Stimuli-responsive interfaces

Stimuli Responsive Interfaces Obtained by Surface Segregation... 

Cole, M. A., Voelcker, N. H., Thissen, H., Griesser, H. J. (2009). Stimuli-responsive interfaces and systems for the control of protein-smface and cell-surface interactions. Biomaterials, 30, 1827-1850. http //dx.doi.Org/10.1016/j.biomaterials.2008.12.026. 

Sanjuan, S., Tran, Y. (2008). Stimuli-responsive interfaces using random polyampholyte... 

Multiple islands arranged on hemisphere. Each island houses a tunable liquid microlens formed by a curved water-to-oU interface pinned at the edge of a polymer aperture by surface tension. The change in the curvature of the interface is caused by stimulus-responsive hydrogel actuators. (Source Adapted from Zhu, D., Zeng, X., Li, C. and Jiang, H. 2011. Journal of Microelectromechanical Systems, 20(2), 389-395. With permission.)... 

The biological role of stimulus-responsive materials in general and peptide materials in particular are presented first, before discussing the importance of responsive interfaces and surfaces in biology. 

Abstract To appreciate the technological potential of controlled molecular-level motion one only has to consider that it lies at the heart of virtually every biological process. When we learn how to build synthetic molecular motors and machines that can interface their effects directly with other molecular-level sub-structures and the outside world it will add a new dimension to functional molecule and materials design. In this review we discuss both the influence of chirality on the design of molecular level machines and, in turn, how molecular level machines can control the expression of chirality of a physical response to an inherently achiral stimulus. 

Fig- 4.25. The difference in the concentration response to the stimulus of (a) a sink and (b) a source at the electrode-electrolyte interface. 

In design of electrochemical sensors (and biosensors) especially helpful is electrochemical impedance spectroscopy (EIS), providing a complete description of an electrochemical system based on impedance measurements over a broad frequency range at various potentials, and determination of all the electrical characteristics of the interface.60-61 Generally it is based on application of electrical stimulus (known voltage or current) across a resistor through electrodes and observation of response... 

In order to compare the response of the sensor interface with the ORN output spiking rate, they have been considered sensors with a resistance time evolution in presence of a step of chemical stimulus ruled by the equation ... 

FIGURE 3.1 An ALOPEX system. The stimulus is presented on the cathode ray tube (CRT). The observer or any pattern recognition device (PRD) faces the CRT the subject s response is sent to the ALOPEX interface unit where it is recorded and integrated and the fi nal response is sent to the computer. The computer calculates the values of the new pattern to be presented on the CRT according to the ALOPEX algorithm and the process continues until the desired pattern appears on the CRT. At this point the response is considered to be optimal and the process stops. 

Another important aspect of the zig-zag behavior is the detection of the edge of the plume and the absence of stimuli. We know from peripheral nerve recordings that the response of olfactory nerves does not totally adapt after prolonged exposure. Thus, the animal is presumably able to sense the off-set of a stimulus and would be capable of detecting movement out of the stimulus. However, there are other explanations of the animal s ability to detect the edge of the plume. These may include re-stimulation after rinsing out by the subthreshold water and a re-stimulation by suprathreshold water found at the discontinuously mixed interface. Experiments on the fish s ability to detect decreasing concentrations will be required to determine the actual mechanism of the release of zig-zag behavior. 

Apparent Mass of Seated Persons. The apparent mass is often used to describe the response of the body at the point of stimulation rather than the mechanical impedance, and is the complex ratio between the dynamic force applied to the body and the acceleration at the interface where vibration enters the body. It is commonly expressed as a function of frequency, and is equal to the static weight of a subject in the limiting case of zero ftequency when Ae legs are supported to move in unison with the torso. The influence of posture, muscle tension, and stimulus magnitude on the... 

Electrochemical impedance measurement systems used for the analysis of the ac properties of electrochemical cells typically consist of a potentiostat (sometimes called an electrochemical interface) together with a frequency response analyzer (FRA) or a spectrum analyzer, or even a combination of the two. The potentiostat provides buffered connections to the cell under investigation together with circuitry for applying a controlled voltage or current stimulus and for the measurement of the dc properties of the cell. The FRA is connected through the potentiostat to the cell and therefore the bandwidth of the potentiostat is a very important consideration for accurate high frequency analysis. 

PKA and AP, respectively (Wang et al 2010 Zelzer, McNamara, et al 2012), as well as the triggered availability of a peptide sequence on the surface (Todd et al 2009). As peptides are natural substrates for enzymes, enzymatic response of a peptide surface appears to be an ideal way to interface a biomaterial surface with a living system. Enzymatic stimulation of peptide surfaces has the advantage that the environmental conditions required (physiological conditions) are ideal for both the peptide and the stimulus. For applications in living systems, emphasis must be placed on a well-designed peptide surface to prevent unwanted interaction with other enzymes. 

Causality The response of a system should be solely due to the probing signal. Physically, this means that the system being tested responds fully and exclusively to the applied signal. This is an important consideration in electrochemical systems, because charge transfer interfaces are often active and do, in fact, generate noise in the absence of any external stimulus [15]. 

---