The principles of cascading power limits in small, fast biological and engineered systems
Mark Ilton, M. Saad Bhamla, Xiaotian Ma, Suzanne M. Cox, Leah L. Fitchett, Yongjin Kim, Je-sung Koh, Deepak Krishnamurthy, Chi-Yun Kuo, Fatma Zeynep Temel, Alfred J. Crosby, Manu Prakash, Gregory P. Sutton, Robert J. Wood, Emanuel Azizi, Sarah Bergbreiter, S. N. Patek
Science, Vol 360, No. 6387, 27 Apr 2018
Rapid behavioral transitions produce chaotic mixing by a planktonic microswimmer
William Gilpin, Vivek N. Prakash, Manu Prakash
ArXiv doi: ArXiv:1804.08773 Apr 2018
Ultra-fast cellular contractions in the epithelium of T. adhaerens and the “active cohesion” hypothesis
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Two-component Marangoni-contracted droplets: friction and shape
Adrien Benusiglio, Nate Cira, and Manu Prakash
Accepted in Soft-matter, arXiv:1712.00153, Nov 2017
Two-component self-contracted droplets: long-range attraction and confinement effects
Adrien Benusiglio, Nate Cira, Anna Wei Lai and Manu Prakash
submitted to PNAS, arXiv:1711.06404, Nov 2017
Synchronous magnetic control of water droplets in bulk ferrofluid
Georgios Katsikis, Alexandre Bréant, Anatoly Rinberg, Manu Prakash
Soft Matter 2018, 14, 681-692 doi: 10.1039/c7sm01973d, Nov. 2017
Using mobile phones as acoustic sensors for high-throughput mosquito surveillance
Haripriya Mukundarajan, Felix Hol, Erica A Castillo, Cooper Newby, Manu Prakash
eLife 2017;6:e27854 DOI: 10.7554/eLife.27854
Mapping load-bearing in the mammalian spindle reveals local kinetochore-fiber anchorage that provides mechanical isolation and redundancy
Current Biology Volume 27, Issue 14, 24 July 2017, Pages 2112-2122.e5
Generation of droplet arrays with rational number spacing patterns driven by a periodic energy landscape
Anatoly Rinberg, Georgios Katsikis, Manu Prakash
Physical Review E Volume 96, September 15, 2017, Pages 033108.
Reply to Boundary effects on currents around ciliated larvae
William Gilpin, Vivek Prakash, Manu Prakash
Nature Physics, Volume 13, No. 6, Pages 521–522, 2017.
Paperfuge: An ultra-low cost, hand-powered centrifuge inspired by the mechanics of a whirligig toy
M. Saad Bhamla, Brandon Benson*, Chew Chai*, Georgios Katsikis, Aanchal Johri, Manu Prakash
* equal contribution
Nature Biomedical Engineering Vol. 1, No. 1, pp. 1-7, 2017.
Schistosoma mansoni cercariae exploit an elastohydrodynamic coupling to swim efficiently
Deepak Krishnamurthy, Georgios Katsikis, Arjun Bhargava, Manu Prakash
Nature Physics Vol. 13, No. 3, pp. 266-271, 2017.
Surface tension dominates insect flight on fluid interfaces
Haripriya Mukundarjan, Thibaut Bardon, Dong Hyun Kim and Manu Prakash
Journal of Experimental Biology, Vol. 219, No. 5, pp. 752-766, 2015.
Diagnosis of Schistosoma haematobium Infection with a Mobile Phone-Mounted Foldscope and a Reversed-Lens CellScope in Ghana
Richard K. D. Ephraim, Evans Duah, James S. Cybulski, Manu Prakash, Michael V. D’Ambrosio, Daniel A. Fletcher, Jennifer Keiser, Jason R. Andrews and Isaac I. Bogoch
American Journal of Tropical Medicine and Hygiene, Vol. 14-0741, 2015
Foldscope: Origami based paper microscope
James S. Cybulski, James Clements and Manu Prakash
PLoS ONE, Vol. 9, No. 6, pp. 1-11, 2014.
Another poem was pointed out to me, by an annonymous user of Foldscope. Soon we are shipping 50,000 microscopes to people in 130 countries in the world. That is a lot of work; but the joy is tremendous.
Dr. Henry Power’s poem on the Microscope
Microscopicall observations (1661)
In Comendation of ye Microscope.
Of all th’ Inuentions none there is Surpasses
the Noble Florntine’s Dioptrick=glasses.
For what a better, fitter, guift Could bee
in this world’s Aged Luciosity.
To Helpe our Blindnesse so as to deuize
a paire of new and Artificiall eyes.
By whose augmenting power wee now see more
then all the world Has euer donn Before.
Thy Atomes (Brause Democritus) are now
made to appeasre in bulk and figure too.
when Archimide by his Arithmatick,
The full poem is online.
The hungry fly: Hydrodynamics of feeding in the common house fly
M. Prakash and M. Steele *
Physics of Fluids, Vol. 23, No. 2011
The poem by William Oldys perfectly sums up this work which started as a curious inquiry into the nature of pumps in insects. Entomologists have long described the physical layout of mechnical machines we call insects, but the dynamics of how these machines work has never been seen before. Miles and I rigged up Xray microscopy setups to image insects in all the glory (in-vivo). From what we can tell, these are some really efficient pumps.
On a Fly Drinking Out of His Cup
Busy, curious, thirsty fly!
