Manu Prakash : Research : Bubble Logic

Nonlinear bubble interactions by hydro-dynamic force fields are exploited to build universal logic gates operating at low Re number in newtonian fluids.
Microfluidic memory

Bistable one-bit bubble memory for storage of both information and chemicals at the same time.

Bubble circuits

Bubble logic devices can be cascaded to form numerous digital circuit elements like ring oscillators, counters.

Bubble synchronization

Non-linear fluidic ladder networks are used to synchronize two streams of bubbles, thus correcting any timing error.

Bubble modulator

Bubbles can be generated on demand to encode information in a train of bubbles. 

We have invented a new logic family which implements universal Boolean logic, bistability and numerous other traits associated with a scalable logic family using immiscible fluids in microfluidic geometries. A bubble in a channel represents a bit. But unlike electronics, a bit of information can also carry a chemical payload, allowing us to manipulate materials and information at the same time. This paradigm ties together chemistry and computation.

We describe various AND/OR/NOT gates exhibiting amplification, toggle flip-flop exhibiting bistable one-bit memory, counters, cascaded circuits like ring oscillator, bubble synchronizer and so on. The logic family can be used to control segmented flow reactors (droplet reactors) in a scalable manner without any external control elements. The platform technology greatly simplifies design of large scale microfluidic "lab on chip" systems with applications in high throughput screening, combinatorics, integrated optofluidics and printing technologies.

[1] Microfluidic Bubble Logic, M. Prakash, N. Gershenfeld, Science, 9 Feb. 2007.
Image Gallery

Fig. Microfluidic ring oscillator with three AND gates and three delay lines in a  ring configuration, depicting cascadability and feedback implemented in bubble logic devices. Image inverted, colorized.
(Image credit : Manu Prakash).

Fig. Passive microfluidic bubble synchronizer depicting error correction/timing restoration in bubble logic. The device is implemented as a non-linear ladder network which synchronizes two stream of bubbles. Bubble travel from left to right (faded to depict time stamp), arriving with a time lag, but leaving simultaneously.
(Image credit : Manu Prakash).

Fig. Micrograph depicting a bubble modulator and toggle flip-flop. The modulator converts an electric pulse (applied to a micro-heater) into a bubble train while the flip-flop stores one-bit of information in a passive bistable memory.
(Image credit : Manu Prakash).

Fig Microfabricated bubble logic chip with PDMS molded microchannels, and platinum bubble modulators integrated into one device. 
(Image credit : Manu Prakash).

Fig. Photograph of a bubble logic chip in operation. A series of bubbles fall out from the outlet (image inverted)
(Image credit : Manu Prakash).

Fig. Universal gate, implementing AND and NOT in the same device. Bubble logic gates conserve the number of bits entering and exiting the device, since bubbles are neither produced nor destroyed in the logic operation.
(Image credit : Manu Prakash)

Fig. Lab setup with a ring oscilllator  on the screen.
(Image credit : Donna Coveney)

Fig. Microfluidic AND/OR logic gate with arrows marking the direction of flow. The device computes A+B and A.B simultaneously.
(Image credit : Manu Prakash)

Fig. Micrograph of a SU8 mold for fabricating cascaded logic gates.
(Image credit : Manu Prakash)

Fig. Stable microfluidic ring oscillator constructed by connecting three AND gates and three delay lines. Colored bubble represents a bubble in the delay line which results in a cascaded switching of gates in the ring structure.
(Image credit : Felice Frenkel, Manu Prakash)

Fig. Microfluidic one bit memory implemented as a  toggle flip-flop. Yellow bubble in the bottom lobe represents a zero. Orange bubble arrives from the left as a toggle signal, switching the state of the device from zero to one.
(Image credit : Manu Prakash)

Fig. Microfluidic bubble synchronizer capable of passively synchronizing two bubble data streams. Bubble flow from right to left, arriving with a time lag but leaving in a synchronized manner.
(Image credit : Manu Prakash)

Fig. Microfluidic electro-bubble modulator used for encoding information in a bubble train.
(Image credit : Manu Prakash)

Fig. Microfluidic bubble ring oscillator in a stable state before initation of oscillations. Small perturbation in the system results in an oscillating system. Image threshold applied.
(Image credit: Manu Prakash)

Fig. MIT logo written using micro-bubbles captured by a soap film of the same shape.
(Image credit : Manu Prakash)

Last Updated : 8 Feb. 2007