
Using Capacitance-Like Memory for Soft Displays
Standard electronic LED displays use high-speed strobing to create the illusion of simultaneous illumination, a feat impossible with pressurized air. Instead, this soft clock treats each segment like a capacitor. By evacuating a segment's underlying cavity, the system "charges" it (logic 1); restoring atmospheric pressure "discharges" it (logic 0).
Each digit effectively acts as an independent 7-bit memory. The system utilizes a seven-line data bus where each line connects to a solenoid valve providing either vacuum or atmospheric pressure. To selectively address digits, fluidic transistors are placed between each segment and its data line. A "write enable" line, controlled by its own solenoid valve, combines the transistor control inputs for a specific digit. This allows the clock to update one digit per second, with a full cycle across the face taking 4 seconds.
This integration of computation and actuation moves us closer to a class of machines that are lighter and more integrated, where the same medium used for movement also handles the logic. The next step in this evolution involves scaling these vacuum-powered logic systems into more complex, autonomous soft robotic platforms.
Source: Make a Soft Digital Clock Tick With Millifluidics
Domain: spectrum.ieee.org
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