Assembly of Nanostructures for Taste Sensing

Taste and smell are the two human senses that are chemical in nature. However, they have not been as successfully replicated with sensors, probably because of the ­complexity of the human system [1]. Although the science behind taste is still not fully elucidated, it is known that it relies on a series of taste cells densely packed in taste buds mainly located on the tongue and palate and in the pharynx. These taste buds are ­connected to nerve fibers that carry the signals of the chemical environment to the brain stem, where central processing of the information occurs [2]. It is commonly accepted that humans distinguish at least five basic taste qualities: saltiness, sourness, bitterness, sweetness, and umami, although some consider this model too simplified [3]. The “electronic” counterpart of tongues is an array of chemical sensors through which a raw signal output is transferred to a computer system and the data are processed. As an analogy to nature, it is generally assumed that taste sensors have to rely on sensors with a rather broad or relatively low chemical selectivity [4]. This philosophy is also supported by IUPAC in a technical report on electronic tongues [5]. The artificial tongues are dedicated to the automatic analysis of complicated composition samples, to the recognition of their characteristic properties, and to fast qualitative analysis.