Drink with me and drink as I:
Freely welcome to my cup,
Couldst thou sip and sip it up:
Make the most of life you may,
Life is short and wears away…
By William Oldys (1696-1761)
Face-selective electrostatic control of nanowire synthesis
J. Joo, B. Chow, M. Prakash, E. Boyden, J. Jacobson
Nature Materials Vol. 10, 596-601 (2011)
Interfacial propulsion by directional adhesion
M. Prakash and J. Bush
Int. J. of Nonlinear Mechanics, Vol. 46, 607-615 (2011)
So you are sitting on a pond, watching tiny rain drops hit the surface and ripple along. It’s all peace and quiet on the surface of a pond. But suddenly comes a “water strider” a cheetah of the surface tension world zipping along the water like nobody’s business (~0.5 m/sec). But wait, didn’t all the scanning electron microscopy images show that the legs of a water strider (and almost all the 1800 other species) are superhydrophobic. So if you don’t touch the fluid interface, how do you generate such high traction forces. I built a fluid-interface force spectroscopy setup to measure direct propulsion forces generated by individual superhydrophobic surface – and “aha” to our surprise, water strider legs exhibit unidirectional anisotropy. What that means is the surface has a preferential direction in which a fluid contact line would happily move along one direction on a surface but have a high resistance when moving along another. This work has now inspired a large number of “unidirectional superhydrophobic surfaces” with commercial applications. But wait, water striders thought of this idea millions of years ago.
On a tweezer for droplets
J. Bush, F. Peaudecerf, M. Prakash, D. Quere
Advances in Colloid and Interface Science, Vol. 161, 10-14 (2010)
In physics, ratchets are mechanisms that generate symmetry breaking (due to physical principles) from periodic energy landscape (or motion). A lot of them have been discovered, from a brownian ratchet to an optical ratchet. Here we describe a “capillary ratchet” generated by an asymmetry in contact-angle hysteresis leading to unidirectional droplet propulsion. Sometimes asymmetries can be so mind-bending.
Drop propulsion in tapered tubes
P. Renvoise, J. Bush, M. Prakash and D. Quere
Euro Physics Letters, Vol. 86, 1-5 (2009)
Take a small pool of water and dip a fine glass capillary. Voila! the water rises up almost as if something is pulling it up (and something is pulling it up). This experiment was done and basically understood in the 1600’s. But now take a conical capillary. Put a drop of water and watch what happens. The drop will spontaneously move towards the narrow end due to the LaPlace pressure gradient generated due to the taper. Though this is such a simple geometrical configuration, fluid flow in a tapered tube is non-trivial. Here we derive a stability criteria for tapered tubes of all shapes and form.
Surface tension transport of prey by feeding shorebirds: The capillary ratchet
M. Prakash, D. Quere and J. Bush
Science, Vol. 320 (5878), 931-934 (2008)
Darwin was fascinated with bird beaks (amongst other things Darwin was fascinated with). Shape and form in biology (from the perfect beak of a bird to swimming paddle of a blue whale) evolve to optimize for function. But as with everything else in biology, it’s often hard to tell how optimal is something (mathematically speaking). From an observation I made on a lake of a shore bird so fascinating (it catches your attention right away when you see it spinning in circles, all the time), I stumbled on an unusual strategy they use to transport fluids through the beak utilizing contact angle hysteresis. Usually contact angle hysteresis impedes motion, the reason why a drop of water sticks to window glass on a rainy day. Here was a case when this is the only reason the droplets are transported. We ended up calling this mode of transport a “capillary ratchet.” The bird beak geometry is optimized in several species to take advantage of this physical principle. What else could have Darwin asked for – maybe a mathematical equation for his “finch” beaks.
The integument of water-walking arthropods: Form and function
J. Bush, D. Hu, M. Prakash
Advances in Insect Physiology, Vol. 34 117-192 (2007)
Here we review the fascinating diversity of insect cuticle found in water-walking arthropods, from spiders to beetles and everything in the middle. A fluid interface acts as an ecological niche so wonderful, with fascinating adaptations from locomotion to breathing underwater. Yes breathing underwater – by diving down with tiny little surface bubbles. That’s equivalent of a physical lung made out of a bubble.
Water walking devices
D. Hu, M. Prakash, B. Chan, J. Bush
Experiments in Fluids, Vol. 43, 769-778 (2007)
So if insects can walk on water, why should we stand back. Here we attempt to make machines capable of walking on water (and succeed). Not an easy challenge considering surface tension supports very little weight. Though if you were to wear a shoe several kilometer in size, you might be able to stand on water. That is a start.
Microfludic Bubble Logic
M. Prakash, N. Gershenfeld
Science Vol. 315, 832-835 (2007)
For the last 100 years, computation has been used as a mechanism for information processing. Even though physical laws directly enforce a necessary association of bits of information with physical entities (e.g. electrons in a microprocessor or pieces of chalk on a board), computation has not been developed as a paradigm for algorithmic assembly of physical materials. To make computation explicitly physical (literally), We invented a new logic family purely implemented in multi-phase Newtonian fluids that merge chemistry and computation, opening doors for algorithmic manipulation of entities at a mesoscale (1-100 microns). Welcome to the world of tiny little bubbles zipping in fluidic networks talking to each other (hydrodynamically speaking) implementing functions you desire.
N. Gershenfeld, M. Prakash
Telektronikk Vol. 3, 22-26 (2004)
Inspired by the open wireless revolution, we developed a process where anybody could “print” high gain antennas for wireless devices and paste it on the window glass pane. DIY high-gain antennae that costs a couple cents. That’s got to be good for something.