## 2 Related Work
### Hand-Worn Clothing-Based Interfaces  
The human hand is primarily used to interact and manipulate real-world objects in our everyday life. Hence, it is not surprising that hand gestures, involving hands and fingers, are repeatedly studied in interactive systems (e.g., [25; 26; 40; 41]). Glove-based interfaces--the most popular systems for capturing hand movements--started nearly thirty years ago, and are continuously attracting the interest of a growing number of researchers. Glove-based input devices remove the requirement of the user to carry or hold their device to perform interactions. They are implemented by directly mounting different types of sensing technologies on the hand, mostly on each finger. The development of fabric-based strain sensing technology allows strain sensors to be either sewed or attached to the hand glove to detect the hand or finger movements [25; 41; 42]. Notably, [PERSON] et al. [42] proposed a glove system to enter inputs using users' thumb with two approaches: (1) by tapping ring and little fingertips with the thumb or (2) by sliding the thumb over the entire palmar surfaces of the index and middle fingers. Their proposed glove consists of both conductive and non-conductive fabrics, supporting both discrete and continuous output. They used two different approaches: (1) the palmar sides of both index and middle fingers are completely covered with grid conductive threads woven in an over-and-under pattern and (2) pads of thumb, ring, and little fingers are covered in conductive fabric. Typically, their glove-based input acts like a set of switches which can be closed by making contact with the thumb. This approach allows the glove interface to detect tap inputs on any fingertip and swipe gestures are performed on the conductive grids on both index and middle fingers. While their approach sounds promising for single-handed eyes-free interactions, the authors reported, however, that their sensing technology provided inaccurate results. [PERSON] et al. [25] presented \"Argot\", a wearable one-handed keyboard glove which allows users to type English letters, numbers, and symbols. Argot is made of multiple polyester or spandex blended stretch knit and textile patches which provide breathability and mobility. It employs conductive thread and textile conductive patches which improve user comfort and utilizes a simpler input language. The patches are installed on 15 different locations on finger pads (5 patches on each digit), fingernails (4 patches except thumb), and sides of the index, middle, and ring fingers (2 patches on each finger side). In addition, it provides both tactile and auditory feedback through magnetic connection. A layering system is developed to enclose the magnets within the conductive patches. All these materials are insulated using fusible stitchless bonding film. However, the authors reported that the users were always accidentally triggering the side buttons on the index, middle, and ring fingers while performing gesture inputs. Thumb-to-finger interaction methods present a promising input mechanism that is suitable to perform subtle, natural, and socially acceptable gestures. In particular, prior studies on hand gestures [35; 43] have found that both thumb and index fingers are preferred over the middle, ring, and pinky fingers. As explained by [PERSON] et al. [43] the thumb is opposable and has the ability to rotate and be able to touch other fingers on the same hand. Similarly, the muscles involved in moving each finger and the biomechanics make the index finger well suited for independent movement [35]. In particular, [PERSON] et al. [24] proposed \"Timmi\", a finger-worn piezoresistive fabric-based prototype which supports thumb-to-finger multimodal input. Timmi comprises of elastic fabric (made of 80% Nylon and 20% Spandex) painted with conductive elastomers and conductive threads. Diluted conductive elastomer was used to transform a normal fabric into a piezoresistive fabric.