A practical approach to the development of a synthetic Gecko tape

This paper describes the fabrication and the assessment of the adhesion of bio-mimetic Gecko hair arrays. These were fabricated using photolithographic methods of the type employed in the semiconducting industry and nano-moulding using silicon moulds. Specimens comprising mushroom shaped hairs were fabricated in polyimide and polydimethylsiloxane (PDMS), and also uniform cylinder shaped hairs were made in PDMS. Contact and separation distance between the hair surface and glass surfaces was assessed via the use of optical interferometry. Adhesion strength measurements were made using a simple, purpose-built balance. Multiple attachments were achieved on a range of surfaces including glass, and rough and smooth painted surfaces. Maximum loads were recorded for the mushroom shaped PDMS specimens on glass surfaces with strengths of up to 220 kPa. PDMS based structures were also found to exhibit time dependent adhesion strengths, and also adhesion strength which was a function of the number of reattachments. The mushroom shaped structures showed adhesion on glass with a contribution from molecular and atmospheric components. The material showed superhydrophobic properties. Cleaning experiments showed that simply washing with water could recover strengths after contamination with dust and foreign hairs.