Osmosis-Based Pressure Generation: Dynamics and Application

Abstract

This paper describes osmotically-driven pressure generation in a membrane-bound compartment while taking into account volume expansion, solute dilution, surface area to volume ratio, membrane hydraulic permeability, and changes in osmotic gradient, bulk modulus, and degree of membrane fouling. The emphasis lies on the dynamics of pressure generation; these dynamics have not previously been described in detail. Experimental results are compared to and supported by numerical simulations, which we make accessible as an open source tool. This approach reveals unintuitive results about the quantitative dependence of the speed of pressure generation on the relevant and interdependent parameters that will be encountered in most osmotically-driven pressure generators. For instance, restricting the volume expansion of a compartment allows it to generate its first 5 kPa of pressure seven times faster than without a restraint. In addition, this dynamics study shows that plants are near-ideal osmotic pressure generators, as they are composed of many small compartments with large surface area to volume ratios and strong cell wall reinforcements. Finally, we demonstrate two applications of an osmosis-based pressure generator: actuation of a soft robot and continuous volume delivery over long periods of time. Both applications do not need an external power source but rather take advantage of the energy released upon watering the pressure generators.

Fast nastic motion of plants and bioinspired structures

“…For example, the leaves of the Mimosa plant, which contract upon certain external stimuli (physical, heat, chemical etc. ), have inspired research in structures that can change on demand between flexible and stiff states through changes in hydraulic pressure [75]. In particular, Dionaea muscipula, the Venus flytrap, has drawn strong interest from engineers and plant biologists alike.…”

Advances in passively driven microfluidics and lab-on-chip devices: a comprehensive literature review and patent analysis

“…145 In addition to that, selection of a suitable membrane is necessary to maintain the pH and to avoid clogging when biological cells or biomolecules are used. 143 Hence, capillary-based passive ow techniques are used as they depend only on the design and material characteristics of the MFD. On the other hand, in some instances, due to a drop in ow rate, essential pressure prediction at each step decreased sensitivity in capillary-based passive ow techniques.…”

“…142 Bruhn et al demonstrated the development of devices that are capable of pressure generation based on the osmosis principle, which could be made from available low-cost materials. 143 Some MFD and LOC devices using osmosis as a passive approach for their operation are shown in Fig. 6.…”

Glomerular protein separation as a mechanism for powering renal concentrating processes

“…The energy for ultrafiltration is derived from the hydrostatic pressure originating in the cardiovascular system. Osmotic separations constitute real and usable stored energy, and mixing may be used to recover this energy as work [22], [23], [24]. Indeed, industrial-scale osmotic energy storage and harvesting are being tested [23].…”