Explosion on chip sets liquid in motion

Oct 30, 2008
Simplified version of the micro-bubble actuator developed by Van den Broek. The right illustration shows that the membrane is deflected by the bubble formed near the heater.

(PhysOrg.com) -- PhD student, Dennis van den Broek, of the University of Twente, Netherlands, has developed a new type of miniature motor, the micro-bubble actuator. This ‘motor’, which can be used in laboratories the size of a chip, for instance, converts the energy released during explosive evaporation into motion. Van den Broek will be defending his PhD on 31 October at the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS).

A (micro-)actuator is a device that converts energy, such as magnetic or heat energy into motion. There are many different types of micro-actuators, each with its own advantages and disadvantages. Often actuators are fast or powerful, but not both. However, Van den Broek has designed a micro-actuator that is fast and powerful at the same time. To this end he used heat. This heat is converted into motion by the micro-actuator.

The micro-actuator developed by Van den Broek consists of a cavity filled with a liquid (for instance, ethanol), with a heater at the bottom. The cavity is closed off by a membrane or thin skin that closes the system. Actuators can be found in various places, including in the ‘lab-on-a-chip’, a tiny chemical laboratory the size of a chip. In order to pump liquids through the tiny canals, pumps and valves of the same size are required. The micro-actuator developed by Van den Broek may fulfil a key role in this.

The micro-bubble actuator

In order to make the new actuator powerful and fast, Van den Broek used a promising technology based on explosive evaporation. Explosive evaporation takes place when a liquid is exposed to a high temperature. In a few microseconds the liquid reaches a temperature close to the critical point, far above the boiling point of the liquid in question under normal conditions. At this temperature the liquid evaporates. This is characterized by the formation of a large number of bubbles in the liquid, similar to when water boils. The bubbles formed merge almost immediately to form a layer of vapour. The resulting pressure that builds up is used to deflect a membrane. The 'bulging' of the membrane sets the liquid above it in motion.

Because the bubbles arise in a small volume, the actuator is fast. Van den Broek sent a heat impulse through the heater at least every 0.1 millisecond. This means that a bubble is formed 10,000 times a second and the membrane is deflected. Combined with the high pressure that can be generated by the heat, the actuator is also powerful.

Micro-pumps

The new actuator can be used as a tiny pump in a micro-fluidic system, an example of which is the ‘lab-on-a-chip’. The tiny channels through which the liquid must flow are squeezed together by the bulging, so that the liquid acquires speed. If enough of these micro-actuators are placed one after the other and activated in the right order, the liquid will continue to flow.

Source: University of Twente

Explore further: Researchers bring clean energy a step closer

add to favorites email to friend print save as pdf

Related Stories

Researchers bring clean energy a step closer

2 hours ago

For nearly half a century, scientists have been trying to replace precious metal catalysts in fuel cells. Now, for the first time, researchers at Case Western Reserve University have shown that an inexpensive metal-free catalyst ...

Barclays to allow payments by using Twitter handles

3 hours ago

The next chapter in banks moving into the digital age is a stretch beyond reminding customers over phone lines that they can also bank online. Barclays has launched Twitter payments through Pingit.

Predicting human crowds with statistical physics

3 hours ago

For the first time researchers have directly measured a general law of how pedestrians interact in a crowd. This law can be used to create realistic crowds in virtual reality games and to make public spaces safer.

Recommended for you

Researchers bring clean energy a step closer

Feb 27, 2015

For nearly half a century, scientists have been trying to replace precious metal catalysts in fuel cells. Now, for the first time, researchers at Case Western Reserve University have shown that an inexpensive metal-free catalyst ...

The construction of ordered nanostructures from benzene

Feb 27, 2015

A way to link benzene rings together in a highly ordered three-dimensional helical structure using a straightforward polymerization procedure has been discovered by researchers from RIKEN Center for Sustainable ...

Superatomic nickel core and unusual molecular reactivity

Feb 27, 2015

A superatom is a combination of two or more atoms that form a stable structural fragment and possess unique physical and chemical properties. Systems, that contain superatoms, open a number of amazing possibilities ...

Oat breakfast cereals may contain a common mold-related toxin

Feb 25, 2015

Oats are often touted for boosting heart health, but scientists warn that the grain and its products might need closer monitoring for potential mold contamination. They report in ACS' Journal of Agricultural and Food Chemistry that s ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

crisw
not rated yet Oct 31, 2008
A method very close to this was described in IEE Electronics Letters, ca. 1967, as an interface between electrical and fluidic systems.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.