## 1 Introduction  
Humans, vertebrate animals and robots use sensory inputs to interact with their environment [1; 2]. Tactile sensation is an important sensory input because it helps vertebrate animals and robots to better understand their surrounding environment, enabling them to intelligently interact with it [3; 4]. For example, the time duration between the moment a cat's whiskers touch an object and then identify it as a mouse to the moment the cat grasps its nape is about one-tenth of a second, even if the cat is blindfolded [4]. While vertebrate animals have biological tactile sensors, humanoid robots, unlike vertebrate animals, lack the ability to either replicate autonomous goal-directed movements or extract salient information from complex environments [5]. Psychophysical studies have shown that the ability of trained rodents to discriminate between fine textures, using their whiskers, is comparable to that of humans using their fingers tips [6]. This research aims to develop better tactile sensor systems to overcome limitations of other modes of sensing. For a detailed review of the current state-of-the-art in tactile sensor design, refer to [7]. We have chosen biological whiskers as our benchmark example. These rodents are known to have the ability to distinguish between different surfaces having different textures and shapes, using their whiskers [8; 9; 10; 11; 12]. Hence, whisker-based somatosensory systems appear to be well-suited for acquiring complex sensory information quickly and reliably [13]. Rodents and vertebrate animals sense by moving their whiskers rhythmically across the target surfaces to obtain tactile stimuli from the environment [5; 9; 14]. This rhythmic movement is reported to have a frequency ranging between 5 and 11 Hz [6; 15; 16; 17; 10]. However, the newer studies have shown that the frequency range is between 5 and 25 Hz [18; 19; 20; 10], and is called 'whisking'. Whisking excites several hundred primary afferent fibers, which innervate mechanoreceptors on each whisker shaft [21]. These signals, traveling via sensory nerve afferents, then reach the brain [8], as shown in Figure 1. The fundamental frequencies depend on the whisker length, ranging from 35 Hz for long whiskers to 110 Hz for short whiskers [9]. Table 1 summarizes the state of the art related to the handful of whisker mimicking inspired tactile sensor designs reported in the literature. [PERSON] and [PERSON] developed four whiskers made of Nickel Titanium (Nitinol) [5]. Each of the whiskers was mounted in a set of screws, with two opposing strain gauges to measure the movement of the whiskers. The set of screws were then mounted on a bar attached to a motor. A similar approach was adapted by [PERSON] and [PERSON] [22]. Their design consisted of 0.5 mm steel shafts coupled with Hall-Effect sensors to sense movement. These whiskers were mounted on a Koala platform and were moved using a DC (direct current) motor. Other groups used real mouse whiskers coupled with capacitor microphones [23; 24; 25]. These studies showed that such systems are useful for texture discrimination. However, all of these proposed designs had limitations due to bulky construction, lower frequency response due to transduction methods and their inability to give precise macro-motions due to use of DC motors for whisker motion. The ability to give macro motions is important, as previous studies have shown that in anesthetised rodents, whisker movement over surfaces results in a high frequency micro-motion superimposed on the macro-motion of whisking [8]. In this paper, we present the modeling, design, fabrication, and testing of a bio-inspired, mouse whisker mimicking tactile sensor that aims to overcome these limitations. A microcontroller-based control system has been implemented. This not only enables the vibration frequency of the whisker shaft to be controlled but also enables it to perform a desired vibrat  
Figure 1: Rodents and vertebrate animals sense the environment by moving or whisking their whiskers rhythmically across nearby surfaces.