Despite the wide range of applications and tremendous potential of implantable sensors targeting chemo/bio-markers, bringing actual practical devices fully to market continues to be inhibited by significant technological barriers associated with long-term reliability, which is a key requirement for implants. This is so, even with devices that appear to be well engineered, focused on apparently fairly solid markets, and based on well-established sensing principles. Wearable chem/bio-sensors offer an interesting approach, intermediate between the long-term vision of implantable devices, and the single use-disposable devices that are the current dominant use model. For example, wearable patch-type devices employing minimally invasive sampling of interstitial fluid for continuous glucose monitoring target a use period of about one week. However, despite this apparently rather modest target, large scale adoption is still frustratingly elusive, and products are being withdrawn from the markets [ ]. Moves by Google into the biosensing space are an interesting development, with the focus again being on how to gain access to sample fluids through which key biomarkers like glucose can be tracked in a non-invasive manner via a limited duration use model. Google are focusing on glucose monitoring through a contact lens that can be powered inductively (no batteries), can communicate wirelessly, function for 24 hours (lenses are changed daily), has an integrated electrochemical sensor, and is in contact with a sample fluid (aqueous humour) with glucose composition related (somewhat fuzzily) to that of blood [ ]. Similarly, the period up to the launch of the Apple iWatch witnessed a frenzy of speculation about whether it would have an integrated glucose monitoring capability [ ]. In the end, the iWatch was launched, with no mention of any integrated chem/bio-sensing capability.udHowever, once these initial applications are delivered, and the wearable platforms more clearly resolved, the drive for more value will place the spotlight on other sensing technologies that can implemented on-body to provide new types of information. In this respect, chemical sensors and biosensors are obvious candidates for integration. Clearly, however, these devices are inherently more complex and less dependable than the well-established physical sensors, as reflected in the difficulties in bringing these sensors to market [ ]. In this paper, I will examine the issues that currently limit the applicability of chemo/bio-sensors in wearable scenarios, and present ways through which these more complex sensors can be successfully integrated as part of a wearable sensing platform.ud
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