Abstract
A mechanical flip-flop actuator has been developed that allows for the facile re-routing and distribution of liquid marbles (LMs) in digital microfluidic devices. Shaped loosely like a triangle, the actuating switch pivots from one bistable position to another, being actuated by the very low mass and momentum of a LM rolling under gravity (~4 × 10−6 kg ms−1). The actuator was laser-cut from cast acrylic, held on a PTFE coated pivot, and used a PTFE washer. Due to the rocking motion of the switch, sequential LMs are distributed along different channels, allowing for sequential LMs to traverse parallel paths. This distributing effect can be easily cascaded, for example to evenly divide sequential LMs down four different paths. This lightweight, cheap and versatile actuator has been demonstrated in the design and construction of a LM-operated mechanical multiplication device — establishing its effectiveness. The actuator can be operated solely by gravity, giving it potential use in point-of-care devices in low resource areas.
Highlights
Liquid Marbles (LMs) are small droplets of liquid that have been coated in a nano- or micro-powder[1]
In our design the data signals are represented by liquid marbles (LMs), and the result of the computation is displayed in the positioning of the bi-stable flip-flop actuators
The flip-flop actuators, visible in Fig. 1, are small and lightweight switches that can be reliably actuated by the low mass of a LM — approximately 18 mg in this case
Summary
Liquid Marbles (LMs) are small droplets of liquid that have been coated in a nano- or micro-powder[1]. Whilst an aqueous droplet with a hydrophobic particle coating is by far the most common form of a LM, there are examples using an organic liquid core and oleophobic coating[2] This phenomenon results in the ability to transport microlitre quantities of liquid around, with zero loss due to surface adhering/wetting. This, combined with the ease of tuning a LM’s core and coating, allows for an elegant system This collision-based system, requires the precise synchronisation of the data signals (i.e. the LMs). Whilst this has been achieved with the use of magnetic LMs and synchronised electromagnets, it places an additional burden on the experimental computational setup. In our design the data signals are represented by LMs, and the result of the computation is displayed in the positioning of the bi-stable flip-flop actuators
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