Machines made of soft materials bridge life sciences and engineering1. Advances in soft materials have led to skin-like sensors and muscle-like actuators for soft robots and wearable devices1-3. Flexible or stretchable counterparts of most key mechatronic components have been developed4,5, principally using fluidically driven systems6-8; other reported mechanisms include electrostatic9-12, stimuli-responsive gels13,14 and thermally responsive materials such as liquid metals15-17 and shape-memory polymers18. Despite the widespread use of fluidic actuation, there have been few soft counterparts of pumps or compressors, limiting the portability and autonomy of soft machines4,8. Here we describe a class of soft-matter bidirectional pumps based on charge-injection electrohydrodynamics19. These solid-state pumps are flexible, stretchable, modular, scalable, quiet and rapid. By integrating the pump into a glove, we demonstrate wearable active thermal management. Embedding the pump in an inflatable structure produces a self-contained fluidic 'muscle'. The stretchable pumps have potential uses in wearable laboratory-on-a-chip and microfluidic sensors, thermally active clothing and autonomous soft robots.

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Stretchable pumps for soft machines

Micropumps and biomedical applications – A review

Recent trends in mechanical micropumps and their applications: A review

During recent years the universal interest in trace elements has simulated a number of studies of their concentration and distribution in the human cancer cells, with the purpose of establishing the normal values and also to detect cancer, occupational cancer and toxic effects. Nanoparticles exist in the environment and in a variety of compounds with different properties

A Comparative Study on Simultaneous Determination and Separation of Adsorbed Cadmium Oxide (CdO) Nanoparticles on DNA/RNA of Human Cancer Cells Using Biospectroscopic Techniques and Dielectrophoresis (DEP) Method

We studied whether several agents, approved or undergoing trials in human glaucoma, were effective in preventing ganglion cell loss in the DBA/2J mouse. Adult DBA/2J mice were treated with timolol, pilocarpine, brimonidine, dorzolamide, or NMDA-receptor antagonist memantine. Surviving retinal ganglion cells of treated and control mice were retrogradely labeled with fluorogold and counted after whole mount preparation. In treated mice, only memantine and timolol had significant effects on retinal ganglion cell survival (P<0.0001, analysis of variance). Brimonidine was lethal to these mice, and these retinae were not analyzed further. The DBA/2J mouse represents a promising candidate for further experimentation in ocular hypertension.

Effects of Anti-glaucoma Medications on Gangion Cell Survival: The DBA/2J Mouse Model

Micropumps are finding more applications in biomedical fields. One application that holds great potential for micropumps is the treatment of glaucoma. Shunts are currently used in the treatment glaucoma. They lower intraocular pressure by passively increasing the outflow of aqueous humour from the anterior chamber in the eye. Nozzle/diffuser micropumps are an attractive alternative to shunts. They would provide both passive outflow and variable active outflow of aqueous humour as necessary. They would be able to overcome increases in flow resistance caused by biofouling and scar tissue growth. This study presents a proof of concept of a 1-mm-thick electromagnetic PDMS nozzle/diffuser micropump for biomedical applications. The pump is composed of a cast PDMS body, a spin coated PDMS membrane, and commercial silicone tubing, all bonded together with PDMS. Micromachining a pump cast enables multiple pumps to be produced quickly and reliably. An in-plane design is used to attach the inlet and outlet tubes. The pump produces a peak flow rate of 135 μL/min and a maximum backpressure of 25 mmH2O at an actuation frequency of 12 Hz and a duty cycle of 25%. The membrane thickness, actuator type, and duty cycle were shown to have a significant impact on the performance of the pump.

