Friction modulation allows for a range of different sensations and textures to be simulated on flat touchscreens, yet is largely unable to render fundamental tactile interactions such as path following or shape discrimination due to lack of spatial force distribution across the fingerpad. In order to expand the range of sensations rendered via friction modulation, in this paper we explore the possibility of applying spatial feedback on the fingerpad via differing friction forces on flat touchscreens. To this end, we fabricated six distinct flat surfaces with different spatial distributions of friction and observed deformation of the fingerpad skin in response to motion along these physical samples. In our study, friction changes that occur sequentially along the sliding direction introduced little transitory spatial warping such as compression or stretching to the fingerpad, suggesting limited perceptual differences in comparison to 'classic' friction modulation. Distributing friction across the direction of motion, however, showed pattern-dependent shearing of the fingertip skin, opening avenues for new sensations and illusions heretofore unachievable on flat touchscreen surfaces.

翻译：摩擦调制技术能够在平面触摸屏上模拟多种不同的触感和纹理，但由于缺乏在指垫上的空间力分布，该技术基本无法呈现诸如路径跟随或形状辨别等基础触觉交互。为扩展通过摩擦调制实现的触感范围，本文探索了通过在平面触摸屏上施加不同摩擦力来实现指垫空间反馈的可能性。为此，我们制备了六种具有不同空间摩擦分布的平面表面，并观察了手指沿这些物理样本运动时指垫皮肤的形变情况。研究发现，沿滑动方向顺序发生的摩擦力变化对指垫产生的瞬态空间扭曲（如压缩或拉伸）较小，表明其与“经典”摩擦调制相比感知差异有限。然而，沿运动方向分布的摩擦力则显示出依赖于图案的指尖皮肤剪切形变，这为在平面触摸屏表面实现以往无法达成的新触感与触觉错觉开辟了途径。