# A Soft, Biocompatible Magnetic Field Enabled Wireless Surgical Lighting Patty for Neurosurgery
## 3 Results  
The schematic illustration shows the anatomy of the surgical lighting device (Figure 1a). The surgical lighting patty consists of three layers: the central lighting layer and top/bottom surgical sponge. The device includes an actuating mechanism along the substrate or proximate to the power supply and electrically coupled to the power supply and/or light source. Here, a reed switch is configured to activate and/or deactivate power from the power supply when a magnetic source is positioned proximate to the actuating mechanism (Figure 1b). A reed switch makes physical contact in response to a magnetic field. The result allows a dramatically simplified wireless operation. Figure 1c,d  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Process** & **Purpose** & \ \begin{tabular}{c} **Required Time** \\ **for 10 Devices** \\ \end{tabular}  & **Equipment/Tools** & \begin{tabular}{c} **Progress** \\ **Level (\%) \(\ddagger\)** \\ \end{tabular}  \\ \hline
1. Preparation of & & & & \\ Copper/Polyimide film & & & & \\ on the glass & & & & \\  & & & & \\ \multirow{2}{*}{2. UV photo-lithography} & & & & \\  &  
provides visual evidence of the wireless operation enabled by a remotely located magnet. The wireless surgical lighting device can be extended to designs that incorporate more light sources in many sizes of a surgical patty (Figure 1d; right). A circuit diagram of the surgical lighting patty appears in Figure 2a,b highlights a signal flow from a power supply to light sources and captures the transient response. The circuit consists of three parts: a set of batteries, a toggle logic circuit, and lighting-emitting elements. A set of batteries powers a toggle logic circuit, the light emitting elements, and the control logic activates or deactivates LEDs. Here, an RC time constant, a measure of the ability of a circuit to respond to fast input signals and defined by the product of resistance (R4) and capacitance (C1), determines a transient response of the circuit [18; 19]. As we increase R4 and/or C1, the pulse width required for switching increases (Figure 2c). Plots of voltages at nodes of V1, V2, and V3 (S1) as a function of time provide details on transient responses (Figure 2d). Assuming that LEDs turn off, a set of batteries charges a capacitor, C1, through R1 and R2 resistors (Figure 2e). When a reed switch, denoted by S1, closes in response to a magnet, electrical charges stored at C1 release through a resistor, R4. This induces a voltage drop across R4, and subsequently turns on a transistor, NMOS2, (Figure 2f). Then, NMOS2 provides a signaling pathway for the LEDs, and the LEDs light up (Figure 2g). Consequently, an activation of the NMOS2 transistor enables PMOS and NMOS1 transistors, and this prevents charging through C1 (Figure 2h). Procedures for deactivation are reversible (Figure 2i). A reed switch causes the gate voltage of NMOS2 to move away from the threshold voltage when we place a magnet in an attempt to deactivate the device (Figure 2j). This results in deactivation of NMOS2 and no currents across LEDs flow, as shown in Figure 2k. Consequently, the signaling pathways of this route are changed toward C1, and a set of batteries charges C1 (Figure 2l). When a magnet is positioned proximate to a reed switch again, it activates LEDs. Video S1 provides visual evidence of the robustness of the operation. Figure 1: System overview of a surgical lighting patty. (**a**) Schematic illustration of a surgical lighting patty and (**b**) procedures for actuating mechanisms. (**c**) Image of a surgical lighting patty, next to a US penny coin. The surgical lighting patty is 1 mm thick, 12.7 mm wide, and 12.7 mm long. (**d**) Different sizes of surgical lighting patties (\(0.5\"\times 0.5\"\), \(0.5\"\times 1\"\), and \(1\"\times 3\"\); top to bottom, respectively) (left) and wireless operation (right). The topography of the surgical field, such as specific cavities or corridors, is uneven, narrow, or difficult in which to operate.