A thin PDMS nozzle/diffuser micropump for biomedical applications

Background Glaucoma is the second leading cause of blindness in the world and the first leading cause of irreversible vision loss. Currently, the primary methodology of testing for the intraocular pressure (IOP) is during clinical office hours, which only provide a limited amount of information on the trends and fluctuations of the IOP. Therefore, a continuous monitoring system is required to properly determine the peaks of pressure and to negate any false results obtained by sparse, clinic hour testing. The objective of this study is to determine the ability of a newly designed contact lens with an embedded microchannel, to accurately measure the fluctuations in the IOP. Methods Experimentation was completed on fresh enucleated porcine eyes. The contact lens was placed on the porcine eye and utilising a camera the fluid movement, within the microchannel in the contact lens, was recorded. A micro-pressure catheter, threaded into the centre of the vitreous chamber, recorded the true IOP and was compared with the displacement of the indicator fluid within the microchannel. Results The contact lenses showed a consistent linear responsiveness to changes in IOP and robust to the effects of anatomical differences among eyes. The indicator fluid had an average fluid movement of 28 um/mm Hg between all the trials. Additionally, the devices showed the ability to measure both increases and decreases in IOP during cyclical fluctuations. Conclusion The described inexpensive and non-invasive sensor is able to reliably monitor the IOP changes based on porcine eye model.

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Non-invasive Intraocular pressure monitoring with contact lens

A cantilever biosensor with integrated electrodes for piezoelectric actuation and electrokinetic capture is used to detect cells in real time. The sandwich electrodes used for electrokinetic capture present advantages over side-by-side electrodes in terms of reducing the gap size between electrodes and the structural mass added to the cantilever. The 5th resonant mode (≈617 kHz) of the biosensor provided a signal-to-noise ratio of 82 within 10 min when E. coli was measured from a stagnant sample with a concentration of 107 cells/ml. The 7th resonant mode (≈1160 kHz) provided a signal-to-noise ratio of 26 within 10 min when E. coli was measured from a flowing sample (400 μl/min) with a concentration of 105 cells/ml. The estimated sensitivity of the 7th resonant mode is 326 fg/Hz based on images of captured cells.

A cantilever biosensor exploiting electrokinetic capture to detect Escherichia coli in real time

Dynamic-mode cantilever biosensors are an attractive technology for measuring the presence or concentration of biological particles in a sample, but their performance is severely reduced in liquid due to damping. A few techniques have emerged to overcome damping, including the use of millimeter-sized cantilevers and suspended microchannel resonators. Here we present a newly discovered technique to overcome damping and obtain strong responses in liquid. E. coli cells are collected in a micron-sized gap at the free end of a cantilever using electrokinetic effects and they are measured in real time using the frequency shift of the fundamental resonant frequency of the cantilever. The effect of gap size, cantilever usage, and electrokinetic voltage are analyzed. Measurements are performed without surface functionalization, flow, or a frequency tracking circuit using samples with concentrations as low as 100 cells/ml.

A cantilever biosensor based on a gap method for detecting Escherichia coli in real time

An hourglass design that enables electrokinetic sampling and electrothermal actuation for detecting waterborne pathogens with micro biosensors is presented The hourglass component creates a large potential drop suitable for dielectrophoresis and serves as a V-shaped microelectrothermal actuator for structural measurements Escherichia coli bacteria from a stagnant 5 μl sample were collected within 15 min with a signal of 5 V peak-to-peak (Vpp) at 1 kHz The bacteria were detected by measuring resonant frequency shifts of the first eight modes of the microstructure, and a maximum sensitivity of 204 ± 53 fg/Hz was achieved with the seventh mode The hourglass component is a unique design solution that combines structural excitation and electrokinetic sampling for micro biosensors

Stephane Leahy

Papers

A thin PDMS nozzle/diffuser micropump for biomedical applications

Non-invasive Intraocular pressure monitoring with contact lens

A cantilever biosensor exploiting electrokinetic capture to detect Escherichia coli in real time

A cantilever biosensor based on a gap method for detecting Escherichia coli in real time

An hourglass design with electrokinetic sampling and electrothermal actuation for micro biosensors