Robot production scenario

Steps towards a nano-robot

The results of PACE offer to proceed not only on the way towards evolvable single-vesicle systems, but also to make a step towards multi-cellular aggregates that show autonomous and controlloable behavior: a vesicle based nano-robot. The development of such a nano-robot profits from PACE and PACE-related work in many respects; crucial steps have been achieved with respect to a) consturction, b) actuation and c) functionalization of multicellular structures. We believe that there are several possible fields of applications e.g. environmental remediation or medicine. The idea to use chemically activated vesicles for the degradation of toxins in waste areas is rather obvious. But as long as the whole area must be covered with such mini-reactors, many questions, not the least economical ones, remain open. The situation changes as soon as these reactors become mobile. Then, working with ecologically and economically reasonable amounts of agents may be sufficient to achieve the necessary level of cleaning.


Actuation

The autonomous and controlled movement of nano- and micro-scale oil droplets in aqueous media have recently been demonstrated (Martin M. Hanczyc, Taro Toyota, Takashi Ikegami, Norman Packard, and Tadashi Sugawara. Fatty acid chemistry at the oil-water interface: Self-propelled oil droplets. JACS, 129:9386-9391, 2007). In this system the oil droplet agent can be thought of as a very small, chemically embodied soft matter robot. The agent is a synthesis of the following components: a motor based on an internal convection cell within the oil phase triggered by a Marangoni type of instability; the oil water interface acts as a very sensitive and dynamic sensor for the system; added surfactants that self-assemble at the interface between the oil droplet and water act as a link between the motor and the sensor, embedded chemistry within the oil droplet will fuel both autonomous movement and the processing of external chemical signals.


Construction of multivesicular structures for nanorobotics

An incremental approach was chosen. First, the vesicle should be linked in a programmable way allowing the positioning of vesicles with different content (functions, sensors, actuators). Then mechanisms for actuation, sensing and coupling of the two were investigated. 


One of the main problems to overcome is given by the fact that the building blocks of the nano-robots under consideration are on one hand too small to be assembled into multivesicular structures by external means but on the other hand are too big for being positioned solely by Brownian motion. Furthermore, vesicles-specific phenomena, such as the occurence of an effective repulsive force due to entropic effects between soft membranes (resulting in the so called Helfrich force) had to be considered. As detailed in the result section, PACE provides partially novel tehcnologies for the resolution of these problems. Besides the direct applicability in the field of nano-scaled and vesicle-based robotics, these results will also be of importance in the area of production technology of bio-inspired materials.


Sensing and Functionalization

Based on the outcomings of PACE, we are presently implementing a temperature sensor within vesicles (by the generation of temperature dependent pores), which then will trigger the chemical actuation of the oil droplets. Such temperature-dependent porous membranes can be produced by mixing 1,2-di-myristoyl-sn-glycero-3-phospocholine (DMPC), 1,2-di-palmitoyl-sn-gylero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Using the different phase transition temperatures of these PCs, an efflux of H+-ions out of the vesicles to the ambient space around the vesicle-oil-droplet-hybrids will trigger these actuators. 

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