Metachronal μ-Cilia for On-Chip Integrated Pumps and Climbing Robots

Abstract

Biological cilia often perform metachronal motion, that is, neighboring cilia move out of phase creating a travelling wave, which enables highly efficient fluid pumping and body locomotion. Current methods for creating metachronal artificial cilia suffer from the complex design and sophisticated actuation schemes. This paper demonstrates a simple method to realize metachronal microscopic magnetic artificial cilia (μMAC) through control over the paramagnetic particle distribution within the μMAC based on their tendency to align with an applied magnetic field. Actuated by a 2D rotating uniform magnetic field, the metachronal μMAC enable strong microfluidic pumping and soft robot locomotion. The metachronal μMAC induce twice the pumping efficiency and 3 times the locomotion speed of synchronously moving μMAC. The ciliated soft robots show an unprecedented slope climbing ability (0 to 180°), and they display strong cargo-carrying capacity (>10 times their own weight) in both dry and wet conditions. These findings advance the design of on-chip integrated pumps and versatile soft robots, among others.

Amphibious Transport of Fluids and Solids by Soft Magnetic Carpets

“…The flow speed increased with increasing angular frequency, but appeared to plateau for our highest frequencies, this is reminiscent of some of the observations found in refs. [ 31 , 35 ]. We also considered the flow efficacy.…”

“…We observed a flow reversal by switching from water to glycerol (see Figure 5d – f ), analogous to the one reported in ref. [ 35 ]. We will explore this phenomenon next.…”

“…[ 46 , 47 , 48 ] Here, we go beyond the results of ref. [ 35 ] by examining a range of viscosities, we do so by preparing a series of aqueous polyvinylpyrrolidone (PVP, 360k) solutions up to 20% of PVP by weight (corresponding viscosities in Table S2 , Supporting Information). For an SMC with a pillar aspect ratio of 3.1, the liquid flow in deionized (DI) water (0% PVP) was comoving (see Figure 5d and Movie S10 , Supporting Information).…”

“…The efficiency of the ciliated fluid transport has motivated scientists to mimic this strategy, primarily to replicate the biological functionality. [ 30 , 31 , 32 , 33 , 34 , 35 ] Additionally, biomimetic cilia can be driven by external fields with relative ease. [ 30 , 31 , 32 , 36 , 37 ] A recent demonstration thereof includes solid cargo transport employing electric fields in a liquid environment (silicone oil).…”

Fluid Flow Induced Deformation of a Boundary Hair

“…With the improvement of existing manufacturing techniques and the creation of new protocols [23][24][25][26][27][28], studies have investigated increasing small, high aspect-ratio systems of artificial hairs. For example, recent studies have investigated the design potential of hair beds: Hairs placed in a microfluidic channel have been shown to function as pumps [27,29,30], rectifiers [31,32], and micro-mixers [33][34][35] making them a design consideration in lab-on-chip devices.…”