Force Pattern Characterization of C. elegans in Motion

 

BNN Members involved:

Shazlina Johari
Volker Nock
Maan Alkaisi

Description

C. elegans is a multicellular eukaryotic nematode living in temperate soil environments. Due to its relative simplicity in anatomy, C. elegans has been used extensively as a model organism for studies on cellular differentiation, neural networking and genetic modification in eukaryotes. It was the first multicellular organism to have its genome completely sequenced. Commonly in biological study, the worm C. elegans can be genetically modified to obtain mutants with different number of muscle arms, which in turn affect the motion patterns of the nematode. It is of biologists’ particular interest to study the correlation between muscle arms and motion patterns, e.g., if there is a positive relationship such that the mutant with more muscle arms generates greater motion forces.

As the worm is tiny (~1mm in length and < 100μm in width, invisible to naked eyes) and dynamic, traditional sensors in macroworld cannot be used to measure the force. This project uses a silicon-based organic elastomer polydimethylsiloxane (PDMS) device and computer vision based method, which are capable of characterizing the force patterns of the worm in motion. To measure the force, the worm is put inside the open channel formed by the two parallel arrays of pillars of the PDMS device. When crawling in a sinusoidal manner, the worm bends the pillars, whose deflection can be sensed by a camera. By the established force-deflection model of the pillars, the force of C. elegans in motion can be resolved from the deflection obtained via image processing.

Using a compilation of three clips, the video below introduces a microdevice capable of constantly measuring the force of nematodes in motion. The system consists of a micropillar-based device made of flexible polydimethylsiloxane (PDMS) and a vision-based algorithm for resolving force from the deflection of the cantilever-like pillars.

Clip 1 shows a dual row pillar array for the measurement of nematode sinusoidal movement. Pillar deflections are small in this layout and ongoing work is aimed at allowing one to better match worm size to array spacing by including a nematode sorter.

Clip 2 shows nematode movement through a quadruple pillar array. The custom software algorithm tracks and detects nematode-pillar contact in real-time. The results can also be used as feedback for an automated microscope stage.

Clip 3 shows an example application of the software for calibrated force measurement. The direction and length of the blue arrows are equivalent to the direction and magnitude of the force applied by the nematode to the respective pillar. The microdevice, combined with sub-pixel resolution for visually tracking the deflection, and the experimental technique form a powerful integrated system for measuring dynamic forces of moving nematodes.

Video

Relevant Publications:

AuthorsTitleJournalVolumePagesYearLink
S. Johari, V. Nock, M.M. Alkaisi and W. WangOn-chip analysis of C. elegans muscular forces and locomotion patterns in microstructured environmentsLab on a Chip13 (9)1699–17072013paper
A. Ghanbari, V. Nock, S. Johari, R. J. Blaikie, X-Q. Chen and W. WangMicropillar-based on-chip system for continuous force measurement of C. elegansJournal of Micromechanics and Microengineering22 (9)0950092012paper
S. Johari, V. Nock, M. M. Alkaisi and W. WangHigh-Throughput Microfluidic Sorting of C. elegans for Automated Force Pattern MeasurementMaterials Science Forum700182-1872011paper
A. Ghanbari, V. Nock, W. H. Wang, R. J. Blaikie, J. G. Chase, X. Q. Chen and C. E. HannForce pattern characterization of C. elegans in motionInternational Journal of Computer Applications in Technology39 (1-3)137-1442010paper