Control and manipulation of microfluidic flow via elastic deformations

Abstract

We utilize elastic deformations via mechanical actuation to control and direct fluid flow within a flexible microfluidic device. The device consists of a microchannel with a flexible arch prepared by the buckling of a thin elastic film. The deflection of the arch can be predicted and controlled using the classical theory of Euler buckling. The fluid flow rate is then controlled by coupling the elastic deformation of the arch to the gap within the microchannel, and the results compared well with analytical predictions from a perturbation calculation and numerical simulations. We demonstrate that placement of these flexible valves in series enables directed flow towards regions of externally applied mechanical stress. The simplicity of the experimental approach provides a general design for advanced functionality in portable microfluidics, self-healing devices, and in situ diagnostics.

Universal poroelastic mechanism for hydraulic signals in biomimetic and natural branches

“…This finding confirms and explains the paradox previously hypothesized about the origin of hydraulic pulses induced by bending in plants (23). In an engineering context, it could also be applied to artificial devices like microfluidic pumps or soft robots to rectify pressure and fluid flow under oscillatory motion (32,43). The simple poroelastic model we built shows that the key parameter controlling the amplitude of the pressure response is the elastic bulk modulus of the branch, a mechanical property that mainly depends on the Young's modulus of the branch.…”

“…To this end, we use a biomimetic approach (26)(27)(28)(29) and study the hydraulic response to bending of soft artificial branches that mimic the basic structural and mechanical features of natural stems and branches. While previous theoretical and experimental works have studied the linear behavior of poroelastic beams (30)(31)(32), very few have investigated the large deformation regime of fluid-infiltrated media composed of cellular materials like wood or soft plant tissues (33). In this work, we…”

Passive Control of Viscous Flow via Elastic Snap-Through

“…This arch height was varied within the channel assembly by changing the length of the strip prior to clamping. The difference between the natural length of the strip, L strip , and the horizontal distance between the two clamping points is referred to as the end-shortening ∆L = L strip − L L; for shallow arches ∆L is related to the arch amplitude by w 0 ≈ 2(L ∆L) 1/2 /π (using the Euler-buckling mode w(x) = w 0 1 − cos(2πx/L) /2 [5]). …”

“…For example, the Quake valve [3,4] allows flow in a primary channel to be blocked off by inflating control channels. Channel flexibility has been exploited to control flows by bending the device [5], applying a varying potential difference to create a microfluidic pump [6] or simply by turning mechanical screws to constrict flow [7].…”

Spatially Configuring Wrinkle Pattern and Multiscale Surface Evolution with Structural Confinement

“…[8][9][10][11][12][13] The latter perspective has enabled engineering opportunities with self-adaptive/autonomous structures in low dimensions and has implications in many different contexts such as micro-/ nanofluidics, [14][15][16] flexible electronics, [17,18] adhesion, [19,20] organic solar cells, [21] tunable optics, [22][23][24] wettability, [25][26][27] and promising methods for surface patterning. [1,[28][29][30][31] While our scientific/technical understanding has advanced, there remains much to be explored about the control of instability morphology, and in particular how to configure instabilities, such as wrinkling and creasing, to desired patterns with selective distribution covering the surface and bespoke thresholds for the formation and evolution of instabilities.…”