Smart Adhesives

The pads on the feet and/or legs of insects or animals such as beetles, spiders and geckoes have nanoscale hairs that enable them to attach and detach from different kinds of surfaces, allowing them to walk on them. These provide natural examples of reversible adhesion or smart adhesion. It has been suggested that the adhesion arises from a combination of van der Waals attractive forces and capillary forces (depending on the humidity) [103]. Synthetic surfaces comprising arrays of 400 X 600 nm nanopillars have been produced that mimic the gecko-foot effect with reversible adhesion for at least a few contact cycles [103]. 

In the new electronic stmctnres nnder development, interfaces between the various active materials will multiply many-fold. Adhesion in these cases does not merely involve mechanical contact, bnt also demands electronic, ionic, and optical integrity. Thns the stndy of adhesion will become more sophisticated to encompass these new demands. New stmctnred materials will emerge, often with complex self-assembled architectnres. At the nanometer level, it shonld be possible for an electronic device to come together by itself, driven by smart adhesion forces. 

Koberstein et al., J.T, Creating smart polymer surfaces with selective adhesion properties. J. Adhes., 66, 229-245 (1998). 

Many kinds of nonbiodegradable vinyl-type hydrophilic polymers were also used in combination with aliphatic polyesters to prepare amphiphilic block copolymers. Two typical examples of the vinyl-polymers used are poly(/V-isopropylacrylamide) (PNIPAAm) [149-152] and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) [153]. PNIPAAm is well known as a temperature-responsive polymer and has been used in biomedicine to provide smart materials. Temperature-responsive nanoparticles or polymer micelles could be prepared using PNIPAAm-6-PLA block copolymers [149-152]. PMPC is also a well-known biocompatible polymer that suppresses protein adsorption and platelet adhesion, and has been used as the hydrophilic outer shell of polymer micelles consisting of a block copolymer of PMPC -co-PLA [153]. Many other vinyl-type polymers used for PLA-based amphiphilic block copolymers were also introduced in a recent review [16]. 

Smart, J.D., Kellaway, I.W., and Worthington, H.E.C., An in vitro investigation of mucosa adhesive materials for use in controlled drug delivery, J. Pharm. Pharmacol36 295-299 (1984). 

When methyl 2-cyanoacrylate was applied as an adhesive to rabbit or human eyes, some reports described corneal haze and inflammation other reports with highly purified material indicated less toxicity. Mistaken use in the eyes as eyedrops has caused immediate brief smarting and firm gluing of the eyelids together. Acetone on a swab can be used to unglue the lids and remove the glue from the cornea with minimal, if any, injury to the corneal epithelium. ... 

Muscles contract and expand in response to electrical, thermal, and chemical stimuli. Certain polymers, such as synthetic polypeptides, are known to change shape on application of electric current, temperature, and chemical environment. For instance, selected bioelastic smart materials expand in salt solutions and may be used in desalination efforts and as salt concentration sensors. Polypeptides and other polymeric materials are being studied in tissue reconstruction, as adhesive barriers to prevent adhesion growth between surgically operated tissues, and in controlled drug release, where the material is designed to behave in a predetermined matter according to a specific chemical environment. 

Accutane must be prescribed under the System to Manage Accutane-Related Teratogenicity (SMART). The prescriber must obtain a supply of yellow self-adhesive Accutane qualification stickers. To obtain these stickers 1) Read the booklet entitled SMART Guide to Best Practices] 2) sign and return the completed SMART letter of understanding containing the prescriber checklist and 3) use the yellow self-adhesive Accutane qualification sticker. Accutane should not be prescribed or dispensed to any patient (male or female) without a yellow self-adhesive Accutane qualification sticker. 

Isotretinoin should be prescribed only by prescribers who have demonstrated special competence in the diagnosis and treatment of severe recalcitrant nodular acne, are experienced in the use of systemic retinoids, have read the SMART Guide to Best Practices, signed and returned the completed SMART letter of understanding, and obtained yellow self-adhesive Accutane qualification stickers. Do not prescribe or dispense Accutane without a yellow self-adhesive Accutane qualification sticker. 

Culturing of eukaryotic cells is an important element of modern life science. Although there are cells that can grow in free suspension, most cells derived from solid tissues need to be cultured at surfaces and must subsequently be lifted off for further use. Common protocols require the use of digesting enzymes like trypsin for this step, which will destroy any features outside the cell membrane. Hence, with these methods, harvesting of completely intact cells is impossible. Therefore, it was an attractive idea to apply smart polymer surfaces for the control of cell adhesion. 

Madsen, F., Eberth, K., and Smart, J. D. (1998), A rheological examination of the muco-adhesive/mucus interaction The effect of mucoadhesive type and concentration, I. Controlled Release, 50,167-178. 

Smart, J.D. An in vitro assessment of some mucosa adhesive dosage forms. Int. J. Pharm. 1991, 73, 69-74. 

Kakoulides EP, Smart JD, Tsibouldis J. Azocrosslinked poly(acrylic acid) for colonic delivery and adhesion specificity in vitro degradation and preliminary ex vivo bioadhesion studies. J Control Release 1998 54 95-109. 

---